~f~L STABILIZATION FOR RENOTE AIRFIELDS
FINAL REPORT
by
Paul L. Koehmstedt Senior Research Scientist
Battelle, Pacific Northwest Laboratories P.O. Box 999 Richland, Washington 99352
January 1986
for
STATE OF ALASKA DEPARTMENT OF TRANSPORTATIO~ AND PUBLIC FACILITIES DIVISION OF PLANNING RESEARCH SECTION 2301 Peger Road Fairbanks, Alaska 99701=6394
TIle contents of this report reflect the views of the author who is responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views of policies of the Alaska Department of Transportation and Public Facilities. This report does not constitute a standard, speCification or regulation. ABSTRACT
/1, laboratory study has been completed which involved extensive testing of two soil samples from the Bethel, Alaska area to determine if these soils can be stabilized with a combination of cement and asphalt emulsions, for use as subbase and base course materials for airfield and roadway appli cations. Three cationic slow-set set (C55-1) emulsions from different manufacturers were compared. Two of these were of standard manufacture, and the third was produced after selecting an emulsion based on the zeta potential and surface area of the test soils.
Test results demonstrated that the use of an emulsion specially selected for the particular soil properties can result in major performance improve ments over standard production emulsions of the same grade. For the soils tested, similar strength levels were reached with 30 to 40% less of the specially select emulsion.
Cement contents between 0.5 and 2. O~~ were added to a seri es of so i 1- emulsion mixes. Cement contents below 1.5% were generally of no benefit and in several cases actually reduced strength values. Cement contents of 2% consistently increased the mixture cohesive strengths by 20 to 80%.
Tests of sands having different fines contents indicated that the optimum fines content for emulsion stabilization falls between 12 and 20 percent.
iii ACKNOWLEDGMENT
The assistance of Professor Ronald Terrel and Amir Ahmadi of the University of Washington, Civil Engineering Laboratory, in this program is gratefully acknowledged. Their performance beyond contractural agreement was commendable .
•
v CONTENTS
ABSTRACT . iii ACKNOWLEDGMENT v INTRODUCTION 1 PRIOR PROGRAM TESTS 5 PROGRAM OBJECTIVE 6 MATERIALS AND STABILIZATION CONCEPT. 7 LABORATORY TEST PROGRAM . 8 CHARACTERIZATION OF SOIL SAMPLES 12 MOISTURE CONTENT 12 AVERAGE ZETA POTENTIAL 13 AGGREGATE SURFACE AREA. 14 MECHANICAL ANALYSIS FOR SOILS (ALASKA T-l) 14 Particle Size Analysis of Soils (AASHTO T-27). 14 Hydrometer and Sieve Analysis (Alaska T-l) . 15 Specific Gravity (Alaska T-l) (AASHTO T-84) . 15 LIQUID LIMIT (ASTM D423-66), PLASTIC LIMIT AND PLASTICITY INDEX (ASTM D424-59) OF SOLIDS. 18 Moisture Density Relationship (AASHTO T-180, ASTM D1557) 18 ORGANIC CONTENT OF SOILS (ALASKA T-6) 21 Comparative Soil Characterization Data 21 ENGINEERING MEASUREMENTS, TEST SERIES 1 23 PRELIMINARY MIX DESIGN 25 CALIFORNIA BEARING RATIO (CBR) (ASTM D1883, AASHTO T 193-72) 27 HVEEM STABILITY AND COHESION (ASSHTO T-90) (ASTM D2844) 33 RESILIENT MODULUS (M ) 45 R
vii CONTENTS (Continued)
ENGINEERING MEASUREMENTS, TEST SERIES 2 50 PRELIMINARY DESIGN MIX 50 CALIFORNIA BEARING RATIO. 53 TEST SERIES 2 CBR SPECIMEN COMPOSITION 54 Hveem Stability and Cohesion 54
RESILIENT MODULUS (M R) SERIES 2 58 FROST HEAVE SUSCEPTIBILITY TESTS 60 Test Results 61 SUMMARY AND CONCLUSIONS 63 CHARACTERIZATION 63 ENGINEERING MEASUREMENTS 65 California Bearing Ratio (CBR). 65 STABILITY AND COHESION 68 FUTURE CONSIDERATIONS. 76 REFERENCES. 78 APPENDIX A - ASTM TEST METHOD D244-83a, EMULSIFIED ASPHALTS A.1 APPENDIX B - ASTM TEST METHOD D 2216-80, LABORATORY DETERMINATION OF \.JATER (MOISTURE) CONTENT OF SOIL, ROCK, AND SOIL-AGGREGATE MIXTURES B.1 APPENDIX C - ZETA POTENTIAL TEST METHOD C.1 APPENDIX D - AGGREGATE SURFACE AREA PART 1 - THE ETHYLENE GLYCOL MONOETHYL ETHER (EGME) TECHNIQUE FOR DETERMINING SOIL-SURFACE AREA D.1.1 PART 2 - DETERMINING SURFACE AREA . D.2.1 PART 3 - ADSORPTION OF GASES IN MULTIMOLECULAR LAYERS D.3.1 PART 4 - SURFACE AREA OF AN IRREGULAR SOLID, BET Gas Adsorption Method D.4.1
viii CONTENTS (Continued)
APPENDIX E - PROPOSED ASPHALT EMULSION COLD MIX DESIGN METHOD (Modification of the Marshall Method, ASTM 0-1559-82) . E.1 APPENDIX F - ALASKA FROST HEAVE TEST EQUIPMENT AND PROCEDURES F.1
ix FIGURES
1. Cationic Asphalt Emulsion Deposition. 4 2. Bethel Soil Test Sites. 9 3. Bethel Soil 10 Aggregate Grading Chart 16 4. Bethel Soil 20 Aggregate Grading Chart 17
5. Moisture-Density Relation Bethel Soil 10. 19 6. Moisture-Density Relation Bethel Soil 20. 20 7. Approximate Interrelationship of Soil Classification and Bearing Values 24
8. Soil 10 CBR Load Penetration 28 9. Soil 20 CBR Load Penetration 29
10. CBR and Density Plotted vs. Water Content 30
11. Test Series 1 Stability and Cohesion - Soil 10 41 12. Test Series 1 Stability and Cohesion - Soil 20 42 13. Design Chart for Thickness of Layers of Pavement Structure 44 14. Test Series 2 Moisture-Density Relationships . 51 15. Test Series 2 Stability and Cohesion - Soil 10 56 16. Test Series 2 Stability and Cohesion - Soil 20 57 17. Flexible Pavement Design Curves for Critical Areas, Dual Wheel Gear 66 18. Soil Support Value Correlations (5) 71
19. AASHO Flexible-Pavement Design Nomographs (5) 72
x TABLES
1. Moisture Content of Bethel Soils 13 2. Zeta Potential of Bethel Soils 13 3. Average Surface Area of Bethel Soils (EGME) 14 4. Particle Size Analysis of Bethel Soils (AASHTO T-27) 15 5. Specific Gravity Bethel Soils 15 6. Liquid Limit Bethel 2-20 . 18 7. Plastic Limit Bethel 2-20 18 8. Organic Content of Bethel Soils (Alaska T-6) 21 9. Comparative Bethel Soil Characteristics, % Passing Designated Screens 22 10. Preliminary Mix Design 25 11. Test Series 1, Specimen Preparation Matrix 26 12. California Bearing Ratio (Soaked, %) 31 13. Equivalency Factor Range for Stabilized Subbase 32 14. Equivalency Factor Range for Stabilized Base 32 15. Test Series 1, CBR, Soil 10 33 16. Summary of Test Data - U.S. Oil 504, Bethel Soil 10 35 17. Summary of Test Data - ARMAK E4868, Bethel Soil 10 36 18. Summary of Test Data - Chevron CSS-1, Bethel Soil 10 37 19. Summary of Test Data - U.S. Oil 504, Bethel Soil 20 38 20. Summary of Test Data - ARMAK E4868, Bethel Soil 20 39 21. Summary of Test Data - Chevron CSS-1, Bethel Soil 20 40 22. Specimens for Resilient Modulus, MR' 46 23. Summary of Resilient Modulus Tests for Bethel Soil 10 47
xi TABLES (Continued)
24. Summary of Resilient Modulus Tests for Bethel Soil 20 & Blend 48 25. Test Series 2 Mix Designs. 52 26. Test Series 2 Specimen Preparation Matrix 53 27. CBR Results, Test Series 2 54 28. Test Series 2 Hveem Stability and Cohesion Test Data 55 29. Resilient Modulus Test Data, Soil 10 59 30. Resilient Modulus Test Data, Soil 20 59 31. Frost Heave Specimen Composition 60 32. Frost Heave Specimen Water Content 61 33. Comparative Soil Specific Gravity 63 34. Modified Proctor Density . 64 35. Particle Size Distribution of Bethel Soils 64 36. Pavement Course Thickness Requirements (Crushed Aggregate) 65 37. Pavement Course Thickness Requirements (Asphalt-Cement). 67 38. Stabilization Materials Requirements 67 39. Approximate Runway Material Costs 68 40. Structural Layer Coefficients Developed From Various Sources. 73 41. Approximate Materials Requirements/Mile 74
xii I NTRODUCT ION
The Yukon and Kuskokwim delta areas of Western Alaska lack gravel or bedrock suitable for airfield or roadway construction. Gravel must be imported by barge from sources considerable distances away. There is, then, an obvious benefit in using on-site materials as much as possible to minimize gravel importation. Sands of all types are plenti ful in this area of Alaska but they are poorly graded and are unusable as bases to support runway or roadway pavement. After freezing and thawing, the untreated soils of this region become unstable and non supportive of the wheel loadings on overlying coarse gravel or paving. Roads within this area of Alaska are unpaved and subject to exces sive erosion and hazardous conditions during thaw or rainy periods. Some 300 airstrips within this region depend upon natural grass growth for stabilization and erosion control. Consequently, both airfields and roads have limited ability to support vehicular weight during the warm season and even less during thaw or wet conditions. Admixed gravel, normally used where only poorly graded fine sand or silty sand prevails, is essentially unavailable and must be imported by barge from consider able distance at great expense. Sand stabilization-in-place by admixing of stabilization agents with on-site sand or silt appeared to be a financially viable alternative. Only low cost, low concentration asphalt emulsions and Portland cement stabilizers were considered. Lime, another low-cost stabilizer, is useful primarily in clayey soils which are rare in Alaska. Asphalt emulsion-soil mixtures must be especially adapted to Alaskan conditions. Asphalt emulsions, which typically contain 25 to 40% by weight water, are considered impractical to use in cold, wet climates. After emulsion addition the asphalt attaches to the aggregate surfaces and the residual water must dissipate via evaporation or percolation until a low level admixture water content remains. Controlled water level is necessary as a lubricant during compaction of asphalt emulsion soil admixtures. Cure times of ambient temperature emulsion-aggregate admixtures are long and often unpredictable in Alaskan environments.
1 With the advent of the mobile emulsification plant, hot emulsion (about 130 to 150°F) can be used. This reacts much more rapidly with sandy soils, forming hydrophobic admixtures which expel residual water. Cure times are shortened and therefore the entire process may be more suitable for Alaskan applications. On-site emulsification has the additional attractive feature of using on-site water which saves up to 40% of the asphalt emulsion transportation costs. The use of hot emulsion with ambient temperature sands is a viable mixing method of use in Alaskan applications. The moisture content of sands involved in asphalt emulsion addition is critical. Typical Alaskan soils, particularly thavled permafrost, may be too high in water content for optimum stabilization usage. Atmospheric drying appears impractical in Alaska, particularly from a standpoint of a crowded schedule in a short summer. It may be practical to use a drum-dryer to lower the water content to optimum values followed by covered storage. Portland cement may be added to the input damp sands to react with the excess moisture in lieu of the drum-dryer operation. Portland cement bonds to the aggregate forming irregular surfaces and increases the aggregate-aggregate bonds; cement also accelerates admixture curing. The bonded and irregular surfaced aggregates perform as better graded mixes during compaction. Preliminary selection of the asphalt emulsion can be based upon many factors but is ultimately based upon laboratory tests. The labora tory testing program not only establishes the component mix ratio and mixing time, but should be able to predict performance of final product. Asphalt emulsions are categorized according to charge, i.e., cationic (positively charged), non-ionic (uncharged), and anionic (negatively charged). Since most soil and aggregates encountered to date on airfield and road construction throughout the world are anionic in nature, cationic asphalt emulsions are commonly used to achieve electrostatic bonding. Asphalt emulsion is manufactured in a colloid mill by combining molten asphalt (at 250°F) with water at 150°F containing 1 to 2% emulsifier. A typical commercial asphalt emulsion contains by weight 60% asphalt, 38% water, and 2% emulsifier. Higher asphalt content
2 emulsions, particularly cationic, are manufactured but have decreasing storage life as asphalt content is increased. The emulsifier coats each asphalt particulate (micelle). The emulsifier is chemically synthesized to impart the desired charge type (positive, uncharged, negative) to each asphalt micelle. Furthermore the emulsifier can be chemically synthesized to provide various degrees of charge intensity to the asphalt micelle. Charge intensity is measured by zeta meter, a common article of equipment found in the colloid science laboratory. The zeta meter is basically a charged, illuminated aqueous field which may be observed through a microscope. Zeta potential of a colloid is the voltage potential in millivolts necessary to move the charged particle one centimeter in one second. Asphalt colloids (emulsions) have been manufactured with zeta potentials which range 0 to 120 mv cationic and 0 to 85 mv anionic. Maximum potentials are both well beyond the zeta potential range of any colloid found in nature. Interaction of the asphalt emulsion with aggregate varies consider ably with charge type and charge intensity. On dehydration, non-ionic and anionic asphalt emulsions form mechanical bonds with the anionic aggregate similar to the well-known hot asphalt-aggregate bond. No electrostatic bonding is involved. The coated aggregate is converted from a hydrophilic to hydrophobic condition. In the case of the cationic asphalt emulsion, the micelle is attracted electrostatically to the aggregate surface as depicted in Figure 1. The asphalt micelle with a 1.5 x 106 average molecular weight is much too large to directly contact the anionic deposition site for quantitative charge neutral ization encountered in inorganic chemical reactions. The formed electrostatic bond is, however, very strong, and requires dissolution by hydrocarbon solvents or saponification by hot caustic for destruction. Such a bond is much less susceptible to cyclic freeze-thaw (stripping) damage than the conventional mechanical bond. (2) Asphalt emulsions available to the engineer are categorized as cationic rapid set (CRS), cationic medium set (CMS) , cationic slow set (CSS), anionic rapid set (RS), anionic medium set (MS), anionic slow set (S5-1) and uncharged emulsion. The rapid-medium-slow set designation is in fact a range of zeta potentials. The higher the zeta potential the more rapidly electrostatic bonding occurs. Upon electrostatic 3 Asphalt Droplet
Water
Deposited Asphalt
FIGURE 1. Cationic Asphalt Emulsion Deposition
bonding the aggregate is converted from a hydrophilic to a hydrophobic surface condition which results in expulsion of water. When first applied, the cationic asphalt emulsion appears brown in color, turning black upon bonding (setting). Specifications of asphalt emulsion manufacture are subject to varying interpretation. For example, CS5 emulsion must meet a minimum asphalt content, must meet a pH range, but is not required to be cationic even though the emulsion is marketed as cationic slow set (C5S). The particle charge test (ASTM 0244), used to verify the cationic state, has been troublesome with low zeta potential emulsions and is presently in a state of modification. In addition to the aggregate zeta potential as a factor in cationic asphalt emulsion selection, aggregate surface area must be considered. One rule of thumb used in mix design is: low aggregate zet'a potential--high zeta potential emulsion. With high aggregate surface area--use a low zeta potential emulsion. Aggregate surface area dominates over aggregate zeta potential in nearly all cases. Aggregate water content is also important: too low and the aggregate dehydrates the
4 emulsion causing breaking before electrostatic bonding can take effect; if too high, a dilution results which prevents total aggregate coverage.
PRIOR PROGRAM TESTS A previous two year program, "Soil Stabilization for Remote Area Roads,I/(l) was conducted by the State of Alaska to determine if asphalt emulsion and Portland cement could be used to improve stability of Yukon-Kuskokwim area sands and silty sands for use as subbase and certain surface applications. The asphalt emulsions furnished by Chevron USA, Inc., were SS-I, CSS-l, and CMS-2S. The l~tter emulsion contains a small amount of solvent for improved wetting purposes. Of the three emulsions tested, CSS-l provided the more stable mixes, followed by SS-I. In the present study, limited to two Bethel sands, Chevron USA, Inc., CSS-l was a requirement; two other emulsions were optional. Anchorage Chevron which supplied CSS-l to the previous program could not supply this test program but made arrangements for Chevron at Portland, Oregon, to prepare the same emulsion. Use of Chevron Anchorage CSS-l will allow some comparisons of the two Bethel sands in each program.
5 PROGRAM OBJECTIVES
The a rea of ~ies tern Alas ka formed from the de ltas of the Yukon and Kuskokwim Rivers and known as the Delta Region, is nearly devoid of gravel usefu 1 for pavement app 1 i ca t ions, but abounds in poorly graded sand and silty sands. The primary objectives of this program were to determi~e if these sands could be adequately stabilized for use as subbase and base course materials for airfield applications, and to investigate the benefits of clistom-formulated emulsions prepared for the site-specific soil s .
6 MATERIALS AND STABILIZATION CONCEPT
The most cost-effectivE use of stabilization procedures would be to treat on-site soils with travelling mixers which can inject asphalt emulsion during a tilling and mixing operation. Cement addition could be done by spreading a uniform layer of cement on the soil surface ahead of the k' travelling mixer. Following one or more passes of the tiller-mixer, the soil would then be ,aerated if necessary and recompacted. Accurate data on field moisture contents is necessary to design a stabilization program which allows for the initial moisture in the soil. If soils must be ;, transported to and from a fixed mixer or dr'um-dryer, the costs rapidly approach those of imported gravels.
Thi s study has dernonstra ted the benefits of us i ng 1abora tory tes ts to select the emulsion and cement contents and also the emulsion type. [)ifferent emulsifiers appear to react very differently even though the resultant emulsiors meet the same specifications. Further economies will be realized in remote areas on larger projects by on-site preparation of the emulsion. This reduces the expenses of shipping, since only the asphalt component need be shipped in. The 25 to 40% water component of the emulsion can be obtained locally. A trained emulsion-mill operator is, of course, required.
7 LABORATORY TEST PROGRAM
A laboratory test program was conducted by Battelle, Pacific Northwest Laboratories (BNW) to establish the feasibility and to evaluate the mechanical stability of stabilized soil. Portland cement and asphalt emulsion were added to poorly graded Bethel soils to improve their pavement support capability. The two soils tested are believed to be typical of the Alaskan Delta regions. They are abundantly available, whereas this region is essentially devoid of satisfactory gravel materials. This laboratory test program goal was to upgrade these soils by sequential cement and asphalt emulsion addition for use as subbase and base course materials in airport and highway applications. The relatively thin surface course requires gravel for performance as a wear surface. The total gravel import requirements could be drastically reduced by this concept. Soil samples were taken from the Bethel airport site as shown in Figure 2 and shipped to Battelle in canvas bags. Ten bags of each soil containing approximately 85 pounds each were identified as 1-10 through 10-10 and 1-20 through 10-20. Single bags were used for soil character ization. For engineering measurements, three bags from each soil source were combined and mixed (for homogeneity purposes). The emulsions selected for this test program were based upon the following rationale. For correlation purposes, a Chevron Anchorage-produced CSS-1 emulsion used in a previous State of Alaska DOT&PF program(l) was required. This emulsion was unavailable from the Chevron Anchorage facility, but emulsion samples of the same formulation were obtained from the Portland Oregon Chevron faci.lities. U.S. Oil and Refining Corporation at Tacoma supplied two CSS-l asphalt emulsions. These were CSS-l (504) and CSS-1 (722). The minor difference between the 504 and 722 formulations of CSS-1 did not warrant testing both, therefore the 722 Type CSS-l was eliminated from further testing early in the program. Selection of the third emulsion was made after surface area and zeta potential measurements were made on the Bethel soil samples. Measurements were made at both BNW and the AKZO Chemie America Laboratory 8 TH~OA \ o \ TH! 7.0. Th20},. 0 0 -y , TH9A \ 5 TH 18t. -----=:::--
THI9A ," ,!4~",. ~_\_'50 ~i: Soil 20 Site
-'
" ,! / ,. -- --.' , , , '", ~' --~-V
FIGURE 2. Bethel So; 1 Test Sites in Chicago. The data agreed quite well. ARMAK Redicote E4868 (supplied by AKZO Chemie America) was selected as the available cationic asphalt emulsifier best matching the Bethel sands. ARMAK E4868 is a material of low zeta potential well known for its ability to coat fine, high surface area aggregate, and also is the most stable of the ARMAK cationic emulsions in the alkaline environment created by the addition of Portland cement. Emulsion suppliers were requested to use AC 5 grade asphalt and about 60% by weight asphalt in emulsion preparation in order to put all emulsions on a common basis. The selected emulsions were subjected to a charge deposition test, ASTM 0244, to indicate degree of cationic behavior. Small (I-inch wide, 1/16-inch thick) stainless strips were immersed I-inch deep into the as-received emulsions. The pre-weighed strips were separated 0.5 inches in all three emulsion tests. A high capacity 12 volt dc source was placed between each electrode pair for exactly 30 minutes. The electrodes were removed from the emulsion while still charged, disconnected from the dc source, and allowed to air dry. Oven drying and reweighing determined the asphalt deposition on each of the electrodes. This experiment showed the samples of Chevron CSS-l and U.S. Oil and Refining CSS-l (504) to be nearly non-ionic, and AR~AK E4868 to be definitely cationic. Experimental data is tabulated in Appendix A. Type I Portland cement was admixed onto the damp aggregrate prior to introduction of the emulsion. The function of the cement is to 1) form irregular surfaces on the similar-sized, round sand particles, 2) form some bonds between sand particles to further improve the aggre gate grading mix, and 3) absorb and combine with the excess water from the emulsion. With irregular surfaces and variable particle size, more effective compaction can be achieved resulting in a greater load-bearing material. Cement also accelerates the emulsion set time, which is valuable in the cold climate applications. The laboratory test program was divided into two parts, i.e., soil characterization and engineering measurements. The soil characterization data was obtained at the Battelle, Pacific Northwest Laboratories with supplemental data from the AKZO Chemie America (formerly ARMAK) Laboratories in Chicago. This data was 10 forwarded to the University of Washington for use in engineering measure ment specimen preparation. Engineering measurements were obtained by the University of Washington Civil Engineering Laboratory by subcontract B-H1246-C-P. Data from the Battelle compaction/stability measurement equipment (Marshall) was not convertible to sponsor-required Hveem compaction/stability values. The specimens tested at the University of Washington Civil Engineering Laboratory were prepared locally using a Battelle-supplied procedure because there was concern that specimen characteristics might change during transportation from Richland to Seattle.
11 CHARACTERIZATION OF SOIL SAMPLES
BNW characterization of the Bethel soils included: 1. Moisture Content (ASTM D2216-BO) 2. Average Zeta Potential 3. Average Aggregate Surface Area 4. Mechanical Analysis for Soils (Alaska T-l) 5. Organic Content of Soils (Alaska T-6) 6. Sieve Analysis (Alaska T-7) 7. Moisture-Density Relation, Proctor, (AASHTO T-IBO-D) These procedures or their ASTM or AASHTO equivalents were utilized to characterize the Bethel soils. If chemical additives improve the mechanical properties of the Alaskan soils under test, we can reasonably expect to extrapolate the stabilization process to other soils. The amounts and kinds of additives required for successful soil stabilization will change as the properties of the soil change. The soil characterization undertaken in this program is a first step in correlating Alaskan soil properties with optimized soil stabilization treatment. The soil characterization used in this program depends on standard tests developed for other purposes than the present. It is not yet demonstrated that the correct character ization tests were used or that all the relevant properties were measured.
MOISTURE CONTENT The primary purpose of this test was to verify that the soil contains adequate moisture to eliminate dehydration of the emulsion by the soil. Dehydration results in emulsion segregation ard poor soil-to-asphalt bonding. The soils samples were shipped in canvas bags which could have led to considerable moisture change(s) during transit. "As-received moisture content" is calculated in Table 1.
12 TABLE 1. Moisture Content of Bethel Soils
Bethel Soil Sample % Water Average % Water 1 - 10 a 0.56 0.49 b 0.46 c 0.46 2 - 20 a 1.56 1.63 b 1.48 c 1.85
The low water content of the samples would have dehydrated the asphalt emulsion; therefore, water was added to the soil prior to \:. emulsion addition. Two to 4% water is usually optimum as a starting 7:! " ( pOint for trial test mix design. The test method and data are tabulated in Appendix B.
AVERAGE ZETA POTENTIAL The soil zeta potential measurement, a vital piece of information in asphalt emulsion selection, was obtained using the procedure supp1iea with the zeta potential measurement equipment. A description of the test method may be found in Appendix C. Summarized zeta potential measurements appear in Table 2.
TABLE 2. Zeta Potential of Bethel Soils
Average Zeta Zeta Potential Potential Bethel Soil Sample (mv) (mv) 1 - 10 a -27.1 -26.3 b -23.3 c -28.6 2 - 20 a -30.0 -34.2 b -38.8 c -33.8 8 - 10* -24.5 10 - 20* -24.5
*AKZO Chemie America data. 13 The variability of Bethel Soil 2 is presumably representative of different samples (bags), 2-20 and 10-20, taken from the same area. A small difference in silt content could readily explain the difference in zeta potential measurement data. This difference was not a factor in selecting a cationic asphalt emulsion.
AGGREGATE SURFACE AREA The aggregate average surface area, the second piece of information necessary to select a specific cationic asphalt emulsion of known zeta potential, may be measured by one of two methods, 1) the volume of nitrogen physically adsorbed on soil surface at constant temperature and various pressures, or 2) the amount of ethylene glycol monomethyl ether (EGME) adsorbed on soil surfaces at constant temperature. Both methods are described in Appendix D; only the EGME absorption method was used here as tabulated in Table 3.
TABLE 3. Average Surface Area of Bethel Soils (EGME)
Average Surface % Passing Sample Area m2/g #200 Sieve 1 - 10 1.70 7 29 2 - 20 12.40
MECHANICAL ANALYSIS FOR SOILS (ALASKA T-1) Particle Size Analysis of Soils (AASHTO T-27) Since all material readily passed the No. 10 sieve, the AASHTO T88-78 procedure was substituted for AASHTO T-27 to include additional screens for further size distribution information. Dry sieve distribution is tabulated in Table 4.
14 TABLE 4. Particle Size Analysis of Bethel Soils (AASHTO T-27)
Sample Sample Sample Sample Sample Sample 1-10** 2-10* 8-10* 2-20*** 4-20* 10-20**
Sieve # % Passing 10 100 30 100 100 100 40 99 99 100 100 50 95 96 94 98 98 99 100 52 40 69 62 200 7 6 8 29 20 26 325 1 4
* ARMAK data. ** University of Washington data. ***Battelle-Northwest (BNW) data.
Hydrometer and Sieve Analysis (Alaska T-1)
') Wet sieve analysis for Samples 1-10 and 2-20 are shown in Figures .; and 4, respectively.
S~ecific Gravity (Alaska T-1) (AASHTO T-84) The specific gravity measurements of Bethel soils which a re tabu 1a ted in Table 5 were obtained using the AASHTO T-84 procedure.
TABLE 5. Specific Gravity Bethel Soils Specific Gravity Sam~le g/cc Average • Bethel Sample 1-10* a 2.70 b 2.68 2.69 apparatus/broke Bethel Sample 2-20* a 2.70 b 2.73 2.72 c 2.72 Bethel Sample 2-10 2.70 Bethel Sample 4-20 2.70 * Battelle-Northwest data. **ARMAK data. 15 Sieve No. Square Openings 270200 100 50 30 16 8 4 3/8" 3/4" 1-1/2" 3" 100
90
80
70
OJ c ~ C Ql u 50 ...... Ql Q) 0- co ~ 40 0 f- 30 20 . Sample No: #8-10 (#10) Source: Bethel, Alaska 10 Materials: Silty Sand 0 0.001 • 0.01 10 Sieve Opening - Inches (Log Scale) U.S. Standard Sieves - ASTM Designation E 11-39 FIGURE 3. Bethel Soil 10 Aggregate Grading Chart Sieve No. Square Openings 270200 100 50 30 16 8 4 3/8" 3/4" 1-1/2" 3" 100 I I I I I I r I I ~I r .: : I-~ : 90 I I:::: : t= I : I=. :: 80 F I E~ / =:: ~ 70 ~ / ~ / ~ OJ ~ c I:: I = Vl 60 Vl E / ~ 0...'" l=- : ~ : c 50 E I Q) 1= : ...... ~ E I : --... Q) 0... t= : 40 E I ~ : '"0 g / I- - 1= / :: 30 : ~ / : E Sample No: #2-20 (#20) :: 20 = ~ Source: Bethel, Alaska =:: 1= Materials: Silty Sand - ~ :: 10 ~ ::: I I I I I I I I I I I \I I I I I I I II ~ 0 ~I I I I I I I I 0.001 0.01 0.1 Sieve Opening - Inches (Log Scale) U.S. Standard Sieves - ASTM Designation E 11-39 FIGURE 4. Bethel Soil 20 Aggregate Grading Chart LIQUID LIMIT (ASTM 0423-66), PLASTIC LIMIT AND PLASTICITY INDEX (ASTM 0424-59) OF SOLIDS The procedures used for these determinations are described in ASTM 0423-66 and 0424-59. Liquid limit and plastic limit data could not be obtained on Bethel Sample 1-10 due to loss of cohesion during specimen preparation. Sample 2-20 data is compiled in Tables 6 and 7. TABLE 6. Liquid Limit Bethel 2-20 No. of Hammer Sample Wt Wet Wt Dry LL Blows Wt (g) (g) (g) % H.O Average 12 49.19 59.41 57.72 19.18 49.54 59.11 57.53 19.77 19.29 25 49.30 59.05 57.56 18.07 49.29 57.34 56.04 19.26 18.65 35 49.96 60.96 59.26 18.28 51.88 58.33 57.34 18.13 18.21 TABLE 7. Plastic Limit Bethel 2-20 Beaker I~t Wet Wt Dry Plastic Wt (g) (g) (g) % H.O Limi t 48.71 50.29 50.03 19.70 51. 39 52.67 52.46 19.66 19.48 51.31 50.93 52.67 19.12 Plasticity Index = Liquid Limit - Plastic Limit. For Bethel 20 soil this is 18.7 - 19.5 = - 0.8. From ASTM 0 423-66, both Bethel 10 and 20 soils are categorized as nonplastic. Moisture Density Relationship (AASHTO T-180, ASTM 01557) This test is used to determine the maximum density at a given compactive effort and the water content at which it can be achieved. This test was conducted by both Battelle, Pacific Northwest Laboratories and University of Washington; the data is depicted in Figure 5 for Bethel 1-10 and 8-10 and Figure 6 for Bethel 2-20 and 10-20 samples. Differences in the-curves appear attributable tc differences in samples. 18 110r------~ o 0 Ib/ft3 o 100 Battelle Data 99 6 0 University of Washington Data 98 97 Maximum Density Water Content Ib/ft3 kg/m3 Volume % 96 0 108.1 1732 6.93 • 95 6 107.8 1726 6.2 94 o 2 4 6 8 10 12 14 16 18 20 22 24 % Water Content FIGURE 5. Moisture-Density Relation Bethel Soil 10 19 Ib/ft3 o Battelle Data D. University of Washington Data Maximum Density Water Content Ib/ft3 kg/m 3 Volume % o 108.7 1732 4.43 D. 112 1294 10.8 • o 2 4 6 8 10 12 14 16 18 20 22 % Water Content FIGURE 6. Moisture-Density Relation Bethel Soil 20 20 The Battelle data appears to show maximum density at 1m-fer water content for Bethel Soil 20 than the University of Washington data. ORGANIC CONTENT OF SOILS (ALASKA T-6) Using the Alaska T-6 procedure, organic content was determined for Bethel soils as tabulated in Table 8. TABLE 8. Organic Content of Bethel Soils (Alaska T-6) Bethel Cruc i b1 e Pre-Ignition Pos t-I gn it ion \olt. % Sample Wt (g) Dry Wt (g) Wt (g) Organic 1-10 17 .8173 30.2148 30.8738 1.16 17.6187 33.8884 33.7068 1.15 20.7643 31.6984 31.5693 1.19 2-20 17.4674 27.7337 27.6037 1.28 18.4204 31. 3060 31.1443 1. 27 20.1896 30.9029 30.7738 1.22 The organic content is very low, indicating no stability problems from degrading organic matter would be expected from either Bethel soil. Comparative Soil Characterization Data The only comparative characterization data available was from "Soil Stabilization for Remote Area Roads," by C. W. Gentry and D. C. Esch of State of Alaska OOT&PF which is yet unpublished. It is not known if the soil samples designated "Bethel clean" and "Bethel dirty" taken from Bethel Airport - Browns Slough Specific· Site MS-208-001-1 or MS-208-003-1 are the same sites (see Figure 2) for samples taken for this program (Table 9). 21 TABLE 9. Comparative Bethel Soil Characteristics, % Passing Designated Screens Sample #10 #30 #40 #50 #100 #200 #325 2-10 100 99 96 52 6 1 8-10 100 99 94 40 8 1-10 100 95 7 Bethel clean 100 99 96 41 9 4-20 100 98 69 20 4 2-20 100 99 62 29 10-20 100 95 7 Bethel dirty 100 98 59 20 22 ENGINEERING MEASUREMENTS, TEST SERIES 1 Two test series of engineering measurements were conducted by the subcontractor (University of Washington Civil Engineering Laboratory). Test Series 1 specimells were prepared by 1) using expected naturally-occurring moisture levels, and 2) visual judgment of soil particulate coating by the asphalt emulsion. One set of specimens was prepared using the maximum amount of each asphalt emulsion that the damp soil would hold, and one set of specimens at approximately 1% less asphalt. This resulted in test data in which emulsion intercomparison was not possible. In this test series emulsion and the Type 1 cement were added simultaneously. Test Series 2 specimens were prepared to allow intercomparison of both emulsion performance and effectiveness of cement addition. The arbitrarily-selected 8% by weight asphalt for Soil 10 and 9% by weight asphalt for Soil 20 could represent an excess of asphalt, which reduces the load-bearing capability from the optimum peak values. In Test Series 2 the Type 1 cement was mixed with the sand at least four hours prior to emulsion addition. The test procedures used by the subcontractor (University of Washington Civil Engineering Laboratory) Nere as follows: 1. Hveem-Stabilometer R-value (AASHTO T-90, ASTM 02844). 2. Resilient Modulus (Asphalt Institute Manual MS-I0). 3. California Bearing Ratio (ASTM 01883, AASHTO T-193-72). 4. Frost Heave Susceptibility Test (Alaska). The engineering measurements and soil classifications are approxi mately interrelated as shown in Figure 7. The California Bearing Ratio is utilized primarily in runway construction design in accordance with Federal Aviation Administration (FAA) guidelines. Hveem stability and cohesion is used primarily by the Western States for asphalt pavement design. The majority of the states use the Marshall compactor/stability measurement which is not directly correlatable to the Hveem-derived data. The resilient modulus measurement which is used to design the 23 California Bearing Ratio CBR 2 3 4 5 6 7 8 9 10 15 20 2"~ 30 40 50 60 70 80 90 100 UNIFIED ISOIL CL~SSIFldA TIO~ Corps of Engineers U.S. Army GP GW and GM U.S. Bureau of Reclamation GC SW SM SP SC OH ML OH CL OL MH I AASHO SOIL CLASSIFIC~ TIO~ , A I 9 Alb r I , A24 A25 , A"2"6" A27 A3 A4 A5 ([ I I A6 , A 7 5" A76 , ,I II , , , , i I 20 30 40, 50 55 60 70 80 88 Resistance Value R (Caldornia) ! I ! ! I, I i II 100 150 200, 250, 300, 400 500 600 700 80 o Modulus of Subgrade Reaction k psi per in I I ! , I ! i i 20 30, 40 50 1\ Bearing Value, psi 6r :30;in" ,D,ameter Pla.'e, 0" 1 '~" Dete,ction), I T General Soil Ratings as Subgrade, Subbase or Base Subgrade· Poor I Medium I Good I Excellent Subbase: Unacceptable I AcceptableT Good T Excellent Base: Accept able FIGURE 7. Approximate Interrelationship of Soil Classification and Bearing Values , required thickness is Quite sensitive to temperature. Resilient modulus, which has been advanced by the Asphalt Institute and other organizations, has not yet been accepted by the American Society for Testing ~aterials (ASTM) . PRELIMINARY MIX DESIGN The initial series of tests utilized soils of water content expected to be found naturally. In the preliminary mix designs the water content and residual asphalt content varied considerably with emulsion to provide Hveem specimens of similar quality. Visual judgment of particu late coverage by asphalt, specimen cohesiveness, liquidity, and color were used to select water and residual asphalt contents for test specimen preparation. A summary of these preliminary mix design observations appears in Table 10. TABLE 10. Preliminary Mix Design Visual Water Residual Evaluation Asphalt Content Aspha lt of Aggrega te So i 1 Emulsion (% ) (%) Coating 10 Chevron 10 8 fair CSS-1 10 9 good 8 8 very good 10 ARMAK 10 4.8 paste E4868 7 3.6 fair 7 4.2 very good 10 U.S. Oi 1 10 8 wet paste 504 8 7 paste 8 6 very good 20 Chevron 6 3.6 poor CSS-1 6 4.8 poor 6 6.0 good 6 6.6 paste 20 ARMAK 6 6 good E4868 6 4.8 good 6 4.2 poor 20 U.S. Oil 6 6 good 504 6 8 slight excess 6 7 very good 25 , Using the best mix designs, test specimens were prepared as shown in Table 1l. TABLE 11. Test Series 1, Specimen Preparation Matrix Aspha It Residual Cement Stabil ity Cohesion Resilient Emulsions Asphalt % Wt.% Specimens Specimens Modulus Soil 10 Chevron 6 0 3 3 CSS-1 6 0.5 3 3 6 1.0 3 3 6 2.0 3 3 * 8 0 3 3 8 0.5 3 3 8 1.0 3 3 * 8 2.0 3 3 1 Soil 20 10 0 3 3 10 0.5 3 3 10 1.0 3 3 10 2.0 3 3 9 0 3 3 9 0.5 3 3 9 1.0 3 3 9 2.0 3 3 U.S. Oil 5 0 3 3 504 5 0.5 3 3 5 1.0 3 3 5 2.0 3 3 6 0 3 3 6 0.5 3 3 6 1.0 3 3 6 2.0 3 3 1 Soil 20 8 0 3 3 8 0.5 3 3 8 1.0 3 3 8 2.0 3 3 1 9 0 3 3 9 0.5 3 3 9 1.0 3 3 9 2.0 3 3 26 TABLE 11. Test Series 1, Specimen Preparation Matrix (Continued) Aspha lt Residual Cement Stabil ity Cohesion Resilient Emulsion As~ha lt % Wt.% Specimens S~ecirnens Modulus ARMAK 3.2 0 3 3 E4868 3.2 0.5 3 3 3.2 1.0 3 ., 3.2 2.0 3 3" 4.2 0 3 3 4.2 0.5 3 3 4.2 1.0 3 3 4.2 2.0 3 3 1 Soil 20 6.0 0 3 3 6.0 0.5 3 3 6.0 1.0 3 3 6.0 2.0 3 3 7.0 0 3 3 7.0 0.5 3 3 7.0 1.0 3 3 7.0 2.0 3 3 35% Soil 10, 5.5 2.0 3 3 1 65% Soil 20 * CBR specimens prepared from this admixture. CALIFORNIA BEARING RATIO (CBR) (ASTM D1883, AASHTO T 193-72) The CBR test determines the load-bearing capacity of the structural layers involved in pavement, i.e., the natural subgrade material, the subbase course, or the base course. Results of this test are used to establish the course thickness, etc .. The test is one of penetration of a standard piston in which the force necessary to penetrate is expressed as a percentage of the force necessary to make the same penetration into crushed "Florida limerock." Crushed limestone has a CBR value of 80, for example. The CBR is very important in runway design, less so in highway design. The load-penetration curves obtained for Soil Samples 10 and 20 at various water contents are shown in Figures 8 and 9, respectively. Each curve was adjusted as required by the test method so that the curve passes through zero load. Relationship of CBR with compaction information is shown in Figure 10. The resultant CBR values are tabulated in Table 12. 27 800~------' 700 @ 9.3% Water Content 600 500 ~ "0 400 o --''" 300 200 O~----~----~~----~~--~~----~--~o 0.1 0.2 0.3 0.4 0.5 Penetration - inches FIGURE 8. Soil 10 CBR Load Penetration 28 800 CBR Soil 20 700 Water Content 600 500 ::9 "0 400 oC1l -' 300 @ 10% Water Content 200 100 oL-----~~----~------~------~------~----~00 0.1 0.2 0.3 0.4 0.5 Penetration, inches FIGURE 9. Soil 20 CBR Load Penetration • 29 10 cr: OJ U 5 O~--~-----L----~----~--~~--~----~----~--~ 115.------, ... ~ :i 110 u ~ £! ..; .r: OJ (j) 5: ,,= c :::> 105 2:- 0 100 o 5 10 15 20 Water Content, % FIGURE 10. CBR and Density Plotted vs. Water Content • 30 TABLE 12. California Bearing Ratio (Soaked, %) Untreated Water CBR % Soil Content % @ 0.1 " pen. @ 0.2" pen. 10 6.3 2.6 3.5 10 9.3 7.7 10.4 10 12.5 5.7 7.8 20 2.2 1.4 1.9 20 10.0 1.1 1.7 20 17.3 3.6 5.8 The U.S. Department of Transportation, Federal Aviation Administra tion guidelines for runway design requirements are contained in the Advisory Circular AC 150/5320-6C, "Airport Pavement Design and Evalua tion.,,(2) The basic runway design is based upon subbase, base and surface layers of thicknesses which are dependent upon 1) California Bearing Ratio (CBR) of subgrade material, 2) aircraft gross weight, and 3) number of annual departures. The subbase material CBR is 20 minimum; the base material CBR is 80 minimum as seen in Figure 7. Thickness reduction equivalency factors are allowed for specific materials which are known to exceed the above minimum CBR values. From FAA AC 150/5320-6C,(2) the recommended equivalency factor range for stabilized subbase is shown in Table 13; for stabilized base see Table 14. The factor range is proportionately dependent upon the CRR value of the subbase or base material. The Series 1 CBR test specimen composition was as follows: 1. Bethel Soil 10, 8% residual asphalt, Chevron CSS-l, 0% cement. 2. Bethel Soil 10, 8% residual asphalt, Chevron CSS-l, 2% cement. Single CBR specimens were prepared in the usual manner, but compacted using the 10-1b, 18-inch drop modified AASHTO procedure (6-inch diameter mold), cured for 48 hours at 140°F, cooled, soaked for 4 days in water, and then tested. 31 TABLE 13. Equivalency Factor* Range for Stabilized Subbase Material Equivalency Factor Range P-401, Bituminous Surface Course 1.7 - 2.3 P-201, Bituminous Base Course 1.7 - 2.3 P-215, Cold Laid Bituminous Base Course 1.5 - 1.7 P-216, Mixed-in-place Base Course 1.5-1.7 P-304, Cement-treated Base Course 1.6 - 2.3 P-301, Soil-cement Base Course 1.5 - 2.0 P-209, Crushed Aggregate Base Course 1.4 - 2.0 P-154, Subbase Course (CBR 20) 1.0 TABLE 14. Equivalency Factor** Range for Stabilized Base Material Equivalency Factor Range P-401, Bituminous Surface Course 1.2 - 1.6 P-201, Bituminous Base Course 1.2 - 1.6 P-215, Cold Laid Bituminous Base Course 1.0 - 1.2 P-216, Mixed-in-place Base Course 1.0 - 1.2 P-304, Cement Treated Base Course 1.2 - 1.6 P-301, Soil-Cement Base Course N/A P-154, Subbase Course N/A P-209, Crushed Aggregate Base Course (CBR 80) 1.0 * Equivalency factor when the following materials are substituted for subbase material of CBR 20. ** Equivalency factor when the following materials are substituted for base material of CBR 80. 32 The CBR test results at a.1-inch and a.2-inch penetration are shown in Table 15. TABLE 15. Test Series 1, CBR, Soil 10 Specimen CBR @ 0.1" pen @ 0.2" pen ( 1 ) 65% 57% (2 ) 73% 66% These CBR values from treated Soil 10 would allow use of this material as subbase material (minimum CBR 20), but would not allow its use as a base material (minimum CBR 80). The 0.1" penetration CBR value (0.1" penetration is usually the penetration used unless 0.2" penetration CBR is higher) is well in excess of 20 and, therefore, would be entitled to some thickness reduction equivalency factor. No Test Series 1 Soil 20 CBR tests were conducted because of the low values obtained with Soil 10. Test Series 2 CBR tests included both soils. In Test Series 2, CBR results with values well in excess of 100 allows maximum thickness reduction equivalency factors to be taken for both subbase and base courses. HVEEM STABILITY AND COHESION (AASHTO T-90) (ASTM 02844) Specimens were prepared from the proposed cold mix design method (see Appendix E) which is a modification of the Marshall Method, ASTM 01559-82. This procedure allows reaction between emulsion components and aggregate to take place during and after mixing. The material then is compacted at room temperature and after a 16 to 18 hour cure time is heated to 140°F for 48 hours, then compacted at 140°F, and then cooled for testing. This procedure is intended to duplicate cure and compaction conditions normally encountered in the field. Since Hveem stability and cohesion, resilient modulus MR, and CBR tests are all designed for hot mix specimen preparation, a change was necessary for cold mix emulsion applications . • 33 The R-value and CBR are approximately related as shown in Figure 7. The R-value is derived from the Hveem stability measurement by the relationship:* R = 100 - 100 [¥J [~ -lJ +1 where: Pv vertical pressure psi Ph horizontal pressure psi d displacement inches A total of 48 each Hveem stability and cohesion samples were prepared and tested. The four cement content ranges were arbitrarily chosen to include ranges one reasonably might use in the field. Cement content on a dry weight basis was 0, 0.5, 1.0, and 2.0%. The optimum asphalt content was established during preliminary mix design testing; the other asphalt content chosen was 1-2% by weight less than the optimum percentage. Stability and cohesion measurements as determined by the modified Marshall compaction sample preparation, California kneading compaction method (AASHTO T-190), and AASHTO T-246 testing method are tabulated in Tables 16 through 21. The effects of cement addition on the stability and cohesion properties of various asphalt emulsions-soil admixtures is depicted in Figure 11 for Bethel Soil 10, and Figure 12 for Bethel Soil 20. The cause of the "dip" observed in both stability and cohesion curves for Bethel Soil 10 in Figure 11 is speculative. As all ingredients (soil, cement, and emulsion) were essentially simultaneously added and mixed, possibly the cement, alkaline in nature, neutralized the normally stable-when-acid emulsion which caused the emulsion to degrade before maximum bonding was achieved. If so, this effect would be most pro nounced with the low asphalt concentration emulsion admixtures, which in general appears to be the case. At the higher asphalt emulsion concentra tions used with Bethel Soil 20, Figure 12, the dip is not general, *Additional informati~n on the R-value is found on pages 42 and 43. 34 TABLE 16. Summary of Test Data - U.S. Oil 504, Bethel Soil 10 Residual Specimen Bulk Air Average Aspha 1t Cement Height Densi ty Void Hveem Hveem R (wt. %) (wt.%) (in.) 1b/fP (%) Stabi 1 ity Average Cohesion Average Value 5 0 2.68 ll5.4 27.3 16.0 48.4 2.61 ll5.4 27.3 15.0 15.1 49.3 48.9 63.5 2.57 116.1 26.9 14.2 49.1 5 0.5 2.58 ll7.9 26.2 13.0 50.1 2.71 115.4 27.8 11.0 13.1 37.9 39.5 60.4 2.85 115.4 27.8 16.0 30.5 5 1.0 2.69 116.7 27.2 15.0 ll4;0 3.05 114.2 28.8 12.0 14.0 63.0 82.9 61.1 2.87 116.1 27.6 15.0 71.8 w U1 5 2.0 3.00 ll4.8 29.1 17 .0 86.8 3.03 115.4 28.7 21.0 18.5 78.5 90.8 70.3 2.71 ll6.1 28.4 17.5 107.2 6 0 2.90 115.4 22.9 21.0 277 .4 2.89 116.1 22.5 17.5 19.8 171.6 201.5 65.6 3.11 21.0 155.4 6 0.5 2.60 116.1 25.4 18.0 38.2 2.62 116.7 25.0 18.0 18.0 48.1 45.3 55.8 2.65 112.9 27.4 18.0 49.5 6 1.0 2.66 117.3 25.2 19.0 99.3 2.55 118.6 24.4 16.6 16.2 131.6 112.0 59.9 2.62 117.3 25.2 17.0 105.0 6 2.0 2.58 ll9.2 24.7 19.4 140.6 2.67 18.0 20.7 150.4 148.9 69.2 2.57 119.2 24.7 24.7 155.7 TABLE 17. Summary of Test Data - ARMAK E4868, Bethel Soil 10 Residual Specimen Bulk Air Average Asphalt Cement Height Density Void Hveem Hveem R (wt. %) (wt.%) ( in. ) lb/fP (%) Stability Average Cohesion Average Value 2.2 0 3.15 108.6 34.7 20.0 117.0 3.17 108.6 34.7 23.5 21.8 120.6 118.8 68.3 3.17 109.2 34.4 broken 3.2 0.5 2.94 1l0.5 32.4 22.0 63.0 2.84 23.5 22.8 62.3 69.8 67.8 2.99 117.9 27.8 84.3 3.2 1.0 2.60 109.2 33.6 17.0 21. 7 2.42 17.6 18.2 34.4 29.7 65.7 2.69 114.2 30.6 20.0 33.0 w m 3.2 2.0 2.47 23.2 43.6 2.47 20.0 21.8 54.8 51.5 73.3 2.47 114.2 31.1 22.2 56.1 4.2 0 3.06 113.6 38.6 30.0 232.2 2.94 113.6 28.6 23.0 25.3 190.8 196.8 70.9 3.11 111. 7 29.8 23.0 167.5 4.2 0.5 2.55 113.6 28.8 15.0 81.3 3.05 19.0 16.8 62.1 72.5 63.1 2.42 114.8 28.1 16.5 74.2 4.2 1.0 2.55 116.7 27.4 19.5 149.5 2.46 116.1 27.7 25.0 21.5 156.3 127.8 69.1 2.62 114.8 28.5 20.0 77 .5 4.2 2.0 2.95 21.0 148.8 2.58 114.8 29.1 18.0 19.8 146.5 140.8 69.9 2.95 114.2 29.5 20.5 127.2 • TABLE 18. Summary of Test Data - Chevron CSS-1, Bethel Soil 10 Residual Specimen Bulk Air Average Asphalt Cement Height Density Void Hveem Hveem R (wt. %) (wt. %) ( in. ) lb/fP (%) Stabil ity Average Cohesion Average Value 6 0 3.05 113.6 27.0 25.0 145.7 3.10 112.9 27.4 21.5 24.2 119.6 144.4 70.1 3.00 116.7 25.0 26.0 167.9 6 0.5 2.94 116.1 25.8 14.0 2.59 115.4 26.2 11.5 14.5 227.5 230.1 57.7 2.65 117.9 24.6 18.0 232.7 6 1.0 2.86 113.6 27.6 141.4 2.81 117.9 24.8 22.0 23.5 210.0 197.2 70.7 2.83 118.6 24.4 25.0 240.1 w ...... 6 2.0 2.47 119.2 24.7 26.0 226.9 2.85 116.7 26.3 20.0 23.3 55.5 116.7 72 .1 2.60 119.2 24.7 24.0 67.2 8 0 3.07 121.1 19.0 29.0 160.2 3.09 117.9 21.1 25.0 25.7 108.1 133.3 71.0 3.10 116.1 22.4 23.0 131.6 8 0.5 2.87 117.3 21.9 14.0 146.3 2.71 118.6 21.1 13.5 14.5 168.5 140.9 60.9 2.90 120.4 19.8 16.0 107.9 8 1.0 2.99 121. 7 19.2 19.0 307.2 3.10 119.9 20.9 20.0 19.3 268.0 254.3 63.2 2.88 121.1 19.6 19.0 177.7 8 2.0 2.88 121.1 20.3 21.5 244.2 3.05 121.1 20.3 24.0 21.5 278.9 271. 9 67.9 2.97 121.1 20.3 19.0 292.5 TABLE 19. Summary of Test Data - U.S. Oil 504, Bethel Soil 20 Residual Specimen Bul k Air Average Asphalt Cement Height Density Void Hveem Hveem R (wt.%) (wt. %) ( in. ) lb/ft3 (%) Stabil ity Average Cohesion Average Value 8 0 2.41 120.4 18.6 19.9 43.7 2.50 118.6 19.9 16.4 16.9 37.1 42.4 71.2 2.55 118.6 19.9 14.3 46.5 8 0.5 2.47 121.1 18.6 15.7 55.1 2.38 119.2 19.9 15.0 15.9 48.6 52.1 73.0 2.28 120.4 19.1 17.0 52.6 8 1.0 2.57 119.8 19.8 15.2 61.5 2.60 124.2 16.8 15.0 19.2 57.5 62.5 67.3 2.61 120.5 19.3 17.0 68.5 w 0::> 8 2.0 2.38 120.5 20.2 18.5 154.4 2.50 119.8 20.4 20.5 19.2 142.8 138.3 76.1 2.58 119.2 20.9 18.7 117.8 9 0 2.36 121.1 16.7 13.0 60.3 2.40 119.8 17.5 16.5 15.9 37.3 54.1 70.2 2.44 121.1 16.7 18.1 64.7 9 0.5 2.30 121.1 17.2 13.5 56.3 2.38 121. 7 16.7 13.5 15.0 58.6 60.9 69.2 2.20 122.3 16.3 18.0 67.8 9 1.0 2.48 120.4 17.8 12.0 60.7 2.26 121. 7 16.9 17 .0 15.3 59.5 63.0 70.5 2.26 121. 7 16.9 17.0 68.7 9 2.0 2.29 122.3 17.2 19.0 116.9 2.50 121. 7 17.6 18.2 17.1 114.2 108.6 74.0 2.31 121.1 18.1 14.0 94.7 TABLE 20. Summary of Test Data - ARMAK E4868, Bethel Soil 20 Residual Specimen Bulk Air Average Aspha It Cement Height Density Void Hveem Hveem R (wt.%) (wt. %) ( in. ) 1 b/fP (%) Stability Average Cohesion Average Value 6.0 0 2.25 117.3 23.9 19.5 104.4 2.40 116.7 24.3 12.9 16.5 100.2 94.9 69.1 2.46 116.1 24.7 17.0 80.1 6.0 0.5 2.41 114.8 25.8 18.2 71.5 2.30 115.4 25.4 16.0 15.9 69.6 69.4 69.0 2.49 114.8 25.8 13.6 67.1 6.0 1.0 2.61 115.4 25.9 14.0 59.9 2.39 116.1 25.5 13.5 15.4 70.3 69.4 69.7 2.46 116.1 25.5 18.6 78.1 6.0 2.0 2.40 116.7 25.5 23.0 151. 7 2.41 117.3 25.1 25.0 24.0 w 150.7 154.3 80.6 <.0 2.22 117.3 25.1 24.0 160.4 7.0 0 2.52 118.6 21.5 18.0 62.5 2.45 118.6 21.5 16.9 17.3 73.3 70.5 72.7 2.27 118.6 21.5 17.0 75.7 7.0 0.5 2.34 117.9 22.2 15.0 49.4 2.31 118.6 21.8 17.0 15.7 62.4 53.8 74.9 2.31 117.9 22.2 15.0 49.5 7.0 1.0 2.31 118.6 22.2 17.0 66.4 2.32 116.7 23.4 14.0 15.0 64.2 64.5 74.0 2.17 118.6 22.2 14.0 62.8 7.0 2.0 2.17 118.6 22.7 18.5 164.1 2.27 117.3 23.5 19.0 19.2 143.6 145.1 80.4 2.18 117.9 23.1 20.0 127.5 Soil Blend: 35% Bethel 10, 65% Bethel 20 5.5 2.0 2.37 116.1 26.4 20.0 20.6 103.8 2.40 116.7 26.0 21.1 133.2 118.5 78.9 TABLE 21. Summary of Test Data - Chevron CSS-l, Bethel Soil 20 Residual Specimen Bulk Air Average Asphalt Cement Height Density Void Hveem Hveem R (wt. %) (wt. %) ( in. ) 1b/fP (%) Stabil ity Average Cohesion Average Value 10 0 1.87 121.1 15.2 8.5 71.5 2.37 121.1 15.2 14.0 12.5 57.9 63.2 73.4 2.29 122.3 14.3 15.0 60.3 10 0.5 2.23 121. 7 15.0 12.5 68.8 2.23 121. 7 15.0 15.0 13.7 59.0 60.5 70.0 2.54 119.2 16.7 13.5 53.7 10 1.0 2.55 120.4 16.3 14.9 59.0 2.69 120.4 16.3 16.0 14.5 57.8 57.7 66.4 2.62 119.8 16.7 12.5 56.3 a~ 10 2.0 2.69 18.0 134.9 2.25 122.3 15.7 19.5 19.3 111.5 104.5 74.1 2.41 121.1 16.5 20.3 67.1 9 0 2.45 119:8 17 .5 17.4 52.4 2.63 119.8 17.5 18.0 17.5 68.9 61.7 69.6 2.63 119.2 18.0 17 .0 63.8 9 0.5 2.66 119.2 18.4 14.0 51.6 2.48 121.1 17 .2 17.2 15.9 67.5 58.9 66.8 2.40 119.8 18.0 18.0 57.6 9 1.0 2.51 120.4 17.8 18.5 69.6 2.48 120.4 17 .8 18.5 17 . 5 56.1 64.9 67.8 2.48 120.4 17.8 15.6 69.1 9 2.0 2.45 121.1 18.1 21.8 96.8 2.43 120.4 18.5 17 .8 20.2 91.5 87.6 75.6 2.45 120.4 18.5 21.1 74.6 Asphalt, Weight % Asphalt Symbol Type Soil 10 0 Chevron 8.0 Chevron 6.0 6• Armak 4.2 A Armak 2,2, 3.2 0 U.S. Oil 6.0 300 • U.S. Oil 5.0 250 200 c '2 '" L:'" o 150 u E '"> I'" > .::l ~ 10L-L-______L- ______~ ______~ ______L ____ ~ o 0.5 1.0 1.5 2.0 Cement, % FIGURE 11. Test Series 1 S.tabil ity and Cohesion - Soil 10 41 160 Asphalt. Weight % Asphalt Symbol Type Soil 20 0 Chevron 10.0 140 Chevron 9.0 •6. Armak 7.0 Armak 6.0 •0 U.S. Oil 9.0 120 • U.S. Oil 8.0 c g UJ Q) .c 0 100 u E Q) Q) > I -- 80 60 > 20 40 -" ro Ui E Q) Q) > I 15 10~ ______J- ______~ ______L- ______-L ____ ~ o 0.5 1.0 1.5 2.0 Cement, % FIGURE 12. Test Series 1 Stability and Cohesion - Soil 20 42 lending some credence to the neutralization theory. In addition, insufficient reaction time between cement and soil or inadequate mixing could lead to the cement becoming an alkalinity source rather than coating and forming silicate bonds to the soil aggregates. This would result in weaker bond formation, and the emulsion would wash the cement off the sand, which results in lower compaction strengths. It should also be noted that a cationic asphalt emulsion would be more unstable at high pH conditions and the competitive calcium cations from cement dissolution would compete for the anionic deposition sites on the aggregate. This situation"would occur with simultaneous addition and mixing. This appears to be the case for ARMAK E4868 emulsion with both Bethel soils, but is most apparent in the cohesion measurements of the Bethel Soil 20 admixtures (see Figure 12). This dip has not been observed in test data in other programs. Neither AKZO Chemie America or University of Washington Civil Engineering Department personnel had previously encountered this situation. They attributed the phenomenon to chemical interaction. The extent to which soil specimens were compromised in stability and cohesion strengths is not known. The overall effect, if deleterious, is manageable in terms of observed physical properties of the treated soil. Stability measurements obtained from specimens of various thick nesses is converted to a "resistance value" known as R-value. The R-value is used in highway design to determine support capability. R-values vary from state to state somewhat, but a California (Hveem) R-value was what was determined in this program in accordance with AASHTO T-190-78 or ASTM 02844-69. The R-value relationship to soil classification and soil-bearing values is illustrated in Figure 7. Alaska Test Method T-24 uses the R-value to determine gravel thickness requirements over the subgrade soil to prevent plastic deformation as shown in Figure 13. R-values are used to determine support strength of subgrade, subbase, and base course materials. A dotted line on Figures 11 and 12 represents an R-value of 70 equivalency which is typical of a good quality pit-run gravel subbase material. 43 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 III 1.8 ::l row 2.0 > III Bro 22 c U CO(/) 2.4 .... (j) 'u; 2.6 III 1.4 (/) 2.8 1;;;,0_.. 0: Q) 1.2 0- 3.0 1.0 /~ 3.2 0.8/ C1l 3.4 0.6 3.6 3.8 4.0 4.2 4.4 Example: Subgrade R-Value 31 Traffic Index (Til 8.0 Gravel Equivalent Factor (Gf) 1.5 The thickness of gravel required to prevent plastic deformation of the soil tested is 1.2-inches when corrected for the slab value of the upper layers of cover material. FIGURE 13. Design Chart for Thickness of Layers of Pavement Structure 44 RESILIENT MODULUS (M R) The resilient modulus is a measurement to establish approximate pavement structure thickness requirements. The resilient modulus of the subgrade soil is measured under various loads and confining stresses by a method being developed by ASTM, but not yet adopted by the Federal Aviation Administration. Consequently, thickness determination of stabilized subgrade soil will be based upon highway applications, not airfield related experience. The relationship of resilient modulus of subgrade material to soil classification and bearing values is shown in Figure 7. A CBR measure ment of subgrade which is relatively easy to obtain in the field will provide an approximate resilient modulus correlation from Figure 7. All resilient modulus specimens were prepared as were those for the Hveem stabilometer and cohesiometer measurements. After mixing and transfer to the test mold, specimen and mold were cured at 140°F in a recirculating oven as described in Appendix E. All resilient modulus measurements were conducted on 73°F specimens as required. This measurement is known to be temperature sensitive, because asphalts are temperature sensitive. The design mixes selected for resilient modulus testing all con tained 2% cement and represented the maximum stability and cohesion strengths obtained with design mixes involving all three emulsions. Three or four resilient modulus MR specimens were prepared for each of the above mixes. One specimen was expended on the cured resilient modulus measurement, the remnants were then extracted to determine the true asphalt content. Another specimen was evacuated, backfilled with distilled water, covered with water for 24 hours, followed by freezing at OaF for 6 hours, and thawing to room temperature. The resilient modulus was then determined. Table 22 lists the specimens prepared for resilient modulus, MR, testing. The test method followed closely the guidelines provided by a tentative ASTM method. Repeated loading is applied across the vertical diameter of the specimen. Three loadings, 25, 50, and 100 lb, were applied for 0.1 second~ followed by a 2.9 second relaxation period, and 45 TABLE 22. Specimens for Resilient Modulus, MR Residual Asphalt Cement Soil Emulsion (% ) (~0 ) 10 U.S. Oil 504 6.0 2.0 10 Chevron 8.0 2.0 10 ARMAK E4868 4.2 2.0 20 U.S. Oil 504 8.0 2.0 20 Chevron CSS-1 9.0 2.0 20 ARMAK E4868 6.0 2.0 Blend* ARMAK E4868 5.5 2.0 *35% Bethel 10 soil, 65% Bethel 20 soil . the process is repeated up to 20 cycles per minute. At least 100 cycles passed before resilient deformation was recorded so that reasonably uniform response could be assured. Resilient modulus, MR, is computed from: M = P(~ + 0.2734) R t(l'lh) where: P = applied load, lb ~ = Poissons ratio (constant 0.35) t = specimen thickness, inches I'lh = resilient deformation, inches Results of the resilient modulus measurements are compiled in Table 23 for Bethel Soil 10 and Table 24 for Bethel Soil 20, respectively. 46 TABLE 23. Summary of Resilient Modulus Tests for Bethel Soil 10 2% Cement Content Nominal Actual Air Applied Resilient Modulus (psi x 10 3 ) Aspha lt Asphalt Height Density Voids Load Dry Soaked*, F&T Emulsion (%) (%) ( in. ) lbs/fP (%) (1 b) Ind Avg Ind Avg Chevron 8.0 7.5 2.39 121.1 20.3 25 483 525 1088 795 CSS-l 567 502 50 362 318 372 368 335 327 100 261 269 249 248 ..,. 277 246 " Armak 4.5 3.9 2.57 114.8 29.1 25 505 607 E4868 505 505 552 580 50 368 289 311 339 282 286 100 292 211 258 275 229 220 U.S. Oil 6.0 5.5 2.45 118.6 25.1 25 530 637 504 471 500 579 608 50 274 327 326 300 296 213 100 271 271 255 248 271 240 * Soaked in water, frozen, thawed. TABLE 24. Summary of Resilient Modulus Tests for Bethel Soil 20 & Blend 2% Cement Content Nominal Actual Air Applied Resilient Modulus (psi x 10 3 ) Asphalt Asphalt Height Dens ity Voids Load Dry Soaked*, F&T Emulsion (%) (%) ( in. ) 1bs/fP (%) (1 b) Ind Avg Ind Avg 17.6 Chevron 9.0 7.8 2.24 121. 7 25 696 605 871 1016 CSS-1 515 1160 50 376 464 381 378 464 464 100 371 381 327 349 357 369 Armak 6.0 5.0 2.31 117.3 25.1 25 613 681 1039 942 E4868 750 844 50 500 409 ..,. 500 500 409 409 co 346 100 397 397 338 397 329 U.S. Oil 8.0 7.1 2.28 120.4 20.0 25 455 622 504 488 471 684 653 50 351 342 333 342 318 330 100 322 279 322 322 258 269 Armak** 5.5 5.2 2.35 116.1 26.4 25 1105 1026 1474 14m E4868 947 1328 50 1326 577 577 951 553 565 100 663 409 558 610 390 400 * Soaked in water, frozen, thawed. **Blend - 35% Bethel Soil 10, 65% Bethel Soil 20. The single soak-freeze-thaw cycle did not appear to physically affect any of the specimens. The specimens exhibited increased MR at the lower applied loads but decreased somewhat at the higher loads. This may be related to: 1. The soak-freeze-thaw specimens had more time to cure - about 9 days longer. 2. With 2% cement content, additional time enabled additional cement cure. 3. Specimen saturation with water adds significantly to the modulus at the lower applied loads, but detracts at higher loads. The soak-freeze-thaw test to denote effects on specimen resilient modulus was not intended to replace the State of Alaska DOT&PF developed frost heave test. The information derived from the soak-freeze-thaw using pre- and post-resilient modulus measurements is indicative only. The zero dimensional change observed in the frozen specimens involved oven-cured specimens. It is debatable if this represents typical field condition curing; however, oven curing is part of the ASTM specimen preparation procedure involved in stability and cohesiveness measurements. 49 ENGINEERING MEASUREMENTS, TEST SERIES 2* After the initial test series it became apparent from CBR test results that Bethel soil admixtures could only be utilized in subbase ~ Z , ' applications in runway construction. In addition, R-values averaged .) somewhat below those of a quality subbase material for highway construc- tion. A mix design change was needed to ~\'Ie_r the soil water content and increase the asphalt content. There was also a need for comparative engineering data from test specimens prepared from identical soil, cement, and asphalt content. The sequence of preparation of specimens in Test Series 2 was similar to Test Series 1 except that Portland cement was mixed with the damp soil and stored 15 hours in plastic bags prior to mixing with the emulsion. Cement content was reduced to 1.5% by weight maximum, primarily because of anticipated stiffness of the 15 hour old admixture if 2% was used. This proved to be no problem; in fact, cement content could probably be as high as 2.5% by weight before mechanical breakup would be requ ired. PRELIMINARY DESIGN MIX Moisture-density tests were conducted on admixtures in which about 4% soil water provided good mixing and coating yet supplied adequate moisture for cement hydration as shown in Figure 14. Two moisture-density tests were conducted on each soil containing 1.5 wt.% cement to indicate that the maximum dry density occurs at or near the same water content as the soil alone, also shown in Figure 14. The use of _~~__ soil moisture resulted in ARMAK E4868 and U.S. Oil 504 mixtures that were too wet for compaction. Mix designs for the second series are tabulated in Table 25. * For the relationship of Test Series 2 Engineering Measurements to those of Test Series 1, refer to the introductory remarks, p.23. 50 120.------~ _.--...... With 1.5 % Cement ....; Soil 10 115 -U ..0 -;. 105 100~~ ____~~ ____~ ______~ ______~ ______~ ______~ 120~------~ Soil 20 -u 115 ..0 > 105~~----~~----~------~------~------~------~ o 2 4 6 8 10 Mixing Water Added, % FIGURE 14. Test Series 2 Moisture-Density Relationships 51 I The reduction of water content of Alaskan Delta sands below natural levels may be accomplished by drum-dryer operation. This may be \/~equired in order to incorporate sufficient asphalt binder to achieve high support strength required of subbase and base materials for minimal surface course thickness. For Bethel Soil 10, a residual asphalt content of 8% by weight was arbitrarily chosen and soil water adjusted by drying as required. A 9% residual asphalt \'las chosen for Bethel Soil 20 and soil water was adjusted by drying. TABLE 25. Test Series 2 Mix Designs Asphalt Water Residual Visual Soil Emulsion Content % Asphalt Evaluation 10 Chevron 2 8 poor mixing CSS-l 4 8 good coating 10 ARMAK 4 8 poor E4868 2 8 too wet 1 8 good coating 10 U.S. Oil 4 8 too wet 504 2 8 good 20 Chevron 4 9 good CSS-l 20 ARMAK 2 9 too wet E4868 1 good 20 U.S. Oil 2 9 too dry 504 4 9 good Using the design mixes judged best by appearance, a total of 134 specimens were prepared for stability, cohesion, resilient modulus (M R), frost heave, and CBR tests as a function of cement content as shown in matrix form in Table 26. 52 TABLE 26. Test Series 2 Specimen Preparation Matrix Asphalt Residual Cement Stabil ity Cohesion Res il i ent Frost Emulsion Aseha lt % wt.% Specimens Specimens Modulus Heave Soil 10 Chevron 8 0 3 3 1 CSS-l 8 0.75 3 3 1 * 8 1.5 3 3 1 1 ARMAK 8 0 3 3 1 E4868 8 0.75 3 3 1 8 1.5 3 3 1 1 U.S. Oil 8 0 3 3 1 504 8 0.75 3 3 1 8 1.5 3 3 1 1 Soil 20 Chevron 9 0 3 3 1 CSS-l 9 0.75 3 3 1 * 9 1.5 3 3 1 1 ARMAK 9 0 3 3 1 E4868 9 0.75 3 3 1 9 1.5 3 3 1 1 U.S. Oil 9 0 3 3 1 504 9 0.75 3 3 1 9 1.5 3 3 1 1 *CBR specimens prepared from this admixture. CALIFORNIA BEARING RATIO Two specimens prepared as in the initial test series except 5 hour contact of cement with soil was allowed (see Appendix E) were tested in accordance with ASTM 01883-73. 53 TEST SERIES 2 CBR SPECIMEN COMPOSITION 1. Bethel Soil 10, 8% (residual) Chevron CSS-1 Emulsion, 1.5% Cement 2. Bethel Soil 20, 9% (residual) Chevron CSS-1 Emulsion, 1.5% Cement The test results are tabulated in Table 27. TABLE 27. CBR Results, Test Series 2 1. CBR @ 0.1" pen. = 113% CBR @ 0.2" pen. = 107% 2. CBR @ 0.1" pen. = 165% CBR @ 0.2" pen. = 138% The high CBR values exceeded expectations and show that the speci mens qualify as base course materials of a quality exceeding crushed limestone. The upper limit for usable CBR values is 100, which will qualify for a 20% thickness reduction of surface coat thickness which further reduces the gravel import requirements.(3) Using a base course material with a CBR of 100 for subbase and base courses allows thickness reduction factors as listed in Tables 14 and 15. A sample calculation using these CBR values is presented later in the Summary and Conclusions Section. ~veem Stability and Cohesion A series of nine each Hveem stability and cohesion specimens were prepared for each soil type tested. These specimens were prepared by methods similar to Test Series 1 specimens except for the 15 hour allowance of cement-damp soil contact time before emulsion addition. Specimen curing and compacting were according to "Modification of the Marshall Method ASTM D-1559-82," except the Hveem kneading compactor was used in place of the Marshall hammer. The Hveem stability and cohesion data as a function of cement content from Series 2 tests is tabulated in Table 28 and depicted graphically in Figure 15 for Soil 10 and Figure 16 for Soil 20. 54 TABLE 28. Test Series 2 Hveem Stabil ity and Cohesion Test Data Specimen Bulk Stability Cohesion Asphalt Asphalt Cement Height Unit Wt. Air Voids Emulsion (°'0 ) (001 lin.! (Ib eu ftl (Cl'Q) Ind. Avg. Ind. Avg. R-VaJue Chevron BO 0 119.2 lB.l 16.0 17.5 35.3 363 69.5 C551 19.0 37.3 (new) 8.0 0.75 120A 17 A 19.0 16.0 54.4 55.3 68.0 14"0 H O) 2 13.0 56.2 8.0 1 50 122.9 16.3 16.0 18.0 88A 92.2 71 5 20.0 96.1 Armak 8.0 0 119.8 15.3 16.5 17.0 67.6 60.6 68.5 C551 17.5 53.6 (new) 8.0 0.75 120A 15.5 15.0 16.3 68.2 65.7 69.0 11"0 H O) 2 17.5 63.2 8.0 1.50 119.8 16.5 20.0 18.5 96.6 90.7 72.3 17.0 84.7 U.5. Oil 8.0 0 120A 15.8 18.0 15.5 55.9 52.5 64.5 CSSl 13.0 49.2 (new) 121.7 17.3 17.9 12',6 H O) 8.0 0.75 15.5 58.3 60.9 68.5 2 18.5 53.5 8.0 1.50 121 1 16.2 19.5 20.5 84.8 87.9 71.5 21.5 91.0 Chevron 9.0 0 120.4 16.0 17.5 16.8 56.3 56.1 68.8 C5S1 16.8 55.8 (new) 9.0 0.75 121 7 15.7 14.5 15.3 58.7 68.0 69.0 14°/0 H O) 2 16.0 77.2 9.0 1 50 122.3 158 16.5 18.3 94.7 93.7 71.0 20.8 92.6 Armak 9.0 0 120A 13.9 19.0 18.5 84.5 83A 68.8 C55 1 18.0 82.2 (new) 9.0 0.75 121 .7 13.8 18.5 18.5 86.2 80.2 69.5 11°'0 H O) 2 18.5 74.2 9.0 1 50 121 .7 14.2 18.5 20.1 92.8 91.5 72.8 21.6 90.2 U.S. Oil 9.0 0 121.7 15A 14.5 15.0 83.6 79.8 65.5 CSSl 15.5 76.0 (new) 9.0 075 122.3 15.5 18.0 16.8 56.2 65.8 72.5 14°0 H O) 2 15.5 75A 9.0 1 50 122.3 15.9 19.5 17.8 88.1 89.9 69.0 16.0 91.6 • 55 Symbol 8% Asphalt Soil 10 0 Chevron 100 /:). Armak 0 U.S. Oil 75 c • 0 V) .cCLl 0 u /:).- E CLl CLl > 50 I >- 20 25 .~ -" • (j)'""'" E CLl CLl > I 15 10 o 0.5 1.0 1.5 2.0 Cement, % FIGURE 15. Test Series 2 Stability and Cohesion - Soil 10 • 56 Symbol 9% Asphalt Soil 20 0 Chevron 6. Armak 100 0 U.S. Oil 75 c 30 0 en <1l .s:: 0 U E <1l <1l :c> 25 50 > 20 25 .~ .Q en+"'" E <1l <1l > ~~~~------:c 15 10 o 0.5 1.0 1.5 2.0 Cement, % FIGURE 16. Test Series 2 Stability and Cohesion - Soil 20 57 From Figures 15 and 16, the stability is only slightly improved with increasing cement addition. The stability decrease observed previously at 0.5% cement, Soil 10 (Figure 8), is apparent at 0.75% cement, but is less pronounced. The improvement is attributed to sufficient cement-aggregate bonding time prior to emulsion addition. Cohesion increases directly with cement content. R-values from Table 28 at 0% cement averaged 67.5 for Soil 10, 67.7 for Soil 20, and increased at 1.5% cement to 71.8 for Soil 10 and 70.9 for Soil 20. These latter values correspond to a moderately-good pit-run gravel. In general, R-values were slightly higher than Test Series 1 specimens which contained considerably less asphalt. A line which approximates an R-value of 70 appears on both Figures 15 and 16. RESILIENT MODULUS (MR) SERIES 2 The design mixes selected for Series 2 resilient modulus (MR) tests all contained 1.5% cement and 8% residual asphalt in Soil 10 specimen, 9% residual asphalt in Soil 20 specimens. The resilient modulus (M R) specimens were prepared as were those for the Hveem stability and cohesion measurements. After mixing and transfer to the test mold, the specimens were cured at 140°F in a recir culating oven as described in Appendix E. Curing time of Series 2 test specimens was 5 hours longer than that of the initial series. This would not be expected to have any significant effect on the test data. All resilient modulus (M R) tests were conducted at 73°F as previously conducted. Results of the resilient modulus measurements are compiled in Table 29 for Bethel Soil 10 and Table 30 for Bethel Soil 20, respectively. MR values obtained from the initial test series for both soils are also tabulated in Tables 29 and 30 for comparison purposes. For Soil 10, the MR values from both test series are similar in spite of considerable asphalt and cement content differences. The Soil 20 MR values from Test Series 1 appear to be dominated by the additional 0.5% higher cement content than Series 2 specimens. 58 TABLE 29. Resilient Modulus Test Data, Soil 10 Test Series 1 Test Series 2 Emulsion ---Load 1b Asphalt % Cement % ~~ ~~ Cement % Asphalt % Chevron 25 8.0 2.0 525 492 1.5 8.0 CSS-l '50 368 336 100 269 252 ARMAK 25 4.5 2.0 505 312 1.5 8.0 E4868 50 339 287 100 275 237 U.S. Oil 25 6.0 2.0 500 483 1.5 8.0 504 50 300 407 100 271 302 TABLE 30. Resilient Modulus Test Data, Soil 20 Test Series 1 Test Series 2 Emulsion Load lb Aspha lt % Cement % ~ ksi ~ ksi Cement % Asphalt :,; Chevron 25 9.0 2.0 605 237 1.5 9.0 CSS-1 50 378 164 100 349 129 ARMAK 25 6.0 2.0 681 385 1.5 9.0 E4868 50 500 252 100 397 204 U.S. Oil 25 8.0 2.0 471 400 1.5 9.0 504 50 342 240 100 322 181 • 59 FROST HEAVE SUSCEPTIBILITY TESTS A unidirectional frost heave test was conducted on single specimens prepared from admixtures \~hich demonstrated high Hveem stability and cohesion. The frost heave specimen identification and composition as excerpted from Table 26 for reader convenience is tabulated below: TABLE 31. Frost Heave Specimen Composition Aspha lt % Residual* Emulsion Asphalt % Cement* So ill 0 Chevron 8 1.5 CSS-1 ARMAK 8 1.5 E4868 U.S. Oil 8 1.5 504 Soil 20 Chevron 9 1.5 CSS-1 ARMAK 9 1.5 E4868 U.S. Oil 9 1.5 504 * % by weight (dry basis). Specimens were prepared from the previous admixtures with the proposed modified Marshall Method, ASTM D-1559-82 described in Appendix E. The compacted specimens in molds were tested for frost heave susceptibility in a modified freezer according to a procedure furnished by the State of Alaska Department of Transportation and Public Facilities (see Appendix F). Approximately the same freezing rates were obtained in the Battelle modified freezer as reported by Gentry and Esch.(l) 60 Test Results No specimen expansion was measured during the 72-hour exposure. A 0.005 to 0.007-inch contraction was measured during the 72-hour exposure for each of the six specimens and the 46-inch extension rod. The inability to measure frost heave during exposure of the stabilized Bethel soil specimens was considerably different from a previous investigation involving Bethel soil.(1) One explanation may be that there was lower water absorption during the 16-hour minimum water immersion prior to frost heave testing. When no freeze-expansion was noted, the specimens were removed from the test apparatus and removed from the mold in frozen condition and thawed in plastic bags. After weighing, the specimens were placed in a room-temperature dessicator with reduced pressure capability. After 24 hours at reduced pressure the specimens were returned to ambient pressure and reweighed. Only those specimens that could be extruded from the mold were used in this test. The recorded test data is given in Table 32. TABLE 32. Frost Heave Specimen Water Content 01 % Pre Post Water 10 Specimen Aspha It Weight, g Weight, g Removed, g Water So i 1 10 Chevron 8 995.8 986.7 9.1 0.9 CSS-1 ARMAK 8 Specimen Shattered E4868 • U.S. Oil 8 947.7 945.3 2.4 o• ..>') 504 Soil 20 Chevron 9 Specimen Shattered CSS-1 ARMAK 9 969.0 967.3 1.7 0.2 E4868 U.S. Oil 9 902.8 902.9 0 0 504 61 From Table 32 it is apparent the frost heave test specimen moisture levels (pretest/sorption during test) were found to be < 1% by weight. The manner in which the frost heave test was conducted (see Appendix F) precludes significant drying during test exposure. The test specimens were apparently incapable of sufficient moisture uptake to produce a measurable frost heave. Gentry and Esch(l) reported frost heave for unstabilized samples of about 0.6-in. for "Bethel dirty" and about 0.3-in. for "Bethel clean" soil specimens after 72 hours of exposure. These specimens, prepared from soils characteristically similar to the Bethel 10 and Bethel 20 soils of this program, contained a minimum of 10% water. The Bethel 10 and Bethel 20 soil specimens proved highly resistant to frost heave. The soils are clearly superior to most soil materials in this respect, certainly those available in the Yukon-Kuskokwim Delta areas. • 62 SU~IMARY AND CONCLUS IONS The following conclusions may be drawn from the experimental data from this program. CHARACTERIZATION The size distribution data from the two Bethel soils for this program is very similar to the "Bethel clean" and "Bethel dirty" soil samples described previously by Gentry and Esch.(I) The zeta potential and surface area measurements of both Bethel soils signify a low zeta cationic asphalt emulsion vlill be required to achieve a high percentage of aggregate coating. ARMAK E4868, a cationic asphalt emulsion of about + 18 mv zeta potential was selected for the 26-34 zeta potential soils and 1.7 to 12.4 m2/g surface area, respectively. The specific gravities of the Bethel soil samples are reasonably close to those of the "Bethel clean" and "Bethel dirty" samples reported by Gentry and Esch as shown in Table 33. TABLE 33. Comparative Soil Specific Gravity S~ecific Gravity g/cc Sam~le Battelle ARMAK DOT&PF 10 2.69 2.70 20 2.72 2.70 Bethel clean* 2.67 Bethel dirty* 2.67 *Gentry and Esch. (1) The moisture-density relationship for the two Bethel soils in this program compared to those reported by Gentry and Esch(1) are shown in Table 34 . • 63 TABLE 34. Modified Proctor Density Soil Maximum Proctor Density Water Content Sample 1b/ft3 Volume % 10* 108.1 6.9 10** 107.8 6.2 Bethel clean*** 110.5 13.4 20* 108.1 4.4 20** 112.0 10.8 Bethel di rty*** 112.8 13.0 * Battelle Data. ** University of Washington Data. ***Gentry and Esch. (1) From Table 34, the data shows the variance in soil sample modified proctor density as measured by three laboratories. Although data spread is significant it is not unusual and may be due in part to sample nonhomogeneity. This may be of concern if this soil source is to be / utilized in compacted fills. Comparisons of particle size distribution of the Bethel soils of this program with those reported by Gentry and Esch(l) are tabulated in Table 35 using only common sieve sizes. The reader is referred to Table 9 for total size distribution. TABLE 35. Particle Size Distribution of Bethel Soils SamEle % Passing Sieve Size 10 40 50 100 200 Bethel 10* 100 99 96 52 6 Bethe 1 10** 99 94 40 8 Bethel clean*** 100 99 96 41 9 Bethel 20* 100 98 69 20 Bethel 20** 100 99 62 26 Bethel di rty*** 100 98 59 20 * AKZO Chemie America Data. ** University of Washington Data. ***Gentry and Esch. (1) 64 Reasonably good agreement on particle size distribution was found. Under the unified soil classification system, Bethel 10 and "Bethel clean" would be classified as poorly graded sand; Bethel 20 and "Bethel dirty" would be classified as silty sand. According to FM Advisory Circular, "Airport Pavement and Design and Evaluation,,,(2) the value of these soils as a base directly under the wearing surface of a runway is poor to unsuitable. These untreated soils are rated as poor or unacceptable as subbase and base course materials for highway applications as shown in Figure 7. Portland cement or bituminous stabilization agents are recommended. Nonorganic typical sands from the Yukon and Kuskokwin Delta areas 7 containing as much as 26% silt may be successfully stabilized, after coating with Type 1 cement, using CSS-1 asphalt emulsion for use as subbase and base layers beneath a pavement. ENGINEERING MEASUREMENTS AND COST ANALYSIS California Bearing Ratio (CBR) From FAA AC 150/5320,(2) hypothetical runway design configurations can be postulated using the CBR data obtained previously on Bethel soils and assuming aircraft gross weight and departure frequency. From Table 12, applying CBR values of 10 for Soil 10 and 4 for Soil 20 to Figure 17 of FAA AC 150/5320 for total pavement thickness, requirements for 150,000 lb gross weight aircraft (Hercules 130) and 1200 annual departures translates into the course thickness in Table 36 using crushed aggregate. • TABLE 36. Pavement Course Thickness Requirements (Crushed Aggregate) Soil Subgrade Surface Base Course Subbase Tota 1 Pavement Type CBR Course (in.) ( in. ) Course (in.) Thickness (in.) 10 10 4 12.5 8.5 21 20 4 4 12.5 24.5 37 Assuming a runway 4000-feet long and 100-feet wide and a subbase upgrade equivalency of 2 for crushed aggregate, a total of 28,880 yd3 would be needed over Subgrade Soil 10 and 29,300 yd3 for Subgrade Soil 20. 65 CBR 3 15 20 30 40 50 Note: Curves 'Based on 20-Year I Pavement Life Thickness - Bituminous + Surfaces I 4-in. Critical Areas 3-in. Non Critical Areas 1 --+--1-- I in. 1 lb . • 3 4 5 6 7 8 9 10 15 20 30 40 50 Thickness, in. FIGURE 17. Flexible Pavement Design Curves for Critical Areas, Dual Wheel Gear 66 Using either Soil 10 or Soil 20 and suitable asphalt and cement additions to produce a base course material of CBR 100 value and using this material for both subbase and base course for construction of the runway and usage described above, the various course thickness require ments are tabulated in Table 37. TABLE 37. Pavement Course Thickness Requirements (Asphalt-Cement) Soil Subgrade* Surface Base Course Subbase Total Pavement Type CBR Course (in.) ( in. ) Course (in.) Thickness (in.) 10 10 3.2 8.3 4.3 15.8 20 4 3.2 8.3 12.3 23.8 Since only the surface course involves crushed aggregate in this runway model, a total of 3950 yd 3 is required. Compared to crushed aggregate subbase and base construction, this represents approximately 86% reduction in crushed aggregate requirements for the above runway over Soil 10 and about a 90% reduction over Soil 20. Required amounts of other construction materials are tabulated in Table 38. TABLE 38. Stabilization Materials Requirements Soil CBR Cement, ton As pha lt, ton Emulsifier, ton 10 10 440 2177 22 20 4 668 4045 41 To approximate the cost of materials involved in the previously described runway, the following costs were used: Material Approximate Cost, FOB Bethel crushed aggregate $150/yd3 asphalt $250/ton emul sifier $150/ton cement $165/ton *Maximum CBR values from Table 12. 67 These values are believed to be realistic but do not reflect the additional costs of handling, interior transportation, storage, mixing, heating, or application. Table 39 provides approximate runway material costs with various construction options. TABLE 39. Approximate Runway Material Costs Pavement Option Over Soil 10 Over Soil 20 Crushed Aggregate $4,462,500 $5,024,500 4-inch asphalt surface Soil 10 - Emulsion-Cement 5 620,150 $1,127,620 4-inch asphalt surface Soil 20 - Emulsion-Cement S 620,150 $1,127,620 4-inch asphalt surface Soil 20 - Emulsion-Cement $1,257,620 $1,127,620 4-inch asphalt surface For most remote airfield runways the support strength requirements will be considerably less. In many locations, the runway support would be entirely made up from the base and subbase courses which are composed of on-site materials, asphalt emulsion, and cement. For wear and skid resistance, a chip-seal coating of modified asphalt emulsion and crushed aggregate would suffice for years of service. An obvious conclusion from this program is that remote airfield runways can be cost-effectively constructed from Yukon and Kuskokwim Delta materials, asphalt emulsion, and cement, thus utilizing a minor amount of imported aggregate. STABILITY AND COHESION The stability and cohesion specimens prepared for Test Series 2 allowed some time for the cement to react with the aggregate. Even so, the Hveem stability increased only slightly as cement content was increased to 1.5% by weight. R-values of the cement-treated asphalt 68 admixtures were all near 70, which corresponds to a good quality pit-run gravel. Increased cement addition may have been less effective than expected because of too much residual asphalt, which permitted piastic flow during test. In CBR tests of the same admixtures, values over 100 resulted which corresponds to R-values in excess of 88. The R-value measurements which ranged from 7 to 73 and well below the CBR equivalent value suggest that excess asphalt content enabled deformation during test. The R-value range from 66 to 69 without cement and 71 to 73 with 1.5% cement also suggests excess asphalt content. Alternatively, the CBR measurement method may not be as sensitive to plastic flow as the Hveem stabilometer measurement. Normal crushed gravel base course layers will have R-values between 73 and 83. For treated materials, the design criteria require a minimum R-value of 70 for 24-hour cure, and a final cure minimum R-value of 78 after evacuation and backfilling with water. Cohesion increases directly with increasing cement content, but at a lower rate than in Test Series 1. This may also be caused by excess residual asphalt. The addition of 1.5 to 2.0% cement to Bethel soils followed by up to an additional 8% residual asphalt Significantly increased the Hveem cohesion (C) values. With emulsion and cement, the C-values were consistently between 80 and 95. Without cement, the C values ranged from 35 to 80; the lower fines content soil provided the lower C values. The suggested minimum cohesion value (100) for pavements was not quite achieved. The Hveem stability (S-values) for the above described test speci mens ranged from 15 to 19 without cement and 18 to 21 with 1.5% cement. Minimum recommended S-values for pavements range from 30 for light traffic to 37 for heavy traffic, which would further point out the need for a surface layer. Stability and cohesion measurements presently are not used by the FAA ill flexible airport pavement design. CBR measurements are used to determine total pavement thickness and subbase, base, and surface course 69 thicknesses as a function of wheel-loading and departure frequency. CBR and many other measurements are utilized in highway design. A hypo thetical pavement design follows: An approximate correlation of subgrade bearing-strength and soil classification is shown in Figure 7.(4) Soil 10 with CBR value of 10 and Soil 20 with CBR value of 4 may be regarded as poor to medium subgrade materials (see Figure 7). Stabilized Bethel Soil 10 (CBR > 20) would be acceptable as subbase material, or with CBR > 80 acceptable as base material according to Figure 7. Using the AASHO(5) soil support value correlation shown in Figure 18 and R-values of 70-72, a soil support scale factor of about 8 is obtained for Bethel Soil 10. Using the AASHO flexible pavement nomOgraph(5) shown in Figure 19 for low traffic volume (Terminal Serviceability Index 2.0), one obtains a structural number (SN) of 3.0 with an assumed 3000 daily, 18 kip single axle load applications. Applying a regional factor of 5 as a worst case for Alaskan climates, one obtains a weighted structural number (SN) of .3.75. Course thicknesses may be calculated from the relationship where A1A2A3 are layer coefficients representative of surface, base, and subbase course, respectively, from Table 40. (6) 01' 02' and 03 are thicknesses in inches for surface, base, and subbase courses, respectively. For a hypothetical design, assume the following: 1. A compacted base of asphalt-sand (0.3 coefficient) 4-inches thick. 2. A compacted subbase of asphalt-sand (0.3 coefficient) 4-inches thick. The surface course thickness of asphalt-sand (coefficient 0.4) would be 3.75 = (01)(0.4) + (4)(0.3) + (0.3)(4) 01 = 3.75 inches. 70 r- 79 r 795 ,-9 r 23.5 r 20 I- 80 _140 1-70 -120 1= 15 r 76 1-8 -60 -78 14.5 I-- 74 I- 50 - 50 -40 -40 I-- 69 -7 - 36 I-- 9.75 r- 63 I- 30 -30 - 25 r25 I- 20 ~20 I-- 6.75 - 28 1--30 -6 19 - 15 -15 Q) 'iii <0 1-10 Q. If) c: Q. r16 u -5 ell r 11 e-: - 4.5 -12 (f) c: D- o <;j' 0 U ell (") .... N 0 ~ u -7 U (") 0 0 - Q. u Q) E I Q) Q. <0 .... ::J <0 (f) ::J ::J C <0 (f) .... <0 > (f) 1--6 « -8 -11.1 -4 0 -5 « - 2.5 > > 0 c: (f) c: -3 - 3 I- 2.8 r 1.25 -6 r8.2 -2 - 1.5 I- 1.8 '-0.50 -4 I- 6.0 - 1 - 0.5 I- 0.5 r 0.25 -2 I-- 3.0 0 0 1 psi 6.89 x 103 Pa FIGURE 18. Soil Support Value Correlations (5) 71 d, Soil Support Value d, Soil Support Value -n '"~ I • I I I • I ' I I T I I ' I I I I I I I I I I i I I I I I I I', I I I G> N W :P> rn Q) '-l c.o 0 N W :P> rn Q) '-l co c.o C co ;;0 o rn :P> :P> .-. :P> (TIIIIII" (ITTTTTTTlTJTTTTTTi • I I • iii iii I I I l'HHlIlTl"lllil'I'I,nllllll'i' • iii i IT-' I I I I rTT -'"1 Q)rn W N Q) rn:p> W N TABLE 40. Structural Layer Coefficients Developed From Various Sources Stabilizer Layer Material Coefficient Inotel " " // lalSurface . Road mix (low stabilityl,/ 0.20Ia) 0.15Ik) - Plant mix Ihigh /iliiYi 0.441SI 0.301hl 0.25 - 0.34Ii) 0.30Ik) Sand asphalt / 0.40Ia,d,nl 0.201hl 0.251el 0.2Slgl Asphalt IblBase Bituminous treated 0.175 - 0.211gl coarse graded 0.34Ia,bl 0.241ml 0.301dl sand asphalt 0.301al 0.251dl Sand gravel 0.25 - 0.341el Asphalt stabilized 0.101fl (blSase Sandy gravel 0.17Ia,bl Crushed stone 0141') Untreated lei Subbase Sandy gravel 0.111' 1 Sandy or sandy clay 0.05 - 0.1 Ola) IblSase Lime-treated 0.15 - 0.39Ia,nl 0.15 - 0.201hl Lime IclSubbase Lime-treated clay-gravel 0.lSlcI0.14 Lime-treated soil O.lllpl Lime - Fly ash IblBase Lime - Fly ash base 0.25 - 0.301cl 7 -day compressive strength: 650 psi or more 0.23Ia,b,n,kl 400-650 psi 0.20Ia,n) 0.171kl Cement IblSase 400 psi or less O. 151a,nl 0.12Ik) Soil cement 0.20If,11 Gravel 0.171j) Cement-treated 0.15 - 0.251pl 1 psi ~ 6.S9 x 103 Pa Notes for Table 3S: Established from AASHO Road Test a From AASHO Interim Guide, 1972 b This value has been estimated from AASHO Road Test data, but not to the accuracy of those marked with an asterisk. c NCHRP Synthesis of Highway Practice, No. 37, "Lime-Fly Ash-Stabilized Bases and Subbases." IR-l1 d Alabama Ifrom a above I I New Hampshire e Arizona Ifrom a abovel k New Mexico Delaware Pennsylvania g Minnesota m South Dakota h Montana n Wisconsin Nevada p Wyoming 73 A skid-resistant coating would be required. The same highway constructed with crushed gravel for base and subbase, and asphalt pavement surface: 1. Surface is asphalt-concrete 3.75 inches thick (coefficient 0.3). 2. Base and subbase are crushed rock (coefficient 0.14). 3.75 = (3.75)(0.3) + (0.14)(2 D2) 2.625 = (.28)(D2) O = 9.375 inches 2 For a 20-foot wide highway, a comparison of material requirements per mile is compiled in Table 41. TABLE 41. Approximate Materials Requirements/Mile Crushed Aggregate Asphalt Cement Pavement yds 3 tons tons Asphalt Pavement 4278 55 Surface, Crushed Aggregate Base, Subbase Asphalt-Sand 285 550 100 Surface, Base, Subbase 0.5 inch Chip-Seal A second conclusion from this progra~ is that highways can be constructed from Alaskan Delta sands (assuming the Bethel sands are typical), cement, and asphalt emulsion, utilizing minimal gravel. A conclusion from Test Series 1 is that soil, cement, and asphalt emulsion are not to be mixed simultaneously. For maximum strength admixtures, allow the cement-coated, damp aggregate at least four hours curing time prior to emulsion addition. Strength versus cure time of cement-coated aggregate was not established in this program. A four-hour minimum was used in all Test Series 2 specimen preparation. 74 The four hours may represent an excess, but, clearly, simultaneous addi tion of cement, emulsion, and aggregate is unsuitable. The stability and cohesion properties of admixtures prepared from cationic emulsion were very similar to nonionic emulsions. The resilient modulus MR measurements from specimens prepared using cationic emulsion were similar to those obtained from nonionic emulsions. CBR measurements only involved the Chevron CSS-l emulsion. It was concluded from Test Series 2 that there was no significant difference in the mechanical support properties measured in identical sand-cement-asphalt ratio specimens involving the three emulsions. The blendin~ of the two Bethel sands to produce a fine sand with a 15 to 18% fines content resulted in much higher elastic modulus values than either parent material. The optimum silt content apparently lies in a blend of the two parent materials, not necessarily the blend tested. The Armak E 4868 cationic emulsion, specifically selected for the -25 to -35 mV Zeta potential Bethel soils, provided superior strength properties to the normal CSS-l emulsions. Testing of frost heave susceptibility was inconclusive. All of the mixes tested essentially eliminated the frost susceptibility problems of the untreated soils. 75 FUTURE CONSIDERATIONS Sufficient information was derived from this initial study to proceed toward the ultimate goal of airfield/highway construction projects in the Yukon and Kuskokwim Delta areas of Western Alaska. The following studies/projects are recommended in pursuance of the ultimate goal: 1. Softer Asphalt All tests in this program involved emulsions prepared from AC-5 asphalt, primarily because of (a) AC-5 emulsion samples were readily available, and (b) to provide a common basis of asphalt stiffness for all emulsions. If a softer grade of asphalt is to be used it would be expected that stability, cohesion, resilient modulus and CBR values would be significantly different from those of this program. Tests should be conducted for pavement desigr information which would involve emulsions prepared from asphalt of specified hardness. 2. Use of Geotechnic Fabrics The use of geotechnic fabrics was not a part of this program. The use of geotechnic fabrics to improve subgrade support capability and with interlift and intralift installations to increase pavement support strength is presently being evaluated. The use of geotechnic fabrics may cost-effectively reduce the need for imported materials. These programs should be followed. 3. Field Test An installation involving test sections exposed to aircraft taxi traffic is needed to demonstrate that load-bearing capability of admixtures measured in the laboratory perform as predicted in the field. The field test will expose candidate admixtures to conditions very difficult to duplicate in the laboratory. 76 4. Optimized Admixtures The formulations of Bethel soils, cement, asphalt emulsion, and water, selected and tested in this laboratory study, produced mixtures with mechanical properties suitable for field testing in runway and highway applications. This laboratory study did not optimize these mixtures for load-bearing properties or minimum cost. If the results reported in this report are encouraging, optimization studies are probably warranted. 5. Prototype Installation A high priority site should be selected within the Alaskan Delta region for a prototype airfield runway upgrading. The runway requirements should be established, the aggregate source must be thoroughly characterized, the materials and equipment logistics clarified. A prototype installation is needed before proceeding to ' multi-installations throughout the Delta region. 77 REFERENCES 1. Gentry, C. W., and D. C. Esch. 1984. Soil Stabil ization for Remote Area Roads. State of Alaska, Department or Iransportation and Public Facllities, Fairbanks, Alaska. 2. Federal Aviation Administration. 1978. Airport Pavement Design and Evaluation." AC150/5320-6C. U.S. Department of Transportation, Washlngton, D.C .. 3. Koehmstedt, P. L. 1985. "Telephone Conversation With r~r. Rice, Federal Aviation Administration, Washington, D.C .• " 4. Asphalt Division. 1977. Bitumuls Mix Manual. Chevron USA, Incorporated, San Francisco, Callfornia. 5. American Association of State Highway Officials. 1972. AASHO Interim Guide for Design of Pavement Structure. 6. Terrel, R. L., et al. 1979. Soil Stabilization in Pavement Structures. A User's Manual. Vol. 1, p. 18, October. 7. Portland Cement Association. 1966. Thickness Design for Concrete Pavement. 78 APPENDIX A ASTM TEST METHOD D244-83a EMULSIFIED ASPHALTS APPEND r:< ,A, ~ ~l~ Designation: D 244 - 83a Arnencan A!'isooall()l'1 StJlI' Htgnway &nO TransportallOt'! orhOi'll5 Slancw MSHTO No.: T!j Standard Methods of Testing EMULSIFIED ASPHALTS' This standard is issued under the ti.ed desiln:ltion 0244: the number immediately (ollowing the designation indicates the yur d anginal adoption or. in.the case or revision. the year of last revision. A number in parentheses indicates the yeJ.r of last re:lPPro'l-al. A superscript epsilon (f) indicates an editorial change since the last rC,\li~ion or reapprovaJ. I. Scope 06 Test Method for Loss on Heating of Oil 1.1 The methods given under the headings , and Asphaltic Compounds' titled Composition, Consistency, Stabilily, and 070 Test Method for Specific Gravity ofSemi· ,Examination of. Residue cover the examination Solid Bituminous Materials' of asphalt einulsions composed principally of a 086 Method for Distillation of Petroleum 'semisolid or liquid asphaltic base, water, and an Product~' emulsifying agent. The methods cover the follow. 088 Test Mcthod for Say bolt Viscosity' ing tests: 0113 Test Method for Ductility of Bitumi· nous Materials' Test &ctions 0128 Methods of Analysis of Lubricating Composition: Water Content, , ...... , .. , ...... 3to 7 Grease' Residue by Distillate . ~ . , ...... , . , . ,. 8 to 12 0139 Method of F10at Test for Bituminous Identification of Oil Distillate by Micro Materials' Distillation ...... , ...... , .. 13 to IS 0140 Methods of Sampling Bituminous ·Residue by Evaporation , . , ...... 16 to 20 Panicle Charge of Emulsified Asphalts ., 21 to 23 Materials' Consislcncy: 02042 Test Method for Solubility of Asphalt Viscosity (Saybolt Furol) .. , . , ...... 24 to 26 Materials in Trichloroethylene.1 St.bihty: 03289 Test Method for Specific Gravity of Demulsibility .. , ...... , , ...... 27 to 30 Semi·Solid and Solid Bituminous Materials &ttlement , . . .. 31 to 34' Cement Mi,ing .. 35 to 39 by Nickel Crucible' Sieve Test ..... 40 to 43 E 1 Spec.ification for ASTM Thermometers' Coating ..... 44 to 45 E II Specification for Wire·Cloth Sieves for Miscibility with Water 46 Testing Purposes.l Freelin~ ',' ...... ,. 47 Coating Ability and Water Resistance ... 48 to 53 E 145 Specification for Gravity-Convection Storage Stability or Asphalt Emul,sion ... 54 to 60 and Forced·Ventilation Ovens' Examination or Residue...... 61 to 66 Classification Test for Rapid &tting Cationic Emulsified Asphalt ...... 67 to 72 Field Coating Test on Emulsified Asphalts. 73 to 77 I Th~ methlXJs. arc under the Juri§(hctlon of ASTM Corn Weight per Gallon of Emulsified Asphalt .. 78 to 83 miu\.'C 0-4 on Road and Pavsng Matcnab and are the dlrtCt responsibility of Subcommittee 004.42 on Emulsifit'd ASphah. 2. Applicable Documents Tcsu. Current tdilion approv~d March 25. 1983 and June 23. 1~8J. 2.1 ASTM Standards: PubliShed Occcmbcr IQS3. Originally published 3S 0 Hoi .. C 150 Specification for Portland Cement' 26 T. Us,( previous edition 0244 - 81. 2 Aim/wi II110k ,,(A.\'TM.\"IJllulJfas. Pan 1:\ C 190 Test Method for Tensile Strength of ) AmmulllJluk ,;r.1.\TM SI",U/lI,J.\', Vol OJ.UJ. Hydraulic Cement Mortars' •. -4",wtlllloflk of .•.\1M SUllldaft/.\, Vilt M.O! 05 Test Method for Penetration of Bitumi· J Amlllul 8, .. ,1.; of ASf]f Stwlt/lmb. Vul 0" II~ • A,m,,,,/II,H'J. a[A.\TM.\',mulmlb-, VIII~ o~.n.l LInd 1,'-01. nous Materials.l 'A"",IiIIIJ(tok u/ASfA! SIlIlIdiJrtJ.'f, Vol to.tH. A,I I'ARTICLE CHARGE OF EMUL..SIFIED ~t D 244 ASPHALTS NOTE 9-This test is made to identify cntionic emul sions. Positively charged panicles are classified as cati onu.:. 22.3 Adjust the current to at I~ast S rnA with the \'ariabl~ resistor and stan liming with a suit 21. A P pllrul us abk timing deVice equl[>[>ed with a ""cond hanJ. 21.1 Cl/rr('l1/ SUl/rcl!. of 12-V direct current. a NOH 10-The S mA i~ a minimum l.'urrcnt \';JLu,," milliammeter. and a variablc resistor. (Sec Figs. higher curn:nt levels may be spcciJil!d. Current used 5 and 6.) shall be reponed. 21.2 Pftl/('s-Two stainless slecl plates I in. 22.4 When the current drops to 2 IllA. or at (25.4 mm) by 4 in. (101.6 mm). insulated from the end of 30 min. whichever Occurs lirs!. discon· each olher and rigidly held parallel '/' in. (12.7 nect the current sourCe. and gently wash the mill) apan. (S.:.: Fig. 5.) ekctrodes in running water. 21.3 }J('uk,·r. 150 or 25().mL. 22.5 Observe the asphalt deposit on the elec trodes. A cationic emubion will deposit an a~ 22. Procedure preciabk layer of asphalt on the cathode (neg;! 22.1 Pour the emulsion 10 be tested into the tive ekctrode) while the anode (positive elec· 150 or 250-mL beakcr 10 a height that will allow trode) will be relatively clean. the electrod~s to be immersed I in. (25.4 mm) in the emulsion. 23. Report 22.2 Conncct the electrodes. which have been 13.1 Repon the test results in terms of the cleaned and dried. to the doc current source and d~termined rolanty (rosltive or negatlwl a~ de· insen them into the emulsion to a depth of I in. lined lit 22.5. U5.4 mm). APPENDIX A. ASTM 244 Particle Charge of Emulsified Asphalt Emulsion Cathode wt; 9 Anode wt, g ARMAK Pre 24.9942 24.9332 E4868 Post 34.9763 24.8743 Net +9.9821 -0.0589 Chevron Pre 24.9922 24.8721 CSS-1 Post 24.9930 24.8099 Net +0.0008 -0.0622 U.S. Oi 1 Pre 24.9915 24.7999 50A Post 24.9928 24.7489 Net +0.0013 -0.0510 A.2 APPENDIX B ASTM TEST METHOD D 2216-80 LABORATORY DETERMINATION OF WATER (MOISTURE) CONTENT OF SOIL, ROCK, AND SOIL-AGGREGATE MIXTURES APPENDIX B ~~rb Designation: D 2216-80 An A",erlcan National Slandard Standard Method for LABORATORY DETERMINATION OF WATER (MOISTURE) CONTENT OF SOIL, ROCK, AND SOIL-AGGREGATE MIXTURES1 This standard is issued under thc fiud designation 0 ::!216: Ihc numbcr immcdiatcly1"oll('lwing the designation indicates thc year of onginal tldortt~n or. in the C;]~C' l,r rcvlsion. Ihc y.ear of last r~\"i_~i('ln. A number in parentheses indicates the ycar of last rrappro\·al. A superscript epsilon I() lnt.. lle3les an edltonal change since thc 13;1;1 revISion or r('approvaL 1. Scope 3. Significance and Use 1.1 This m.:thod covers the laboratorv deter 3.1 For many soil types. the water content :s mination of the water (moisture) co~tent of one of the most significant index properties soil. roc~. and soil-aggregate mixtures by used in establishing a correlation between ~oil weight. For simplicity. the word "material" behavior and an index property. hereinafter refers to either soil. rock. or soil 3.2 The water content of a soil is used in aggregate mixtures. whichever is most applica almost every equation expressing the phase ble. relationships of air. water. and solids in a giv:n 1.2 The water content of a material is de-· volume of material. fined as the ratio. expressed as a percentage. of 3.3 In fine-grained (cohesive) soils. the con the mass of "pore" or "free" water in a given sistency of a given soi~ type depends on its mass of material to the mass of the solid ma water content. The water content of a soil. terial particles. along with its liquid and plastic limit. is used to 1.3 This method does not give true repre express its relative consistency or liquidity in sentative results for: materials containing sig dex. nificant amounts of halloysite. Rlontmorillon 3.4 The term "water" as used in geotechnical ile. or gypsum minerals: highly organic soils: engineering. is typically assumed to be "pore:' or. materials in which the pore water contains ot "free" water and not that which is hydrated dissolved solids (such as salt in the case of to the mineral surfaces. Therefore. the Wl\ter marine deposits). For a material of the previ content of materials containing significant ously mentioned types. a modified method ~f amounts of hydrated water at in-s~tu tempera testing or data calculation may be estahlished tlM'es or less than IIO·C can be misleading. to give results consistent with the purpose of 3.5 The term "solid particles" as used in the test. geotechnical engineering. is typically assumed to mean naturally occurring mineral particles 2. Summary of Method that are not readily soluble in water. Therefore. 2.1 The practical application in determining the water content of materials containing extra the water content of a material is to determine neous matter (sucb as cement. etc). water-sol the mass of water removed by drying the moist uble matter (such as salt) and highly organic material (test specimen) to a constant mass in a drying oven controlled at 110 ± 5·C and to I This method is under the jurisdiction or ASTM Coma millce 0·18 on Soil and Rock and is the direct responSibility use this value as the mass of water in the test of Subcommiuce 018.03 on Texture. Plasticity and Density specimen. The mass of material remaining after Characteristics o( Soils. oven-drying is used as the mass of the solid Curren' edition approved May 30. 1980. Publl!liihed July 191<0. Onglnally puhll"het.l as l) 22111 - 63 T. l...O1!1.l prcviou!'ii particles. edillon 02216-71. • B.1 02216 matt"r typically require special treatment or a 6.2 The manner in which the test specimen qualified definition of watcr content is selected and its required mass is basically dependent on the purpose (application) of the 4. Apparatus lest, type of material being tested. and the type 4.1 Drying Oven, thermostatically·con of sample (specimen from another test, bag, trolled, preferably of the forced-draft type, and tube, split-barrel. etc.). In all cases. however, a maintaining a uniform temperature of 110 ± representative portion of the total sam pie shall S·C throughout the drying chamber. be selected. If a layered soil or more than one 4.2 Balances, having a precision (repeatabil soil type is encountered, select an average por ity) of ±0.01 g for specimens having a mass of tion or individual ponions or both, and nOle 200 g or less, ±O. I g for specimens having a which portion(s) was tested in the report of the mass of between 200 and 1000 g, or ± I g for results. specimens having a mass greater than 1000 g. . 6.2. I For bulk samples. select the test speci 4.3 Specimen Containers-Suitable con men from the material after it has been thor tainers made of inaterial resistant to corrosion oughly.mixed. The mass of moist material se and a change in mass upon repeated heating. lected shall be in accordance with the following cooling, and cleaning. Can tainers with close: table: fitting' lids shall be used for testing specimens .Recommended' Minimum havinl; a mass of less. than, about 200 g; while . Sieve Retaining More Than Mus of Moist Specimen. for specimens having a mass greater than about Aboul to'" of Saalpl. S 200 g, containers without lids may be used 2.0 mm (No. 10) sieve 100 10 200 4.75 mm (No.4) sieve )00 to 500 (?~ote I). One container is needed for each 19mm 500 to 1000 water content determination. 38 mm 1500 to )000 76mm 5000 to 10 000 NOTE I-The purpoSe of c1ose·fitting lids is to prevent loss of moisture from specimens before initial weighing and to prevent absorption of moisture from 6.2.2 For small (jar) samples. select a repre the atmosphere following dryinl! and before fmal sentative portion in accordance with the follow. weighing. ing procedure: 4.4 Desiccator-A desiccator of suitable size 6.2.2.1 For cohesionless soils. thoroughly (a convenient size is 200 to 2S0-mro diameter)' mix the material, then select a test specimen containing a hydrous silica gel. Tliis equipment having a mass of moist material in accordance is only recommended for use when containers with the table in 6.2.1. See Note 2. • having close-fitting lids are not used. Sec 7.4.1. . 6.2.2.2 For cohesive soils. remove about 3 mm of material from the exposed periphery of S. Samples the sample' and slice it in half (to check if the 5.1 Keep the samples that are stored prior to material is layered) prior to selecting the test testing in noncOlTodible airtight containers at specimen. If the soil is layered see 6.2. The a temperature between approximately 3 and mass of moist material selected should not be 30·C and in an area that prevents direct contact less than 25 g or should be in accordance with with sunlight the table in 6.2. I if coarse-grained panicles are 5.2 The water content determination should noted. (Note 2). be done as soon as practicable after sampling. 6.3 Using a test specimen smaller than the especiall) if potentially corrodible containers minimum mass indicated previously requires (such as steel thin-walled tubes, paint cans, etc.) discretion, though it may be adequate for the or sample bags are used. purpose of the tesL A specimen having a mass less than the previously indicated value shall be noted in the report of the results. 6. Test Specimen 6.1 For water contents being determined in NQn 2-ln many. cases. when working with a conj unction with another ASTM method, the small sample containtng a relaltvely large coars. grained particle. it is appropriate nOl to include this method of specimen selection specified in that particle in the test specimen. Jf thiS occurs. it should method controls. be noted in the report of the results. B.2 02216 7. Proccdurc bare hands and the operation of the balance 7.1 Sclect representative test specimens in will not be affected by convection currents. ncc,'nJu",:e with Se~ti"n b. Determine the mass of the container and oven 7.2 Place the moist specimen in a clean. dry dried material using the same balance as used container of known mass (Note 3). set the lid in 7.2. Record this value. securely in position. and determine the mass of 7.4.1 If the container does not have a lid. the container and moist material using an ap weigh the cOl,ltainer and material right after propriate balance (4.2). Record these values. their temperatures are such that the operation 7.3 Remove the lid and place the container of the balance' will not be affected by convec with moist material in a drying oven main tion currents or after cooling in a desiccator. tained at 110 ± 5°C and dry to a constant mass NOTE 7-Cooling in a desiccator is recommended (Notes 4. 5. and 6). since it prevents absorption of moisture from the atmosphere during cooling. NOTE 3-To assist in the oven-drying of large test specimens. they should be placed in containers hav ing a large surface area (such as pans) and the material broken up into smaller aggregations. 8. Calculation NOTE 4-The time required to obtain constant 8.1 Calculate the water content of the ma mass will vary depending on the type of material terial as follows: size of !ipecimen. oven type and capacity. and other facton.. The influence of these factors generally can w. be established by good judgment. and e'peri~nce w-[(W,- W,)/(W,- W,)jx lOO--x 100 with the materials being tested and the apparatus W. being used. In most C3ses. drying a lest specimen over night (ahout 16 h) is sufficient. In cases where there where: is doubt concerning the adequacy of drying. drying should be continued until the mass after two succes IV - water content. %. sive periods (greater than y, h) of drying indicate an W, = mass of container and moist specimen. insignificant change (less than about 0.1 %). Speci g. . mens of sand may onen be dried to constant mass in W, - mass oi container and oven-dried spec- a period of about 4 h. when a forced-draft oven is used. imen, g,. NOTE S-Oven-drying at 110 ± SoC does not W, - mass of container. g. always result in water content values related to the Ww - mass of water. g. and intended usc or the basic definition especially for W. - mass of solid panicles. g. materials containing gypsum or other minerals hav ing Significant amounts of hyJratcd water or for soil containing a significant amilu"t of organic material. In many cases, and depending on the intended use 9. Report, for these types of materials. it mig!!t be more al'pli cable to mamtain the drying oven at 60 ± SoC or use 9.1 The report (data sheet) shall include the a vacuum dC5iccator at a vacuum of approximately. following: 133 Pa (10 mm Hg) and at a temperature ranging 9.1.1 Identification of the sample (material) hetwcen 23 and 60°C for drying. If eit~er of the,e being tested. by boring nu.mber. sample num drying methods arc usco. it should be noteO in the repon of the re.ults. - ber. test rumber. etc. NOTE 6-Since some dry materials may absorb 9.1.2 Water content of the specimen to the moisture from moist specimens. dried spccimen~ nearest 0.1 % or I %. depending on the purpose should be removed before placing moist specimens of the test. in the oven. However. this requirement is not appli cable if the previously dried specimens will remain 9.1.3 Indication of test specimen having a in the drying oven for an additional time period of mass less than the minimum indicated in Sec about 16 h. tion 6. 9.1.4 Indication of test specimen containing 7.4 Arter the material has dried to constant more than one soil type (layered. etc). mass remove the container from the oven and 9.1.5 Indication of the method of drying if replace the lid. Allow the material and con different from oven-drying at 110 :: '!i 0c. tainer to cool to room temperature or until the 9.1.6 Indication of any material (size and container Can be handled comfortably with amount) excluded from the test specimen. B.3 ~~l~ 02216 10. Precision and Accuracy curacy of this test method have not yet been ·10.1 Requirements for the precision and ac- developed. The Amt>ricalf Socit!t)' for Testing and Matrria/s lakes no position 't!specling th, valid,,}, of any palt!ltt rights QHerted In con#l~c/fon WIOI any ittl," mt!ltliont!d in this standard. USt!I'$ oJthif standard art! uprt5SIy Qd~·jsed Ihat determination ofInt! vaiidtty of any such palent righU. (JIIIi th~ risk. of infringement of such ,igJus. art entirel), tnt"" own rtsponsibilily. This staffc/ol'd is subjeCllo ulI;sion at any ,im," by II" re.'rponsible technical comm;tltr and musl he re'-felt1eli t'lerYJi"t y,ars and if 1101 re'lised. either rt!opprolled or withdrawn. Your comments a" iltlli't!d eilher for relli.f;on o[ Ihis standard orfor addillonal slilruiards Qnd should Iw addussed 10 A STM HeaaquarterJ. Yo", commenlS will '~U;lI' cD,,/ul consid"alion al a m~"ing 0/ th~ '~JPons;bltltclrn;C'al commilltt. 'It'lrielt you mIl;V alltnd. 1/ you/ttl ,hal you, commmlS hallt nOI "U;lItd a/a;r htaringyou Jhould IMkt your vit'NJ known 10 Oft ASTM Commill~tOn Siandarcb, 1916 Rau SI" Philadelphia. Po. /91OJ, B.4 APPENDIX C ZETA POTENTIAL TEST METHOD APPENDIX C THE ZETA - METER The Standard ZETA·METER shown with our new Zeiss lib stereomicroscope ZETA POTENTIAL FOR OPTIMUM PRECIPITATION OR DISPERSION OF COLLOIDS ::TA·METER, INC. • 1720 FIRST AVENUE, NEW YORK, N. Y. 10028 • TEL. 212·348·4100 • CABLE ZETA·METER C.1 CONCEPT OF ZETA POTENTIALt The stability of a colloid system or emulsion is dependent For ,ISSlIred stability, each colloid must retain complete dis upon adsorption of ions (or polymers) from the bulk of the cretencss with I/O agglomeration. This discreteness may b suspending liquid. There are three present methods by which achieved by: the colloid can be stabilized. In each, Zeta Potential reveals the actions and produces data which permit suitable adjust a) Adsorption on the colloid of an .In ionic electrolyte a ments to the stability of the system. polyelectrolyte, to cre;lte strong mutual repulsion. Substantially all colloids, both organic and inorganic, are b) Adsorption of a strongly hydr:lted hydrophilic protecti\' electronegative when suspended in either distilled or tap colloid such as gelatin. on a larger hydrophobic colloid '\",lter; that is to say, aqueous suspensions of low ionic concen In this case, the affinity for water exceeds the mutua t~.!tion in the pH range of ~ to 10. Moreover, the Zeta Poten attraction of adjacent particles. ti.!l of such systems generally ranges from about -14 to -30 millivolts. Proteins also fall into this category, but they become c) Adsorption of a nonionic polymer of sufficient chai less electronegative with decreasing pH, and their pH-ZP length to create stcric hindrance. to prevent two particle curves generally cross the line of zero charge in the pH range coming close enough to jOin. This method IS widely of 2 to 5. employed for emulsions. Zeta Potential values less negative than -14 millivolts usually represent the onset of agglomeration. A plateau region, These three mechanisms are shown on Fig. 1. marking the threshold of either coagulation or dispersion, e:'(ists from about -14 mv to -30 mv. Values more electro When coagulation is the desired end, Zeta Potential mus negative than -30 mv generally represent sufficient mutual be rendered less electronegative in order to reduce the forces repulsion to result in stability. However, to afJllre stability of mutual repulsion. Gentle agitation will then create im with a reasonable factor of safety, Zeta Potential should be pingements of particles which enter the region where the short increased preferably to the range of say -45 to -70 mv. range Van der Waals-London forces C:ln furnish the attraction required to cause agglomeration. Optimum coagulation usually One cannot categorically state that a colloid will or will occurs in the Zeta Potential range of 0 to + 3 n1\', MaSSIve not be stable at a given Zeta Potential, particularly in the deli agglomeration is aided by emplo)'ing a long-chain polymer to cately poised range of -15 to -30 mv, l!ut certain broad provide mechanical bridging, in adJition to Zeta Potential generalizations may be made. The writer's experience with control. anionically dispersed systems, based on the Helmholtz-Smo luchowski* formula is: THREE METHODS FOR OBTAINING COLLOID STABILITY A'·J. ZP Stability CharaneriJliC'I in miilivoJu .~ ~~,. - " ~(aximum agglomeration and precipitation ...... o to +3 -~ .. Range of strong agglomeration and precipitation .. . +5 to -5 , Threshold of agglomeration ...... -10 to -15 Threshold of delicate dispersion ...... -16 to -30 : Moderate stability ...... -31 to -40 Fairly good stability ...... -41 to -60 Very good stability ...... -61 to -80 METHOD 1: Mutual rcpulsion due to hi~h Zeta Potential ExJremeiy good stability ...... ,',."." .. , .... . -81 to -100 A possible e/erlropositir'e range of dispersion of zero to at /' protective least 70 mv is possible, but is seldom employed by either ,-.-w.{' colloiJs - "'# ...... •... ".0 + .... , .~ \ .. Nature or man. II' '.. :I \ . At any given electronegative Zeta Potential from zero to , : ~ I ~ " \ I about -15 mv, the degree of agglomeration can be markedly '- .' ,\, 01' improved by also employing a suitable long-chain polymer to ~6.'" ~.d' produce mechanical bridging. ** However, at Zeta Potential METHOD 2: Adsorption of a small lyophilic colloid on a values more electronegative than say -15 to -25 mv, true larger electronegative colloid colloids (equal to or less than 1 micron size) in dillite sus pension often fail to show any agglomeration upon the appli , \ ( ~ \ cation of either an anionic or non ionic long-chain polymer. It will later be shown that certain natural systems (skimmed "--~~.(./ L "~/:~ milk, for example) exhibit absol1lte dispersion at relatively ~ ;. --::t x:- low electronegative Zeta Potentials. This seems to be the - ~ ( -~ \ / ~ '-----... result of Nature's nicely matching the dispersant with the colloid. ./'mY~, '\ 7'A !'--r--Y /\'\ 'No si.~nicant difference will be found if one employs Henry's J \ '. '/ \ \ formula with Overbeek's correction for "time of relaxation," METHOD 3: Storic hinJrance Jue to adsorption of an •• LJ~fer and co-workers have dealt extensively with this phase. from oriented non ionic polp:lectrolyte both theoretical and practical aspects. team,olof Colloid SlabililY Ih,OUKh Zela POlenlial - paJe! 2 & 3. FIGURE 1 C.2 APPENDIX C. ZETA Potential Determination Aggregate 1. Fill the electrophoresis cell with sample. 2. Determine specific conductance and select voltage. 3. Measure transit time of 'ten particles minimum, record voltage, transport time, sample temperature. 4. Using ZP-EM chart, determine electrophoretic mobility. 5. Determine ZETA potential (ZP) using ZP = 4n Vf x EM Dt Vt = Viscosity of test liquid in poises at temperature Dt = Dielectric constant of test liquid at temperature Asphalt Emulsion (ARMAK) Method) 1. Make up emulsifier in distilled water exactly the same con centration as in asphalt emulsion. 2. Fill electrophoresis cell with dilute emulsifier. 3. Add five to ten drops of asphalt emulsion. 4. Determine emulsion ZETA potential as with aggregate. C.3 Temperature _~_orrection hctors .(' Zp· EM CHART ) .. t , '(,; , ~ -.L 30 88 25 .95 21 1.03 -;-i--16 (Use with "f&'L type ocular micrometers only) 29 89 24 97 20 1.05 I~ ~~-1 17 26 90 23 99 19 1.07 14 1.20 27 92 22.5 1.00 16 1.10 13 1.23 26 .94 22 ilOI 17 1.12 17 126 ZP. Chari Vdlue of ZP x Te~Corr.ction· -~ Average time in seconds for traverse of one std. micrometer division & I , . 1 -.l '5 2 25 3 5 7 10 10 .' 9 1"'10.. I'- ~ I ...... I' ...... - 0 ...... 7 "'" " ~ i"' '..1...... 1'I!o. .$1'. i'" 6 .0 5 ~ , , I ~ l!- • >.45 V. oc: 40 (I) 35 E rp 2 30 .! , (I) , , I I 2 ..... ~ L:'" ~ en> 25· l"'!o (I) .... I..... !"Io. , .... I 520 , :'!!o ~ 15 II) ."" ~ ;:, "" a' 1'00...... f'" :IJ "'" I.... ~ ~15 ...... ~ i'. 0 !"o PI'I. o ...... ~ ~ LO in , :'!!o N '" 9 N 0 ...... i"'o 8 r.. 2 , I .... 15 ~ ~ r- ..... - i" - I...... -, , !"o.. 1 10 15 20 25 30 40 50 60 80 100 12 5 150 Average time in seconds for traverse of one std. micrometer division C.4 APPENDIX D AGGREGATE SURFACE AREA APPENDIX 0, PART 1 yo&. ... !400. • ...°w - ..... o_..,.n._ ...... c.. _.c· ...... THE ETHYLENE GLYCOL MONOETHYL ETHER (EGME) nx:HNIQUE FOR DETERMlmNG SOlL-SURF.\CE AREA Y.. D. HEa YA..'i. D.. 1.. C.~RTER. AlIa C. L. GONZALEZ Ulliled &aut 0.",,"--, 01 A,nc.u..,.· _ ... f. pabh tiM .... It U. TuIaI ..".. ... iI III importaD, fUDela f_ horimm, tbe tutural B or a bon- '*' a .... IIIil propeny. '11IiI property is m.-red depth 01 38 inehea, &lid a bon- from below to ...... die propon.iuo 0I1a\""", el.. ~1a is inch., where little weathering bad oceuned. ..,. IIIiljoe_ iD IoiII ADd to _ lOil phyait'.&l In addition, four surface !!Oils UIII!d in pftIYiouI ... ~'" propera.. Dyal ADd Hendricb surface-area studiel at the U. S. SaIiaity (.) ~ a IDIItbM for -rma surface Laboratory wen includeci. The soil., bo';_, ... 01 ..,. ___ '11IiI DIIRbod waa modi- and deptba an listed in table 1. W ... Idapt.ed to IOiII by Bower &lid Air-dry aoil IIIDplei wen cround to pall a C 11au_ (1). sw.q.adJ. Mart.iD (6) pro 600meIh Iieve, treated with :a.o. to deI&roy or JDIIla modift'doa 01 the Dyal ADd Heudricb ganic ma&ter. ADd wubed with tueeeMive quaD ...... (.) f. Ia,.. IIIiljoe_ HiI modification titiel 01 N CaClo for c-turaUnc. ~ 111\ iDeIudIcl a IIJIINI 01 f. edayleDe pycol ill the waa I'8IDOftd by three 111m iva water W&IIb Ift_.... dPri .'Ior to ocmWOl die YApor preI inp. Then the IIIDpiee wen dried ADd apiD .,. vi ...,. II1col a~ the miDera1 IJOrption II'OIJIICi to puI a ~ .... --. .lower _ Ooertae (2) modified the Sis replicate 1.1"" IIIDpI. of each IJOil weN ~ ~ by Mart.iD (6) ADd adapted it placed ill abalIow aluminum weichiDI eaIII and f. ...uriDc IJOil llU'faee ana. Thill latter dried to COIIIteD~ weight. ill eftCIUated dIIIIio IDI&boIl iI ocmeM!ered to be III equilibrium caton OYer P.o.. One crouP of dupticate ...... (2) ADd iI widely UIIId today. A JimiIar ampl. waa treated with Ippluximately 3-ml. ba& ... compja DIIRbod waa inirodueed by portioDl of reapnt-pac!e ethylene glycol for de 80r _ JUmper (7). All tt.e methodI ut.ilbe terminiDg the glycol reteDtioa ADd 1UIf_ area aday1eDe &lJeoi, a hicbIY polar moleaule, II the by the Bower aDd CoerUm method (2). A .-w pMa They all haft the common die glycol-CaCJ. IIOlvate waa pnpaftd aDd p1aeed in ...... 01 beint very time LlOIJII'miDg. a cuitun diIh beneath a eupporting .... The BeeeatJy, Carter a at. (3) introduced a sample eaIII wen plaeed 011 the ecr.n. ADd tbe IDI&boIl for determiniDg the surface area of lid wu placed on the culture diID, usiDc a IIIIall layer .'joe_ ill which the IdIorbed phue Will bloe.k to leave an ~pproximately 2-mm.-wide __ PYeol lDOIIOethyt ttber (hereafter re space between the lid &lid dish Cor ca- to _ f.... to u EGME). The method is I!imilsr to cape. The entire culture diIb .. p1aeed ia a ba~ maoh IlION rapid than ethylene glycol vacuum __tor contaiDinc eac.. The par ..... '11IiI paper reporil I'I!IUlti of adaptinc poIIII of the cuitun diIb ADd IIOiVllte ... to tM EDM£ method to IOiII, the agreement be maintain a COII8tUIt "ycol vapor pr 'n at tnaa tbe pyeol ADd EGME methoda for the IJOrption 1W'f_ 01 the IJOiI. The el700Huil IIIiII, ADd a ~ routine method for deter- lIurry waa allowed to equilibrate o.uaaicld 1DiDiDl1JOil..".. area with EGME. befon the desiecator waa evacuated for 41 miD utes with a higb-yllCUlllD pump. The fteiiWD IIDTIIODe .urD MAftaIALI attained after 46 ~ ...... " '11II111i11 Mdied iDcIuded four horilona (rom 0.250 mm. He. ADd the ItDpcoeb weN ebed ... 01 eiP~ irripted IOU. of the Lower Rio to main the YIICUIIID. The liM weicbiDI ... 0rudI V..,. 01 TCIIII. Soilamplel from four made appaoximately 72 hoan after the liM ~ which reprumted tbe ranee of prop --. After MCh wei&biaIt the 1 . InIon ... ia the pro6II 01 each IJOil type. wen _ wen re-encuated for 46 aainnateL W...... waa _aa-t M :u-bour interft111EIIiil a __ ..... f. l&Udy. on- included the two IUJ'- staat 1fIfliIIR ... attaiDed. ·W...... -r- Apprceim'tely 3-ml. partiaaI 01..-.... 0.1.1 410 TABLB I EGME _re Idded ro NCb 01 another .. 01 s.a. 111M /.,. _ .... ;.., ...-.... ., d.Unon.. i .., duplieate _pia The mmtioD "I EGME __ det~rmioed by the IMthod propolll!d for Ia~r -"--1-- silicata by Carter d al. (3). This method ill (iLj eluded aaEGME-CaCIo lIOI\"ate placf!d iD cul I-w nu,l cJ,q IMM ture diaheI, l1li dlwriLed previowlly. ro maintain Alp 0.1. 2 ,*,WiillCllllU IIOIL-et;U4CS ,...... tIae ob«ained WIiDc dycol with ('()IItroll<'d 250 pycol qpor ~ • tic. 2). 'IMee !'!'SUIt.! ~ jM"te that the cootzol of vapor presure is N. AlG) - '·0' AIEGliE) - 3.9 E 2 DOt importaDi wbeD EG~IE is t-t .. the ad r .0.9" -tJed pIaae. Ac\ually, the ,-alues repornd pre o· ! YiouIIy for clycol, with and witbout CaCI. 0 ISO PYeoI l1li.,.. to control vapor pressure, did ..• DOt diIf.. patly (2). 8inre only a (ew hoo!'! 0 an required lor attainins monolay~rs o( .. -" 100 EGME, coatroi ol vapor p_re appears UD • Dell!....,.. § Surf_ area vaiuee det~nnin~ by EG~IE "0 SO me&hoda with and withoui CaCIrEGME sol u... va. (or vapor p_re control aIao were com c: pared. The relation iI i11l11tra~ in figure 3 00 50 100 150 200 250 (EOME. refers to the use of the CaCIrEG~IE EGME surfae, area, m.2/g. lIII.,.te). Some variation occurred, but it was DO pater thaD the random variation tbat nc FIG. 2. Relation betwo!en lOil_Mace area de"'.... curred bet_ duplicate runa within any of the minN.I by ~be glyco! method with controlled .. apor tbft!tI mf!lthoda (table 2). The variation bfotween prelllUre &lid the EGME met.. od with no .. apor pl'!'''''Il't' ('Qntro!. duplicate runallllins glycol was greater than that fOUDd between methodl (table 2). The probablp explaDatiOil for thiI variation is that sam plel! tained per gram of soil are aIao presented in are handled and expoeed to the atmosphere table 2. The intl'rcepts (or all regl"Cllllior.8 are more duriq a eneral-day run with glycol than near the oricjn, and the slopes approximate they are with a Bingle-day run with EGME. unity. As report~ previously, a slightly greater AIIIo, averqiDl duplicate runa withm each mass of glycol than EGME is required to (onn method belore method.'! were compared de a monolayer per unit surface (3). This differ creased the random variation. ence, however, is only about 7 per cent and is The resr-ion eoetIicienta, intercept values, one that is not evident because of random varia and colT1!lation eoeftici~nta (or comparisons tion among samples. hetween methodl (or milligrams adsorbate re- Since method.'! using EGME and glyeol give the same .results for soil-!!ll.-face area, the mOlit convenient method should be u!'ed. In our 250 laboratory, the glycol method required from 4 ~ A(G)- S.8 + 0.92A(EGME ) to 'i days to obtain equilibnum monolayel'l! N. s on t soiLs E200 , - 0.98~ hc P.O.-dried studied. In contrast, the maxImum time required for EGME was 2 days, •o :lIld many sam pies could, i( desired, be com :; 1110 pleted within one day. Using EGME saVl'l! • considerable time and iI more convenient than ..o the glycol method. When using EGME, the 't: 100 P,O, drying becomes the most time-eOD8UlDing •" part of the procedure. It may be po.s!ible to O\'en-dry samples to save time, but the effect 110 '0 of o\'en-drying on surface area would have to ..... he e\'aluat~ . ii Studies with different numbe!'! o( samples SO 100 150 200 250 per desiccator indicated that samples should not EGliEs aurfoe. area, rrf!, IQ. be crowded. Precision was increased and time saved by placing a maximum o( 6 samplea per Flo. 1. Relation between lOillW'1ace &rea d~ter mined by the glyeol &lid the EGME. method!! de:,;ccator (2!iO-mm. J.D.). When Irt!Iter num with controlled Yapor p~. be!'! of .wnpiea Wl're U8ed, precision deereased. 0.1. 3 412 pm Mt., C&a'I'D, .urD ~ '-_ .. ill the __ted dflIIiceatu T.UU.B l MIIorW ...... other samp~ _ while ~ ---,. .... ,... ..,...... ,...,. beiac • ·,bed. TIle pater the exposun. time rr/." .. ~ ...-.n- ~ .,~ to die -'tal "'J '-eN the crater .... the UDOUIlt .-...... "u-...... _. 01 moiI&unt IIIiIorbed. "-- of ftI/- - ..,... • :a-tly, MeNs! (8) reported tba& the ...... ~ s_ ... importaD, ill lIUJ'f_aftIl r :r • ciPtenDiaa.... by the II)'CIIl method beeaIIIII' of muiUpie -ua_ o( zlycol moJeeula with certaia atura&iDc stioDL Ii is probable thai _,.I,. I ...I,. t ...II. ' EOME moleeulel similarly _iate wil h satu --- -~--I·---.- --'--f-- ratiDI eatiooa, beeawIe the two materiala g.'lve EO ...• I '.1 O.II! •. ". the _ resuitl for C_tunated samples. EGO I ..... I'" ; .... The EOME method, rUl or without CaCl. I EOO ; -u i"" : t .• EOME IDlvatel to control vapor prelllUre, is .....derably mont rapid than the glycol y--_.- medMld, aod it zivl!lI reeuitl that are equally w./,. w,/,. '~LI u.IuI. Neither materbl ill the probable ulti mate for meuurinz the actual surface area o( 0.".,., .., I ~ .... J -1.1 i .... I .... EOIlE. • ..,11 BOD. • ..,' 1.1 I '.If •.• IDiII aod 1IIiDeraII. There is a need for a more I • oM _ ~. CoCI ..EGO __ diree& meuunt of the actual lOil and miDerai 10-..n...... -.. ___ • .-,. 811 ..__ 1IUJ'f_ area, but no IlUch method baa been de veloped. Uatil IlUch a method is introduced and pl'Oft!D, the EOME proeedunt appe!U'!l to be the thia laboratory. The proeedure could be alteftd IDOR coavem.t method to obtain fI!lIulti that somewhat without 10. of preeiliaD. ant IJII8lu1 aDd thai ean be related to other Rec:ormMItCIecI proc4IIiure miaeral aod IOil propertiel. A OOIlWllieai procedunt for lOil-llUrface area, Approximately 1.... _p~ ant dried to eoa IIIIiac the EOME method with or without a stant weitht over p.o. in aD evacuated dI!lIic CaClrEGME IOivate, baa been developed at cator. At the beciaaiDc of a workiaz day, sam ples are treated with approximately 3 mJ. of 1110 EGME to forn a soil-EGME slurry that ill ACEGME.).'.06A!EGME) - ~.9 placed in; a delliceator over CaCJ. and allowed .t to equilibrate 30 minutl!ll. The dellieeator ia thea "'e 200 ,. O. 96~ evacuated for approximately 46 miDuteI. About .; one hour before the end of the workinZ day, the • samples are weighed aDd the __tor re Iii tao evacuated for 46 miDutes. At the bezinnillZ of the next working day, the samplel ant apia •u weighed. Generally thia latter weitht will &cree .! tOO ,... very cioeely with the pntvious wei&ht, iadicat • ing that a coDBtant weight baa beea attained. If III• all samples have attained a colllt&Dt wei&ht. a 2 50 0.1.4 ~13 fan _ nf ,.,.. aDd ""... by sa ....lC4b "WIt .tbv\low IiYt'OI _tbod. Sl>d :1M. Sf: E&IayIme Ib"llOI aDd roME (rtbykooe glyt'Ol 2S-2!lt. -.111,1 f'dwr) (lift the _ -"I'P nf ,od (3) CartoPt-. D. L. antman. :0.1 D. aad Goua.Ira. -'- _ The roME IIIf'tbod is ooaWDieat C. L Ethyw- Id~ _til~1 rtiIH (or ...... _ rapid IJIua the etb,._ cIyeoI ..~t.f'tIIIiaiIlI !!UriIlOl' .... 01 atirale DUDHUI . a.tbod. EGME eua be lad u the IdIIorbed SoU Sci. 100: 3..I8-3l1O. (t) ~. R. S. ad U.. Ddnt-b, S. B. 19GO To~ ..... ill the pi 01' .-- 01 a CaOr -m_ _ of a.,. iD poiIIr liquid. •• EOME 101ft.. to eoatrol npor p.-uoe with r~ iDda. SoU sa. .: 421-42...... of IIIIIfaN area.. A proee (5) MartiD, R. T. 1111 Etb,.... alYeo' ... tea ..... ~ for IIIiDI the EGME nmhod lioa by eJa,.. SoU Sri. Soe. Am. Proe. I.: I'OIRiDeIJ ill the Iaboratol'J. 1~16t. (S) MeNeai, B. I.. 1l1li Uf'et of .. st~ REFERE.'JCE8 catioM OD ~yeol ...teDtiOD by ''''T miMraia. Soil Sci. 97: 9&-1112. (I) Bower, C. A~ ad G.,b~d, F. B. 1952 (7) Sor. K~ aDd Kemp"r. W. D. 1958 F..otima Ethy.... IIYcoI reteutioD 01 IOU. ... m_ tioD 01 bydraleabie -m..:e 01 IOU. aDd .:Jay. ... 01 ___ aDd iIlle~r awellial. from the UIIOIIIl\ of abeorptioa IUld ...leo Soil 8ei. 800. AID. Proe. II: 3G-344. tioD 01 etily\elll! dYeo!. Soil Sri. Sot!. AID. (2) Bower, C. A~ aDd GoertaD, J. O. 1958 Sur- Proe. 23: 10&-110. 0.1. 5 APPENDIX 0, PART 2 DETEKMI~I~G SURFACE AREA SU,\1MAIH Th,s procedure will rielCrrtllflC the J\aifable surface area oi a ~p('ciflc minerai or rockrype. The surian,' area,>, in m~/g, can be used for comp.Hison bel'.vt'en minerals or a possible correlation belween surface area and sorptton. MATERIALS \'\"cishing cans Balance (tenths of a rndli~ram) Des!'d(,CJIOr Anh"nrous CalcIum Chloflne (CaCI,) Phosphorus penta>ide iP,O,1 Centrdu!!e C('nlriru).,:t> Tuhe,> 1"1 A~~o) .:.oiutton 2,'\.1 Cael: ~olul!On tth .... lt!nc Ciycol ,"onoethyl Ether (E.C,\1E. Ihe aho;orhate) HAZARD 1. Handle P.,O, (",lIcfuliy as It rCdCg ..·.dr. dlr or H.-a 10 produce pnosphoflC J( 10. \".. hich can 0(" c.ln~erous. PlurARF SAMPI E 1. Place 1 g of sampie In a 2 N C.)C:~ ~ui~tiun \-10 ml) In a centrdugf> tube. 2. Stir or shake Ihc sample' for 5 min 3. Ccnlriiuf!e lor .2 mIn a[ 5000 rpm ~.1tur.)lt· S.lInplt· 5. "dcJ diqi!)pd H:O (-10 mil to the ~~rnpl(> tor the purr0'>c Of rpnloving the chlurides 6. Sw and centrifuge. 7. Remove a small amount of the ,>upernatant. 8. Tpst the supernJtant for chlorid(· wtlh a drop or lwO of 1 {\1 Ag/\",'o). NOTE: The supern,ltant will tuf.n rnilk\" if chlorides are rr('scnt. 9. Rep£>al steps 5-8 if chlorides are prl''>cnt. 10. Remove the resl of dw sUI1c>rnat;HlI from the s.)mpfe d no chfollde~ .)1(' rre'>('nl. 11. Dry \.lmpl(, ~n Ih.11 all H:O i, rl'moved or ("'rrors may (l''>ul! in CJfcUJ.llir.~ !lurfan? arcas. 0.2.1 OI'ERA TlNG PROCEDURES 1. \\leigh all weIghing can(" without samples ([are weIghts), uSlflg ~\d:l~tlIfH' gloves to avoid addlng weight. NOTE: All surface areas ".. ·i11 be 90ne in triplicate. 2. Add samples to weighIng cans. 3. Dry samples Over P20~ ,n e\Jcu.1ll·d dcsiu':JIOr until \\'eishts Jrt: (On'd"iant (dry \\'tl and record as ~ 4 Add approAimatcly 3ml of EGME to each 5. Set sample In desiccator 0\ pr Jrohvdrous CaCI: anc: Jllow !O t'qudhrJt(· 10: 30 min. 6, Evacuate desiccator for 45 min., turn off the v.lccurr" ,lnd allo".... to set iar about 6 hours. 7. Rc\velgh the samples 8 Return sample to desiccator, fe-evacuate for 4S nlln and alin\.... to 51: over nigh:. 9 R('weigh the samples. 10 Comrare weIghts tor con<:'lqiinCV ;mn r{'cord. NOTE: ThIS welgrllng rrocf'dure should be oon(' until wt'l!-:'hts are c.on~lst('nt or PI rors mdV result in calcu/alln!! surface areas. 11. Obtain the .1rl~orb;I1p WCI~hl Irom the t'quilibrlum we,~hl rned,>",Hcd In qct' 10 minus the samrll' \.... t·l~hl nlt'a~ur('d In step 3 above. CALCULA TlONS Surf .. cc Areds 1. Calculate surface area of sample (SA) uSIng the follOWing equation: grams oi .1c1s.orb.lt{· rn~ SA in m'/g = ----- ~rams or s.lmple O,OOO~86S NOTE: Errors may result if all the H 20 wa~ nOI removed or the [C.\.1E \\.)1, not al equiliurium IlEfll!fNCES H"IIm.ln. M.D. cui. "The Ethl'lcne Glycol Monocthvl Edwr (fGME I: T (', hn'qu(> for D('terminin~ Soil Surface Area." Soil Scit.'ncc. 100(61: .. W9-413 D.2.2 APPENDIX D, PART 3 . Adsorption of Gases in Multimolecular Layers By STEPHBN BRUNAUBR, P. H. EMMETT AND EDWARD TELLER Introduction I •.The Polarization Theory of DeBoer The adsorption isotherms of gases at tempera and Zwicker tures not far removed from thm condensation According to DeBoer and Zwicker, the induced points show ,two regions for most adsorbents: dipole in the ith layer polarizes the i + 1st at low pressures the isotherms are concave, at layer, thus giving rise to induced dipole moments higher pressures convex toward the pressure axis. and binding energies that. decrease exponentially The higher pressure convex portion has been with the number of layers. If we call the dipole variously interpreted. By some it has been moment of a molecule in the'i-th layer Ill, it attributed to condensation in the capillaries of follows that the adsorbent. on the assumption that in capil -.jIo( - c,O (1) laries of molecular dimensions condensation can where C, and C are appropriate constants, C actu occur at pressures far below the vapor pressure of ally being equal' to 1lI/1lI- ,. The corresponding the liquid. By others such isotherms are believed binding energy is proportional to the square of the to indicate the formation of multirnolecular ad dipole moment sorbed layers. DeBoer and Zwicker I explained ., - c,C'" (2) the adsorption of non-polar molecules on ionic where eo is another constant. The equilibrium adsorbentS by assuming that the uppennost layer pressure of the nth layer (top layer), P., according of the adsorbent induces dipoles in the first layer to Boltzmann's law varies exponentially wiLh the of adsorbed molecules, which in turn induce binding energy of that layer and, if the only bind dipoles in the next layer and so on until several ing energy were ~at due to polarization, would layers are built up. The isotherm equation which be given by the equation they, and later Bradley,t derived on the basis of p. _ C,e-.·I1Cf' (3) this polarization theory is practically the only It follows, therefore, that quantitative expression that has been so far pro In />. - _..E!.. CO· (4) posed to account for multimolecular adsorption. c, RT However, as we shall show in the first part of this which is identical with DeBoer and Zwicker'S' paper, the polarization of the second layer of equation adsqrbcd gas by the first layer is already much too 1D EaK,' (4a) small to constitute the major portion of the bind 1.;.. - ing energy between the two adsorbed layers, at if C, be replaced by K,Po, -eo/RTby K t , and C' by least in those instances in which the gas molecules K ,. do not possess considerable permanent dipole One can substitute n = fJlfJm , where fJ is Ule vol moments. ume of gas adsorbed at pressure P., and 11... is It seems to us that the same forces that produce Ute volume adsorbed in one complet.e unimolt'cuiar condensation are chiefly respOnsible for the bind layer. DeBoer and Zwicker, I and subsequently ing energy of multimolecular adsorption. On (3) Accvrcliar to DeBoa- aad Zwicka' tbe "" ... -.lue. l ... &11 1.,ft'S, this assumption, in the second part of this paper Deept tbe 6nt _4 the top l.yer, ..tiny tbe equ.ticma jIo( - _I + jIo( +I) (Ia) we shall carry out a derivation of the isotherm .tv.. Squatio. (1) i •• .alutioD ~ (1.~ u equation for multimolecular adsorption by a I - v'r.I--:.u;::' (lb) method that is a generalization of Langmuir's treat C - 2.1: ment of the unimolecular layer. In the third DcBDI:I' and Zwicker ,iYe tbr: apPl'oumatc npre_oa part of the paper we 'shall then apply the isotherm C - .l/(l - .1:') (Ie) Pfluation to a variety of experimental isoUlcnns wb;cb 1... « J Is. rood .pprcni .... Uoa 'or (lb). It obould be 0"'001.. -, • hown',". that wbUli " -< 1 0Ill,. • 'ew 1."en an unaall,. .dlOl'bt-d obtalDed by others and by us on a number o~ &ad. 010" ••••tlOD (Ia) b Dot ..lid 'or the lop I.y.... '0 Ihlo .... catalysts catalyst supports and other adsorbcnts.. ~ .u '" tb...... ,;,,"" out to be ...... oId..... 4 .pproaima.e. D ICoNTltml1TlON PROII THB BURBAU OP CHB>ll5T1lY AND Son.s AND GBORCB WASHINCTON UNIVBRSITY) 0.3.1 310 STBPHEN BRONAUBR, P. H. EMMETI' AND EDWARD TELLER Vol. 60 DeBoer'" in severn! papers showed thal various infinite wave length, and 17" is the gram molecular experimental adsorption isotherms could be fitted volume of the gas divided by Avogadro's number. by equation (4a). However, they could not We shall assume, to start with, that the separa evaluate XI because in all cases, except one, the tion of the argon atoms in the adsorbed state is surface, and tbercCore l7a .. was not known. In about the same as in the solid state_ For a face· the only case where the surface was known' the centered cubic lattice, such as that of solid argon, adsorption proved to be unimolecular in thickness, the distance r between the nearest neighbors is 'and thus the application of the equation would given by the equation not have been justified. ,. - V2D. (6) Bradleyl arrived at an equation identical to where 17. is the molecular volume of the solid (4a) except that K. is taken as unity. Byapply divided by Avogadro's number. It follows from ing it to his data for argon adsorption on copper (5) and (6) that sulfate and aluminum sulfate, and by estimating .. II - 1 D•• 17.. from microscopic measurements of the diame- ,. - 2"'r 0. (7) ters of the adsorbent particles, he evaluated For argon gas at 0° and 760 mm. pressure, n - 1 K" and obtained k values of about 0.6. He con- = 278 X to-La and by using the density of solid cluded that the very strong polarization of ad- argon at 40 0 :&:,' one obtains sorbed argon explained the relatively thick ad- a/,' - 0.029 (8) sorption layers (at half of the saturation pressure If we assume that the separation of the argon more than 30 layers) that he believed he was ob- atoms in the adsorbed state is the same as in tht: taining. Emmett and Brunauer1 have already liquid state, air' becomes even smaller. pointed out reasons for believing that the surface The ratio of the induced dipoles in two succes- areas of the s:unples used by Bradley were prob- sive layers is given by the equation ably many times greater than he estimated, and v..+.)/I'< - C - d(a/'~ (9) that therefore his estimate of the thickness of his where d is a constant dependent upon the gco films was high by possibly a factor of 20 or so. It metrical structure of the adsorbed layers and the will now be shown that the ratio of the strength relative orientation of the induced dipoles. If of the dipoles induced in the ith layer to that the adsorbed argon atoms build up in a close· induced in the dipoles of the i-1st layer is of the packing of spheres and the dipoles in one layer order of 0.01 for argon rather than 0.99, a value arc; all oriented in the same direction and per that one obtains from Bradley's k =- 0.615 for pendicu1ar to the surface, then the value calcu aluminwn sulfate. Accordingly the polarization lated for'd becomes -0.35. II The minus sig,j of one layer of argon by the next lower layer is far (8) .. Ia...... tiaad CrItical T.bId.- Vol. VII. p. lL too small to constitute the major portion of the (II) IW4., Vol. I, Po lOa. (10) Th. _ com_.a. of ... electric 1Id4 pood_ at • diotaa.. binding energy between successive adsorbed layers. J3( )1 1 l The estimation of the magnitude of C, the ratio ,b".dlpole .. poioLiaclathudiru:tioal." 1 s.;: So - pi! of the strength of the induced dipoles in two suc- .b.... _, ...01 ... ""'. _nIla.... 01 .b. dipol.... d t1a. pala' .t .bleb '-_ . d . th f u· lbe field i. c:&Icul&led. We take the - di.rect1oQ pcrpeadi.cul&l' to tbe cessive layers, can U'<: carne out lD e 0 OWlDg .ur/ace .... d •• d ...ole by,... boI...... the di.I ...... be..... o .be manner. The field of a dipole 1'1 at a distance r a ...... oDcbbon. TbcoS\-... ,o.. lom.lo.b ... m.I.,....Is ...... d -1 d th d' I • d d for _tOIli' ill luceeuive I.)'IT'II i. vm~ for clOM.pacItiD" 0' .pbc::rea. is proportional to 1'11 T -, an e lpo e, ~, lD uce Tb.... b. 6.101 pntd.eed la .b. ~'.r of •• ,.om '" t1ae itla I.,.... by in a molecule of polarizability a at that distance &II t1a. olber ••om.'" .b... .,. I.yer Is -",2:(1/,') ••b .....b ...... -1 Th • I . .adoD baa to be .steaded O¥U aU lbe otba- ato.. of the ,_,.CI". is proportional to PIa1 r-. e ratio ~ PI 15 The a.ld pnod.eed I. tbe eealer ol.bla ...... tom by &II tb...... therefore proportional to the dimensionless num- t...) 1 ) '" tb. I-Ist ...d I + h. I.yuls \1'<-' + 1'<+. l: (2rl-:r - ::; . her air', and the ratio of the binding energies in r r n. DumericaJ evaluauoo of the fDAolte aum. yielde tbe ...."It. two successive layen to al/rl. -",(11.1/,1) ...01 (,.<_. + .... ,)(8.357-8.823/'1). n, dipole ,,' The polarizability of a gas molecule, a,is given lod.ced Ie .b. '''''m by the •• tII of ,b_ t...,.. Is a . by the equation I'< - ,.1-11.11'< - 0.466 v..-. + I'H') I 2ra - (II - 1)D.. (6) pvia, t .. _/" _ 0.028 the ...w. where n is the index of refraction extrapolated to - I'< _ -0.35; ""-. + 1'<+,) (Cl Dca-. Z. '~Y"~' eM ..... BU. lSC (JGIl). ' (I) DeBoer, "14., BU. HO (UISl). Comp..n.oa wit .. equet.iDII (I.) I. t.b. 'ootDotc to pert 2 .bo," tb.t (I) De_. 4W~ •• BlT, JII (1032). A - 0.36 _/r" ...d ...~ AI < 1. thl:ft'on AI Ia .pproaiaaatc:lr cq"'''' to m a •••11 ..4 an. ••u. ..., T.,. IO'Cf&JIII&L. It, 11.&1 (1011). C. 0.3.2 teb., 1938 ADSORPTION OF CASES 1N MULTIMOLECuLAR LAYERS 311 signiiies that the dipoles in successive layers point for multimolecular layers that is similar to alternately toward the surface and away from the Langmuir's'derivation for unimolecular IIlYcrs. surface. From (8) and (9) we obtain C "" -0.01 The equations obtained appear not only to repre and therefore XI lof equation 4a), or CS (of sent the general sbape of the actual isothenns, equation 4) equals about 1 X 1O~. Hence the but to yield reasonable values for the avcra~ binding energy that can be attributed to polariza heat of adsofl)tion in the first layer and for the tion is negligibly small already in the second volume of gas required to form a unimolccular layer. . . layer on the adsorbents.. In tlie calculation of d it was assumed that In carrying out this derivation we shall let So, the dipbles can. be localized in the centers of the S" S., ... Sit ••• represent the surface aTCll that is atoms, and are 'induced by forces acting at the covered by only 0, I, 2, •.. i, ... layers of ad· centers of the atoms. Furthermore, the calcula sorbed molecules. Since at equilibrium So must tion was made only for the case in wlUch the remain constant the rate of condensation 011 the dipoles in a given layer all point in the same direc bare surface is equal to the rate of evaporation tion and are perpendicular to the surface. Though from the first layer /'. it is realized that for slightly different assump alPs, - lI,si,-6,/ar (IO) tions and for different a.n:angements and orienta where p is the pressure, E,is the heat of aclsorp· tions of the dipoles the value of d will differ from tion of the first layer, and a) and h) are constants. the above, it seems certain that for gases for This is essentinlly Langmuir's equation ior uni· wlUch air' is as small as for argon, the portion molecular adsorption, and involves the Bssump of the binding energy due to polarization forces tion that a" hh· and E, are independent of the operating between the various layers of adsorbed number of adsorbed molecules already prl'sent in gas must be very small. For molecules with the first layer. larger polarizability air' will, of course, be larger At eqUilibrium s) must also remain constant, than for argon. DeBoer chose iodine for his s) can change in four different ways: by con experiments because of its larger polarizability. densation on the bare surface, by l'vaporlltion Even in this case, however, since air' is about 0.1 from the first layer, by condensation on the Ii~t it is unlikely that the energy of binding due to layer, and by evaporation from the second layer. polarization will constitute an appreciable portion We thus obtain of the binding energy of the second layer of ad atps, + b,S,.-6,IH" - 11,.,.-6,1.,. + a,ps, (lla) ~orbed iodine. On the other hand, if the ad· sorbed gas has a large permanent dipole it is where the constants ai, b., and E. Bre similarly possible that many layers may be successively defined to a" b) and E). From (10) and lila) polarized by the mechanism of DeBoer and follows Zwicker. This case has been treated by Braclley.1I (II) It may be well at this point to call attention lhe rate of condensation on top of the f\n;llllycr i!' to the fact that equation (43) in its logarithmic l'tlual to tht· rate of evaporation from the 5C('nnri furm and with K, equal to unity ha.~ btocn used layer.1I 'Extending the same argument to tht· frequently to preSl.'nt adsorption data. Thus a 5l'cond and ('(lllst·('utive layers we obtain plot of log log plpo against \lIe amount adsorbed G,ps. - htl~-··I.r (I :1) has often been found to be linear over a consider 11,,,S'_1I - b,$"-6,,.,.I able range of pip. values. In view of our con clusions relative to the polarization theory it The total surface area of the catalyst is given hy seems that such representations are to be re A-"'\'- s, (l3) garded, for the present, as empirical though - L..."I-o interesting relationships. (12) Bquatioa (11) could !tn'lt heeD arr1nd at 1.I\,"U.\.11 b, .ppl7\ar thc priDdpl. of DLicrocopic ft"nblUt7. L.c:-au .. t~. II. Generalization of Langmuir's Theory number of CyapondoD prOC'nJlCS by ""bleb" dft:n'AMI and .... 1ft. crr.-. 1DlU\ be equal to tbe nUlnlter ot ('oadcaMtioa JIAI<""'''''' lIr to Multimolecular Adsorption which .. lDCI'c.&M" aDd ,. drc:A'ue., h '0110.' •• .., from tbf' •••. priodple t .... t .vuy olber Pf'OCC'l' tbat t:aa occur (Iutla •• , r_ With the help of a few simplifying assumptions eu.ruplc. the aUeliAI on,' of .. JDol«ulc 'rom ODC layer lato _nDlh.l. it is possible to carry out an isotherm derivation will M baJ ••coed b7. ""cnc pt'OC"e .. of cqu~ 'RqUUlq'. Tb ... tIM cqullibriulII, c.~ I. (11), will nat be 'nftu~.ft'd b,. ... rh 'urt"" (II) BnwIIc,., J, e., .... Soc., I7I1t (IV34). po ... 0.3.3 - 312 STBPHRN BItUNAUBlt. P. H. EMW&TT.AND EOWAlUl TBLLBR Vol. 60 and the total volume adsorbed is cut. To make II - CD, wheD P ""' Po. :& must be equal to unity•. Thus from (19) • - .. "~ u, (14) . L...J.-o W,).. r.lII" ~ 1. aDd where "0 is the volume of gas adsorbed on one s - Np. (21) square centimeter of the adsorbent. surlace when Substituting into (26) we obtain the isothenn it is covered with a complete unimolecular layer equation of adsorbed gas. It follow:; that " - -I> (28) ,,- u, num~ of layers that can build up. However, neighborhood of the critical point), whereas on a even if this be the case, the result, equation (B), surface multimalecular layers will form far below may still remain valid. the saturation pressure. This difference is to be . Equation (B) has two important limiting cases, accounted for on the basis of surface' tension con both of which we shall make use of later. When siderations. . In' the gas phase the large free n = I, it reduces to the Langmuir type equation" sw-iace. energy of small clusters makes their (29) and when n ...... (free surface), it reduces to formation improbable. On the other hand, m • equation (A). . Furthermore, it sbould be noted adsorption the "liquid surface" is practicaUy com· that wh.eD % has a smaIl value,· and n is as large plete after the first layer has been adsorbed, so as 4 or 5, equation (A) becomes a very good ap that during the formation of successive layers proximation to (B). To use equation (B), there hardly any surface tension bas to be overcome. fore, one should plot the o:perimental isotherm Application of the Theory of Multimolecular in the low pressure region acrording to the linear m. Adsorption to Experimental Data form of (A), evaluate c and 11.. from the slope and intercept of the straight line, then using these A. S-Shaped Isotherms.-In- several recent ,'Blues in equation (B) solve for the best average papersT.U.11 we have published low temperature value of n. We shall apply this equation also to van der Waals adsorption isotherms for some or all experimental data in the nat section. II of the gases nitrogeD, oxygen, argon, carbon The formation of multimolecular layers on an monOll'ide, carbon dioxide, sulfur dioxide, and adsorbent below the saturation pressure, accord butane on some 30 samples of catalysts, catalyst ing to the present view, is analogous in many supports, and miscellaneous materials, including respects to the formation of .multimolecular various promoted and unpromoted iron synthetic. clusters in a non-ide!ll gas. There is, however, ammonia catalysts, meta1lic copper catalysts, an important difference. In the gas the number pumice, nickel oxide supported on pumice, nickel of multimolecular clusters is negligible compared on pumice, copper sulfate pents.hydrate, anhydrous to the number of single molccuJes (except in the copper sulfate, potassium chloride, crystalline chromium oxide, chromium oxide gel, glaucosil. (IS) P_ tbc -..Ite of C'OlDple~a:I W'C' i.dude hae two otbu _u-.. silica gel, soils and soil colloids, dried powdered 1. If we __.. me lb_t E.. the but of ad!lOl'plioo ID the aet"Oad layer, bacteria, Darco (decolorizing carbon), .and char i • .uD _1M_bat WId' thaa th2 heat 01 llquclac:tioa. eEl - .& - ••• ELl: ..d further &DUme lb •• tile padtiar ia the &.nit layer i. coal. On all of these substances, except charcoal, dilf~Dt ff'Dlll the pack:ial la the hi,ber I.yen, thea tbe ad.,..ptloa typical S-shaped isotherms have been obtained. iMl'tbulD cqoat.iOllIOl'. frn: .urfare bccolEOa the low pr~ portion of the isotherm being ,,_= S & + (6 - &)(2.r - %'2 t ,. - (1 - %) 11 + (, 1)% + (b 1)=' f (C) conca~ to the pressure axis, the higber pressure wbl3'e" _ .... - -VJJf'. &ad' - ••h)/ ..... bue ••Ca) it tlte YolulEO' region convex to the pressure axis, and the inter or .....d __d i.a tJac 6nt I .. ,.•• hea it it CIOmplclel" co¥eRd.. &ad mediate region approximately linear with respect •• i. tJae YOIume •.,horbed i. -lUI,. Wrb_ colEOplde layer. AU the: othEr tC'l"1:a ia lb.. oq•• lioo b ... the ...e 1IIIe.a.aU::., 1M i. (A) .... d to pressure. To these S.shaped isotherms equa (B). It .. to be upccted tbat • i.e Dot "'elY dil'cretlt 're... alt,.. tions (A) and (B) have been applied. Typical Scuila.' - 1. aDd • > 1, cquaUo. (e) pwa • 'Ula" ri.. ia • witll i~. JII"ftMIft tJaaa (16) doea. B •••pI_ 01 tW. b .. a..c. , ....d plots of equation (A) are shown in Fig. 1 for the io lb• ..t~_'" butaao _ .1ia Id <_Ibird pan 01 tID ...._1. adsorption of nitrogen at OO.l°K. on a variety of 2. 1. t.bc: dni... tioD of equau_ (8) ...... "m.d that. "1M tht _a..iID"m InIlDbcr of laycn that caa build up oa &III,. part 01 tbe ad· adsorbents, and in Fig. 2 for the adsorption of .orbial NIf.-e. uloa, .. the apiUaria 01 .. ad.or~at an: laIrly various gases on silica gel. Between relative u.rona i. di.metu. equatJo. (B) CUI dacribe 1M eatirc CXN.II'M of lbe bolba. willi .. lair dcJ1"ft of a.rcurw:J. 11. OD tbe otJau 'b ..d. pressures (PlPo) of 0.05 and 0.35 the plots an tbe- lAse 01 tbe pora 10 aD ab.orbeat waric. roaMda'ably 'rom tbe closely linear. From them the values of v ... and ••epIC. tile: c:xperimcatal poi.... will I.,. bdow the thCOftt:ie&l cunc CIIlaaIatc:d witla tbe hdp 01 jtquatio. CD) at lowc:r prraW'•• , c can be evaluated as explained in the previous &ad .bo.. the: C'Ul"Ve at bI,ber pft.ara. The equatioo ..... Ieb takel section. From c one can obtain an approximate care 01 tJae ..uyiac .... 01 the c:apinaria 18 .value for Et - Ex..u. -_. "." ""'- p - (II + 1).... + ..., •• 1/ " - (1 - %) ~. - 1 6. 1 1 + (, - 1)% - U"+ I 5 (14' Bmmett.. Bru~u ... aod 1..0"«. Soil ScN,,". to bI: publi.'-il"CS. (D) (16) Bruaaua" aad Eauaett. TN. ]OUJlH41., I'r 26&: (lDll). (leS) AClt'af"'U., to equ.uoe. (IT, .nd. (22' -ben •• I. tllc .01... -= or .... ad..,~d i. 0.. C"OlDpl.tC' 6nt I.7U aod 'I ...... , arc tbe 'rw.cUoa. 01 tbe total .w1act De ",hic.b • e _ (lIb.. '.'-.L/n" ...... u.u• ., 1. 2 ...... I Ja,.en CUI bWld up. Ba:auM 01 tbe J.,.~ b,4., .. . .u.ber at coa'ItADU '- equado. (D). lu pnct1caJ UN .. dUliculL From. &.be lI.tun of tJae (D01t..a.GtJ .1. ~. it _d It it ia nidaat that Ho_na-. ' ...... cd,.. cqu.u-. CD) h a ...an7 • !'DOd ..... OUlb .po .,h/h•• .m IMI'l 41ft __1ICla frOID ualty. a.d tt:.udon J!L-at.. pm.'''.O_ I" dncritw 'h~~~l!t;lb" ... wlU bo IJOSI!T lac .. 0.3.5 3314 VoL 60 TAJILB I 6.11 .------r-~_r--~~O VALUlIS OP CoHSTANr.i 1'011 ADSOIU'TlON OP NIT1tOCBII A I - 1 I --r-- o- 6r---~--+---~-~-r---r---r---~ X --:-Ad!lorption oj Ntfrogen iii; . on F. -AlzO, C.r"ly,t 3$. (WI ~ so. 4 f'" ,, I H at 77:J"X_ .. C.n.lonl•• vm " IU.D of 17... and of the volume of gas adsorbed at point straight line connecting the 760·mm. adsorption B on the various isotherms should in general agree point for nitrogen at -183 a with the origin on a closely with each other. Columns 3 and 4 of plot of equation (A) such as is shown in Figs. 1 Table I give a' comparison between the Vm values and 2. is equal to Ilv", with an error of no more and the adsorption volumes corresponding to than 5% on all solid adsorbents with which we " point B for twelve isotherms. It is evident that have worked that gave 50shaped isotherms (enu the agreement is very satisfactory. the two seldom merated at the beginning of this section). This differing by as much as 10%. ' is the same as saying that trlD = vel - PIPo). so The last column of Table I reveals an interest that, for example. trill is 'I, of the volume of gas ing coristancy in the value of the heat of adsorp adsorbed when plPo = II•. tion in the first layer for different adsorbents. TABLE II For nitrogen El - EL is uniformly S40 '" 70 cal. E.-EL VALUES POll DIFPERENT GASRS Since EL is about 1330 cal .• El is therefore 2170 '" N. at A ot Co, at C.HII at 70 C'al. for nitrogen on all twelve adsorbents. Substaacc -183- -183- /' -18- O· AJ,O. promoted Fe At first thought this uniformity may seem rather catalyst 954 894 704 1580 1870 surprising. It must be remembered. however. Silica gel 794 594 1335 1930 that EI is by definition an average heat of ad sorption for the first layer. Furthermore. as is After the value of Vm is obtained from the evident from Figs. I and 2. for PIP. values smaller isotherm. multipliC'ation of the number of mole· than about 0.05 the experimental points do not cules required to form a unimolecular layer by the fallon the linear plot, in othc! words. equation average area occupied by each molecule on tl>e (A) breaks down for the most active points on the surface gives the absolute value of the surfaet.. surface. (The reason for this is probably that area of the adsorbent. In Table III the surface the assumption that EI is independent from the area in square meters per gram has been C'alcu· amount of gas already adsorbed in the first layer. lated from the isotherms of different gases ad· becomes untenable for the most active part of the sorbed on siliC'a gel. using the v... values listed in surface.) Hence Elt as obtained from the linear Column 4. and the cross sectional areas of the plot. must be regarded as the average heat of adsorbed molecules calculated from hoth the adsorption for the less active part of the adsorb· density of the solidified gas and of the liquefied ing surface. gasY It is evident from Columns 5 and G that It is interesting to note that. as shown in Table the areas cakulated from one gas agree approxi· II. the valuc of EI - EL is. approximately con· mately with those calculated from another gas. stant for a giyen gas regardless of the chcmical On the basis of solid·like packing the av~rage surfaC'c area obtained from the seven isotherms is nature of the adsorbent. Thus 011 suC'h different substanc-es as a singly promoted iron synthetic 440 squarc meters per gram of silica gel. and the ammonia C'alalyst and silic-a gel. the values of maximum deviation from the average is 15%; EI - EL are for nitrogen SW ... 50 cal .• for argon on the basis of liquid-like packing the average 650 ... 55, cal.• for carcon dioxide 1460 ... 120 surface is 500 square meters per gram. and the caL. and for butane 1900 ... 30 cal. Furthermore. maximum deviation is 10%. In Table III. as is evident from Figs. 1 and 2. the values of the Column 7. is listed the value of adsorption at interc-epts. l/t.... c. are small i~ all C'ases. The Point B on the seven adsorption isotherms. It consequence of these facts is that a single adsorp. will be seen that for six isotherms the agreement tion point for any gas for which an approximate between v ... and the volume at Point B is very value of E" -: EL is ·knoWn will enable one to fix " ... good. but for butane the fonner is twice as large within romparatively narrow limits for any finely as the latter., For some as yet unknown reason divided solid known to be characterized by 50 the empirical choosing of Point B as correspond· shaped isotherms. For example if the highest ing to a unimolecular layer apparently gives pressure point of Curve 4. Fig. 1. were C'onneCted erroneous results for butane on silica gel. The by a straight lihe to the origin. the slope of the tr .. value. on thC' other hand. as is evident from resulting line (and therefore the value of 17... ) Table III. yields a surface area for the silica gel would differ from that for the curve as now drawn (17) For • table of Ih«M Cl'o. M"CtioaaJ lDollll:wU' ...... aN d~l. of nlcvJ.tioD M'C Bmmett ADd BruDaua-. TIl •• JouaJlA1. by no more tlr,-~~~~ed. the slope of a II, J6~ (1037). D.3.7 316 STEPHEN BRUNAUER. P. H. EIolMSTr AND EDWARD fiLLER Vol. 60 that is consistent with that calculated from the Fig. 3, a value of n (n = 5) fits the data well up other gases. . to a certain relative pressure (PIP. = 0.58), but TABU III at higher relative pressures higher Values of n V ALtTK 0" CoNSTANTS POll ADSORPTION ISOTHERMS ON' give the better fit (n = 7 at pip. ~ 0.72). If one SILICA GaL takes an average value of n = 6, the theoretical Surface: ia -.ta. e..-e.L curve will be in error to the extent of +5% at POi.De. cal. Soti:-£.~·Uid ~ - 0.58, and -7% at ~ = 0.72. On the basis Temp. Cur.c ... pock. pock. B per G.. -c. ~ Fic.~_ ec.I•• lq iDl oc./•• lIIole of the capillary interpretation this means that N. -195.8 6 127.9 477 660 135.3 719 the iron catalyst in question has pores of con· N. -183 3 116.2 434 534 127.0 794 A -183 2 119.3 413 4M 122.0 594 siderably varying diameters. On the other hand, 0. -183 4 125.1 410 477 132.0 586 an adsorption isotherm of oxygen at -183 0 on the CO -183 5 121.2 449 550 132.0 973 adsorbent Granular Darco G (activated carbon), Co. - '18 1 99.0 378 455 102.3 133S could be fitted with a value of n = 2.2 from % = CH" 0 7 58.2 504 504 28.1 1930 0.02 to 0.93, and none of the experimental points At relative pressures in excess of about 0.35 to were off the curve as much as 4%, indicating a 0.50 the plot of experimental data according to rather uniform pore size in this adsorbent. equation (A) deviates with increasing pressures For substances giving S-shaped isotherms n more and more strongly from the straight line. values have been found to range from the low The points deviate in the direction of there being value of 2 for Darco decolorizing carbons to val~es too little adsorption at a given pip. value to of 8 or 9 for some silica gel samples. It is in conform to equation (A). It becomes therefore teresting to note in this connection that for the necessary to use instead equation (B). As already adsorption of butane on silica gel. as shown in explained one can first evaluate c and 17,. by Curve 7, Fig. 2, the higher pressure deviations from applying equation (A) up to plpo = 0.35, and the linear plot are in the direction of too much can then proceed to use these values in equation adsoiption rather than too little adsorption. One (B) to obtain by the method of trial and error would expect just such deviation if the heat of the value of n that gives best agreement with the adsorption in the second layer were still appreci· experimental points. In certain instances, as in ably greater than the beat of liquefaction rather than equal to it, as was assumed in the deriva 500 I I I tions of equations (A) and (B). 11 Adoorption of Nitrogen ond Argon _ In order to be able to calc1Jlate from one iso on F. -AI,O, Col.ly.t ". therm another at a different temperature, one I I M. - so. .. fro. must examine how c, II", and n change with tem· • ,I. " perature. The dependence of c on temperature II., ·"s.,- r:.: v", .1t•. 4ec 'l is exponential since c is approximately equal to ~ '/ ~':~L" .:DT/: ,r.-e.vRT, and E, - EL changes only slightly V II", ~300 with temperature. would be expected to vary !l No .1-/35.6 with temperature owing to the thermal expansion v'"'V -/lDcc of the adsorbed layer as the temperature increases. 1/ / A.I ·,e" _ ,.t4 "[:Y'n-& V· v".."'.3« As a first approximation one may assume that ~ .. £,-Et,.70Dc.1 '":200 ~. /- n-7 17,. changes with temperature as dL II., where /' dL is the density of the liquefied gas. By the same ~ V ./ ,"/ .....- argument n should vary approximately a~ d L VI, ! N, ", _1.3c - ~ W'M·II4.7«. which is, indeed, a very slight variation. It was ::::::::: [,.t,. -'DOul found empirically that the variation in n is ac 100 I~ n-'- ~y tually negligtble. With these assumptions the adsorption isotherms for singly promoted iron catalyst 954 at -195.80 have been calculated from the -183 0 isotherms for nitrogen and argon. o 100 200 300 400 600 600 700 The results are shown in Fig. 4. The a~ent Pre!1'ure, mm. between the calculated curves and the experimen. Fi,.4. tal points appears t,o:~C:fi~~e .. ~,isractory. D.3.8 Feb., 1938 ADSORPTION OF GASES ~YSt~~~U.t.AR LAVSRS 31 j Unfortunately one cannot always safely assume :~~~i~3~~:,!value of 50.6 micromoles of 1/ that II... changes with temperature as dL •• The ;':~~~:pijji,:~l4:&7':E' sample of vitreous silica. change in " ... sometimes may be, considerably ··Th~~~~~~ai;e".\of this same sample was greater, and sometimes less. An. example of the 4690~'~cin\ikcording to Palmer and Clark's former is afford~ by the adsorption isotherms measurem~4'ot:~rate of solution in hydro. of McGavac:k and PatrickII for suHur dioxide on Buorie: acid:,::jl ~ne'~ for the area occupied by silica gel at temperatures between -80 and 40°. one aceio~e,:~~~eciiIc; ;,on::the surface the value In Table IV, Column 2, the " ... values are listed 26.9A.1 (which' is ()btl\ined' from the density of for the six isotherms. It will be noted that "... liquid acetone ~t'25°), one.ob~~s from the above for _BO° is 1.43 times as great as for 40°, whereas II... value a specific -surla~ !lf5540 sq. an., which it should only be 1.15 times as great if " ... would is about 20% larger than Palineiimd Clark's value. have changed as dL 1/1. It is also, to be noted If on the otheiband ~~lDe~seS for the area oc· that in these' isotherms the Et - EL \'1llue de· cupied by an acetbn.e molealle" the value 20.5A.', crellSes markedly with decreasing temperature. obtained by N. Ie A~~ '!or~ici~e~Racked films on water of lo~g-cham' 'Ct.'mpounds· terminating in the CQ-CHa group, one obtains for the specific V ALtIB OJ' CoNSTANTS OF ADSOR.PnON OF SULFtm DIOXInB surface 4290 sq. em., which is about 8% snta/kr ON Sn.ICA GBL (McGAVACIC AND PATlUCIC) than the value of Palmer aIld Clark. These data Temp. _ 4Lo.Eo - XL ELo E. "C. a:../c. a./ce. caI./mole cal.l_ole ca1./mole suffice to show that the agreement is very good, 40 91.6 1.327 1789 4940 6i30 and in our opinion is a weighty confirmation of 30 96.6 1.356 1760 6190 6940 the method that they used for measuring the o 105.8 1.435 1705 5840 7640 -34.4 118.6 1.522 1587 surface of vi treous silica. -54 129.2 1.5i3 1458 B. Adsorption Isotherms on Charcoal -so 131.0 1.642 1364 n - 3.5 for aU sill isotherms. On charcoal, in contrast to all other adsorbents thus far tried by us, no S-shaped isotherms were The experimental data of Bradleyl for argon obtained. The slopes of the isotherms on char· on anhydrous copper sulfate, as well as our own coal decrease continually as the pressure in for this system, II also can be represented satisfac creases, aDd in the neighborhood of saturation torily by equation (B). EJ - EL was found to become practically zero. Such isotherms can be be 745 cal. for Bradley's isotherms, 777 for our fitted with equation (B) if n ~ 1. If we interpret own, n was about 5 for both cases. The surface the limitation in the nWDber of layers that can of our copper sulfate sample was larger; v ... for build up on a surface as due to' capillaries in the Bradley's isotherms was 6.4 X 10-1 mole of adsorbent, then we must conclude that the pores argon per mole of copper sulfate, our \'1llue of or capillaries in charcoal are exceedingly narrow, II... was 10.8 X 10-' mole per mole. It should not more than one or two molecular diameters in, be noted that the value of II.. for Bradley's argon thickness.- isotherm on copper sulfate which we cOnsider to I! n = I, equation (B) reduces to the form be a unimolecular layer was interpreted by Brad· PiP - N"". + Pip. eE) ley as being about 18.5 layers. which is clearly a special form of the Langmuir Recently Palmer and Clarkll published ad equation. In Fig. 5 six isotherms on charcoal sorption isotherms of acetone, benzene, and other are plotted according to equation (E), plv being organic vapors on samples 9f vitreous silica whose taken as ordinate and I' as abscissa. It will be totAl surface area had been measured by com· noted that the plots are accurately linear from paring the initial rate of solution in hydrofluoric 1'/1'0 ~ 0.1 clear up to the saturation pre<~ure. acid of the powdered sample with the rate of Table V shows the constants v ... evaluated from solution of a sample whose area was known. If (20) Puba.,. It i. DOl iatmcd'.UI,. ob.iou. tbat tbe avaporatioD one plots the adsorption isotherms of acetone on ('ODdca •• tioD eqwlibria upreaKd i. cquatioal (10), (11), aDd. (11) tall M .ppli~ to UK' .h«e tbt widtb of .the capillarie... DG't vitreous silica according to equation (A) one ob .Don th •• ODC, two 01' • I ... mol_tow.,. diametCI'L n. priadpl. tains a very good straight line whose slope cor· of aUCI'otC'Opic ,...U'IIibilit,.. bo_e.er, sho •• tlla' thC"M «'quat,;ool ,.au"'o .. &lid "YCD tLou.1a 'b. pr~ 01 dlr.at coodua ..tJoa Ira. (1') )lcCe"a,4 ••d P.lIia. Tw .. Joo.,. .... &1, 'te (UI20). er cyaporalioa iDlo tltc ...·pblUC pl.,. oal,. • Iman pan '0 tbe total (II) P.tlllMl' ••d 0 .... 1r.. P,•• Rrr;r. Soc. (LondoQ). "'''', aao tqulHbrium. n. ejJen of tbe.. aUTO" capUJ..nu wiD .... Dercl, (1035). to .10w do ... Oae atabU.b_nt 01 eq"'Ubri" .. D.3.9 318 IMETT AND EDWARD TELLER Vol. 60 tration, the curves in Fig. 6 for the data of Gold man and Polanyiu on the adsorption of ethyl chloride by charcoal are shown. From the 0° isotherm plotted according to equation (E) values of v .. and c were obtained. Assuming that II... is the same at -15 and 20° as at 0° (since the temperature range is rather narrow), and that c, as before, can I be represented by the exponential "L.-f¥=-+-,,~.,.::r.;"':;~I---+---+-"'~.1,...--1 eEl - EJ./RT, we have calculated the iso- therms for -15.3 and 20°. The cal· culated values are represented by the curves, the poil?-ts are' experimental. Ii Here, as in prev10us instances, equa ~16r--l~~~~~~~~~~~~~~---t--~ tion (E) appears applicable only to E :.: that portion of the isotherm which ..... corresponds to p/Po values greater'than ~ 8r-~~~~~~~---r--~--+---r-~--~ 0.1. In the higher pressure regia,", however (P/Po being between 0.1 and 0.95), the calculated isothermsagrec quite well with the observed points. o 200 400 600 800 For more extended calculation of Pressw-e, mm. the temperature dependence of these FiE. 6. Langmuir-type isothenns it would be molecular cross-sectiorial areas calculated from necessary to make assumptions in regard to the the solid state, and 829 square meters per gram if temperature dependence of II", o~ to detennine II... the molecular areas are calculated from the over a sufficiently wide temperature range to be liquefied gases. The maximum deviation of sur able to estimate it for other temperatures. For face areas from the mean for the seven -- isotherms is about 9% on the basis of solid packing, and 8% on the basis of 6 G··1___ .. 0 -r- 0 liquid packing. Butane adsorption on i , -/5.3': I! charcoal is decidedly smaller (about I o.a._ : -'"-'" 25%) than one would expect on the >i T ~ZO.O· basis of the estimated cross-sectional 1 Y ~ ~-- _L-- area of the butane molecule_ It seems .. " V ~ probable that some of the capillaries ~ ,/ Ati30'pt,on D.3.10 F~b., I !l~8 SVNTII1!5IS' OF l,4·DIMI!TIIYLPIIENANTIIR"NE BY CYCLODlJ:lIVDRATION :MSTlIODS :J19 tions it seems that equation (E) ought to be useful Summary for calculating Langmuir isotherms of van der 1. A critical discussion of the polarization Waals adsorption at one temperature from those theory of multimolecular adsorption is presented. at another. It is shown that the adsorption energy due to attraction of dipoles induced into a non-polar gas TABLE V like argon is insufficient to constitute a major por- VALUBS OP _. FOR ADSORPTION ISOTHERMS ON CHARC:OAL \ tion of the binding energy between adsorbed layers. s.ur... iD oq. a/c. " 2. Derivation of adsorption isotherm equations Tra:ap .. c ...... for multimolecular adsorption are carried out on c .. ·C. i. Fic. 6 .../C. p;;:~i:c ;::f:. N, -195.8 4 181.5 6n 795 the assumption that the same forces that produce -183 1 173.0 646 795 condensation are also responsible for multimolecu- A -195.8 215.5 746 804 tar adsorption. A -183 5 215.5 746 839 3. Numerous applications of the equations are 0, -183 6 234.6 767 894 CO ':183 3 179.5 665 820 given to experimental adsorption isotherms ob- co, 78 2 185.5 707 853 tained by other investigators as well as by us. o 63.0 545 546 WASHINCTON, D. C. RBCBIVBD NOvaMBEIl 19, 1937 -. (CmrnUBIlnON PROl( nm CHENlCAL LABORATOIl1BS OF CoLUMBIA UNIVBR5lTY AND THE CoLLEGB OP THE CrrY 01' NEWYOR.1l:] The Synthesis of l,4-Dimethylphenanthrene by Cyclodehydration Methods By DOMENICK PAPA, DAVID PERLMAN AND MARSTON T. BOCItRT In a recent article, Akin, Stamatoff, and Bo as the final step, and in both cases obtained a gertl reported the synthesis of l,4-dimethylphen dimethylphenanthrene whose properties agreed anthrene from p-x-ylene by the familiar Pschorr with the 1,4- compound of Akin, Stamatoff, and reaction, in which they obtained a product quite Bogert, and without any evidence of the migra different from that secured from the same initial tion of one of the p-xylene methyl groups under material by Bardhan and Sengupta,1 by another the conditions of oUT experiments. Our suggested series of reactions, and to which the latter investi explanation of Bardhan and Sengupta's results, gators assigned the same constitution. therefore, is not supported by this evidence. The experimental results published by Akin, These two syntheses were as shown in the chart. Stamatoff, and Bogert indicated, however, that the Bardhan and Sengupta hydrocarbon was Experimental probably the 1,3-dimethyl isomer, previously pre b.ta-(p-Xylyl)-.thaDol, was pr.p.... ed from bromo-,. reaction. pared by Bogert and Stamatoff, I and by Haworth, "yl..,. aDd ethyl..,. oxide by the Grignard followiDl th. m.thod described by Dr.cul for the I)'D Mavin, and Sheldrick. • thesi. of ,,-huyl alcohol. in a yield of 61 % and a boilinl At the time, it was suggested by Akin. Stamatoff, poiDt of 108-111" at 4 10m. On a redistill.d aamplt, and Bogert, although they could not rearrange the physical coDstaDU wer.: b. p. 105-106' at 3 mm .• their own product to the 1,3-dimethyl isomer by dUo 0.9946. n''D 1.5286, Mo c:aled. 46.30. Mo obsd. selrnium fusion, that perhaps someQ1ing of this 46.48. Bardhan and Sengupta. who .ynthesized it in a differ..,t way, gave the b. p. as llG-U3" at 5 mnl. kind had happened in the final step of the Bard Anpl. Calcd. for C,.H"O: C,79.94; H. 9.39. Found: han and Scngupta synthCllis. We have therefore C. 79.64; H. 9.40. synthesized the 1,4-dimethylphenanthrene by two Ph.nylurethu.-Small whit. roseta of thin na:dl~ slightly different methods, from. p-xylylethyl from petroleum ether, m. p. 79-79.5" (COrT.). cydohexanols, dehydrogenating the resulting Anal. Calc (1) Akja. S.a.atol! and BOI"":. T»U.JOUIU.... I.. I •• 1268 (1031). beta.-(p-Xylyl)-ethyl bromide (I) was obtained from the (2) Banlb,••• d 5o.CUP". J. e..... S""., 2~20 (lV32). abov. alcohol.~nd hydrobromic: acid, a""ordinr to the (I) }101m ..d StalDatotl'. R.6c. ',n. eI...... , II, a&3 (J833). (4) H ..,ort". Mu·in. aod Sbcldrick, J. Cltr",.. Soc., tM (1034). Col) Orc,n'. "Or,anic S,.au.~ ..:· ColI. Vol •. I, IGS2. p. 29t. D.3.11 APPENDIX D, PART 4 EXPERIMENT 36 SURFACE AREA OF AN IRREGULAR SOLID BET Gs.;- Adsorption Method THE BET APPARATUS The surface of an irregular solid or a powder (in this experimer,t silica gel) can be determined from the volume of nitrogen physicaily adsorbed at constant temperature at a series of pressures. The re lationship used is the Brunauer-Emmett-Teller, or BET, equation: v = volume at STP of adsorbed gas P = gas pressure Po = saturation pressure P 1 ('C-l) P vrn = volume of gas at STP needed to v(Po - p) = vmC + vmC Po form an adsorbed monolayer C = a constant, characteristic of lhe adsorbent-adsorbate pair The sample chamber is cooled with liquid nitrogen. The temperature of the sample chamber is therefore the boiling point of liquid nitrogen at the barometric pressure of the laboratory. The saturation pressure Po is therefore the barometric pressure. From the intercept 'and slope of the graph of p!v(Po - p) versus plpo, C and I'm are obtained and the number of moles of nitrogen required to form a monolayer is calculated. The surface area is then calculated taking the cross-sectional area of the nitrogen molecule to be 12 A2. 429 D.4.1 430 EX PER I M E ~H 3 6 The apparatus (Diagram H) consists of a main gas manifold to which is attached a pumping system, an air inlet. a nitrogen bulb, and a set:ondary manifold made of t:apilIary tubing. To manifold ell : COIIi)rQred Volyme -t=.=:::::==== To mQno~e!er I I ~ (a) (b) OIAGRA~11 H (a) BET apparatu8 with mercury buret. (b) Substitute arrangement, using mercury Ie.. buret. To this secondary manifold is attat:hed a gas buret, a manometer, a sample chamber, and a "calibrated volume," i.e., a bulb whose volume has been previously determined. The volume of each portion of the system must be known, including the space above the mercury in the limb of the manometer connected to the capillary manifold and the" free volume" in the sample chamber. The free volume, also 0.4.2 SUR FA C EAR E A 0 F A SOL I 0 431 called the" dead space," is the volume of that part of the sample chamber not occupied by the sample. It includes any space between sample particles. as well as the space above the sample. All volumes are measured using the procedure described below. Nitrogen and helium are the usual gases used for calibration, although air may also be used. After the system is calibrated (i.e., each volume is measured) the adsorption measurements are made using the pro cedure given below. Nitrogen is admitted to the system containing the adsorbent and the equilibrium pressure is obtained. From the equilibrium pressure and the volumes and temperatures of the several gas spaces the number of moles of gaseous nitroge!l is calculated. The difference between this number and the total number of moles of nitrogen originally present (i.e .. before adsorption occurs) is the number of moles adsorbed at the observed equilibrium pressure. INSTRUCTIONS FOR USE OF THE APPARATU~ Read pp. 89-97 for background material on handling the vacuum system. Test the system for leaks. If there are any, call the instructor. Do not attempt to seal the apparatus by yourself. The mercury reservoirs shown in Diagram H are oper ated with two-way stopcocks connected to a vacuum pump for mer cury removal and to the atmosphere or to a pressure line for addition of more mercury. Most of the gas in the system is in the buret. Keep the thermometer as dose to the buret as possible. Use two hands when turning the stopcocks and turn them with a slight inward pressure to prevent 'Ieakage of air into the system. Be gentle with the stopcocks. Be careful! Mercury propelled by a pressure difference of an atmosphere can smash glass. Protect the pumping system with adequate traps. If a diffusion pump is used, do not start it until the pressure has been reduced to the proper range by the forepump. In addition, do not bring the pressure back up until the diffusion pump has been turned off and its contents allowed to cool. The sample chamber should be made of quartz or Vycor glass. (Why?) The sample should be between 0.25 and 0.30 gm. 0.4.3 432 EX PER I MEN T 3 6 Wear safety glasses at all times and shield the apparatus with a glass safety shield. Vacuum systems sometimes implode, showering sharp glass fragments over the laboratory. For the initial calibration of the system the "calibrated volume" is used. This volume is measured before it is attached to the system, usually by measuring the mass of water or mercury it will contain at a known temperature. ...... OBJECTIVE To determine the surface are per gram of an irregular solid-silica gel or alumina. DIRECTIONS Calibration of the System Volumes The volume of each portion of the system is obtained by admitting gas to it from another chamber whose volume has previously been determined. The ratio of initial gas pressure to final gas pressure is the inverse ratio of the initial and final gas volumes. The final volume of course includes the volume of the previously measured chamber. The procedure is as follows: Fill the calibrated volume with dry air or nitrogen at about atmospheric pressure and record both the pressure and the temperature. Evacuate the rest of the system and shut off the sample chamber and the gas burets. Open the connection between the calibrated volume and the manifold and record the system pressure. Then close off the calibrated volume and admit the gas in the mani fold to each buret bulb successively, recording the new pressure each time. Using the mercury bulb, the mercury '-evel must be lowered to admit gas to a bulb. With the mercuryless buret only the stopcock need be turned. Repeat the procedureith several different values of the initial pressure in the calibrated volume. Calibration of the Free Volume in the Sample Chamber Fill the sample chamber with dry air or nitrogen at about 50 em pressure. Record the pressure, evacuate the buret, and fill each bulb successively with gas from the sample chamber, re cording each new pressure. 0.4.4 SURFACE AREA OF A SOLID 433 Measurement of Adaorption of Nitrogen by the Sample Evacuate the entire system. Shut off the sample chamber and fill the gas buret with nitrogen to a lsuggested) pressure of about 16 cm of mercury. Record the pressure and tem perature. If the mercury buret is used, open the connection be tween the buret and the sample chamber and admit the nitrogen. Immerse the sample chamber as far as possible in liquid nitrogen. Take pressure readings every 5 min until the pressure remains constant for at least 15 min. It usually takes are least ± hr for the system to reach equilibrium. After equilibrium is reached raise the level of the mercury, expelling gas from one bulb. Record the new equilibrium pressure. Repeat untIl the nitrogen has been forced out of the entire buret. If the mercury less buret is used. admit gas from the first bulb into the sample chamber and record the equilibrium pressure. Then close off that bulb and add gas from another bulb, again recording the equilibrium pressure. After all the bulbs have been opened and closed again open and close each bulb to obtain new pressure readings. Repeat until the pressure no longer changes when the bulbs are opened. CALCULATIONS AND GRAPHS Calibration of the Volumes Obtain the volume of the capillary manifold from the several values of the initial pressure in the calibrated bulb and the final pressure in the bulb and capillary manifold. Use Boyle's law in the form Pi = initial pressure Pr = final pressure t· = calibrated volume I'x = volume of the capillary mani fold The manifold volume ('x may be calculated from the results of the different runs and the values then averaged. Alternatively. a graph of ('(Pi - Pr) versus Pr may be plotted, giving a straight line whose slope • is VX D.4.5 434 EXPERIMENT 36 For the volume of the bulbs of the buret use the cal culated value of the initial volume, i.e., that of the calibrated bulb, the capillary manifold, and any buret bulbs previously measured. The same calculations are performed as for the volume of the manifold. For the volume of the dead space repeat the calculation, using as the initial volume the calculated value of L'z and the various buret bulbs. Caiculation of the Volume of Athorbed Nitrogen From the initial volume, pressure, and temperature of the nitrogen calculate the number of moles of gas in the system. From the equilibrium pressure and the volume and temperature in the capillary manifold and in the sample chamber calculate the number of moles of gas present at equilibrium. From the difference calculate the number of moles of adsorbed nitrogen and its volume at STP. Plot the BET graph of p/t"(po-p) versus pipo. Use the barometric pressure for Po. From the graph calculate 1' .. , the volume of a monolayer. The surface area of an adsorbed nitrogen molecule is 2 12 A • Calculate the surface area of the sample. From the known weight of the sample and the cal culated surface area calculate the real area (as opposed to the apparent or geometrical area) per gram. Plot the v versus p isotherm . • . . . • . NOTES The longer the system is degassed before use the more precise and accurate are the results. [f necessary, arrive early and start the vacuum pump so that the system is ready when the laboratory period begins. The mercury le\el should be kept at constant height in the limb connected to the capillary manifold; otherwise the volume of the system will change as the mercury moves up and down. If the arrangement is such that the mercury level cannot be kept constant, the change in the volume of the system must be calculated from the inner diameter of the manometer tube and the position of the mercury meniscus. 0.4.6 SURFACE AREA OF A SOLID 435 If the initial l6-cm pressure is not suitable, use a different starting pressure. Trial and error determine the optimum conditions. The measured volumes should be precise to within 5 percent. E\ ,,"y time a new volume is determined by pressure change, the smaller the initlal volume the greater will be the pressure change and the more precise the calculated result. The mercuryless gas buret has an advantage in that more points may be obtained on the volume-pressure adsorption iso therm. Each bulb is closed off after being opened, and so the four have different pressures after each one of them has been opened. QUESTIONS 1. State the assumptions. explicit and implicit, of the BET equation. Comment on their validity. 2. What error, if any, results from the presence of ! percent of oxygen in the tank nitrogen? How could the oxygen be removed? 3. On silica gel the results of surface area determina tions with nitrogen, neon, helium, and carbon monoxide agree with each other but disagree with the results with butane and pentane, which are considerably lower. Explain. 4. Look up the thermal coefficients of cubical expan sion of quartz and of Pyrex. Calculate the change in dead space on cooling a Pyrex and a quartz sample chamber from room temperature to the nitrogen boiling point. REFERENCES . 1. Brunauer, S., "The Adsorption of Gases and Vapors," Vol. l. Princeton Univ. Press, Princeton, New Jersey, 1943. 2. Brunauer, S., Emmett, P. H., and Teller, E., J. Am. Chern. Soc. 60, 309 (1938). D.4.7 APPENDIX E PROPOSED ASPHALT EMULSION COLD MIX DESIGN METHOD (Modification of the Marshall Method, ASTM D-1559-82) APPENDIX E PROPOSED ASPHALT EMULSION COLD MIX DESIGN METHOD (Modification of the Marshall Method. ASTM D-1559-82) 4.2 Preparation of Aggregate --- Use standard practice for sampling aggregates. ASTM D-75-82, as applicable. Use Job Aggregates at average room temperature Determine moisture content of aggregate 4.3 Determination of mixing and compaction temperatures --- Mixing and compaction shall be done at prevailing room temperatures • Mix components.. and mix and compaction equipment shall be at prevailing room temperature. 4.4 Preparation of mixtures Weigh into separate pans for each test specimen the amount of aggre gate required to produce a batch that viII result in a compacted specimen 2.5~ 0.05 in. in height (about 1200 g.). Add amount of aggregate pre-vetting vater required - as determined in the "Emulsified Asphalt/Job Aggregate Cold Mix Test." Mix the aggregate and vater rapidly and thoroughly until surfaces subjectively appear to be settled. Add amount of asphalt emulsion required ad determined in the "Emulsified Asphalt/Job Aggregate Cold Mix Test." Immediately mix vetted aggregate and emulsion vigorously scraping sides and bottom ·of container for 15-120 seconds or until maximum coating has been attained~ 4.5 Compaction of SpeCimens Immediately after mixing aggregate. vater and emulsion. place cixture in mold and rod or spade around and through mixture several times to assure uniformity of the mix in the mold. Remove collar and smooth surface of mix to a slightly rounded shape. Replace collar. place mold assembly on the compaction pedestal in the mold holder and apply 30 blows of the compaction hammer to each side of the specimen. An automatic compaction hammer device is satisfac- tory. E.1 Place fitted filter paper on both, ends of specimen. Allow compacted mixture to cure in mold at room temperature for 16-18 hours on wire grid. Place mold containing compacted mixture on wire grid in a forced-air oven for 48 hours at 140· F. I=ediately from oven, while hot" recompact specimen with three 40,000 pound double-plunger static loads using a 30 second relaxation period between applied loads. Remove specimen from mold and allow to cool to room temperature. Weigh, measure and test specimen according to ASTM D-1559-82 "proce -- dure". .. Note: ~~en using the kneading compactor, 50 blows of the compacting foot at the 3.4 MFA (500 psi) mode is sufficient for initial compaction. Follow the same procedure for specimen curing and recompaction as outlined above. Heating of mix, components and equip~ent is not required. E.2 APPENDIX F ALASKA FROST HEAVE TEST EQUIPMENT AND PROCEDURES INTRODUCTION This summarizes current (1982) equipment and procedures used for the frost heave testing of soils by the Research Laboratory, Alaska Department of Transportation and Public Facilities. This procedure is an evolution from previous test methods. The design of the testing apparatus was conceived to create an environment thought to produce the worst possible situation, i.e., unidirectional freezing of samples from the top down, with an unlimited water supply located at the sample base. This testing procedure does not necessarily duplicate any field situation. EQUIPMENT The equipment included: A modified Gibson vertical freezer, ring molds, dial guages, thermometers, surcharge weights, split concrete cylinder mold, a Kango Model (638) vibratory compaction hammer or equivalent, scales, and other miscellaneous standard lab equipment. The freezer used is a standard home upright model modified to create a unidirectional freezing environment. The interior is divided into two chambers by an aluminum watertight pan. The pan is approximately 6-inches deep, made from O.25-inch stock, and is fitted across the midsection of the freezer such that heat flow is primarily upward through the samples being tested. A detail of the heave cabinet is shown by Figure F-1. The pan is linked directly to the outside of the freezer so that water level and temperature can be monitored and adjusted if necessary. The freezing coils are contained in the upper chamber of the freezer cabinet. Stratification of the air in the two chambers is avoided through the utilization of small fans for continual mixing. The fan in the upper chamber moves the air downward through the freezing coils. F.l Four holes are located in the top of the upper chamber to permit ex ternal heave measurement of four heave samples contained in the pan between the chambers. The lower chamber below the aluminum pan is insulated from the outside and bottom cooling coil with polystyrene insulation. The interior of the chamber is maintained at 40°F with two 60-watt light bulbs, and the air is circulated with a small fan mounted on the back wall. The temperature of each chamber is controlled through a separate thermostat. The thermostat for the upper chamber is connected to the freezer refrigeration unit and acts to cool the entire cabinet. The other thermostat acts in turning on and off the heat source below the pan in the lower chamber. To allow brief viewing of samples during testing, without substan tial heat loss, a piece of clear plexiglass is mounted inside the door of the freezer. The inside of the door is modified with a plywood cover to replace the original plastic door-liner and molded shelves. To effect a tight door seal, clasps have been added for a positive closure. Indoor-outdoor thermometers are mounted on the outside of the freezer cabinet to allow for checking the different chamber temperature. The ring molds are cut from a clear acrylic plastic buting having an approximate outside diameter of 6-inches and an liS-inch wall thick- ness. Two ring heights are used for the testing. An 0.5-inch ring is used at the top followed by five 1.0-inch>rings. The heave dial indica- tors used are graduated to 0.001 inch, with faces of 3-inch diameter. Rods are placed through the top of the freezer to contact the sample and be in contact with the dial gauge. This linkage allows for external reading of movement inside the chamber. The surcharge plates placed on top of the samples are constructed of lead and aluminum, and provide an effective surcharge of 0.2 psi, approximately the weight of 2.5 inches of asphalt pavement. A modified split concrete cylinder mold is used to contain the sample and prevent breakage of the plastic rings during compaction of the sample prior to testing. The split mold is fastened together during compaction with bolts and wing nuts, and will spring apart sufficiently on release to permit easy removal of the compact sample. F.2 Testing Procedures 1. Obtain a minimum of 25 pounds of material of the approximate gradation desired for each heave sample to be tested. 2. Mechanically separate the material into the sizes desired for later recombination into test samples (unless the test is to be made on the as-received gradation), and remove the + 3/4-inch fraction which is normally not included in the test sample. Save all No. 200 material. 3. Wash the material first by rinsing each fraction thoroughly on the sieves on which they were retained. Each size is then placed in a large pan and flushed until the water is clear, and next drained. Each fraction is hand agitated with only the water that remains in its large pan after draining. Then each fraction is again flushed and drained to assure that all fractions are free of No. 200 parti cles and to permit accurate control by measuring and adding this size fraction during the mixing of the test samples. 4. Dry all fractions in an oven and allow them to cool to room temper ature. 5. Weigh the materials, each gradation separately to 0.1 g, and combine them to the desired gradation for testing. Place them in a sealable container for mixing. 6. Dry mix the material until all segregation is eliminated. 7. Add a measured amount of water to attain optimum moisture as predetermined by AASHTO T-180 D maximum density testing. 8. Seal the mixing container and thoroughly agitate to disperse the water equally throughout the sample. 9. The split mold is fitted with one 0.5-inch high plastic ring on the bottom and five 1.0-inch high plastic rings and mounted on a standard base plate. The whole apparatus is then weighed. F.3 10. The material is then placed within the rings in three lifts of approximately 1700 grams each. Each lift is compacted with a vibratory hammer until well seated in the mold with approximately 95% maximum density. Scarify between lifts to eliminate segre gation of the layers. 11. The whole apparatus, including the compacted sample, is then weighed. The weight of the sample is calculated and the density determined. If the desired density, usually 95 to 100% of the AASHTO T-1BO 0 maximum density, is not achieved, the sample is removed and recompacted using shorter or longer compaction times. 12. The split mold holder is removed from the sample and a porous stone is placed on the upper end of the sample. 13. The sample is inverted so the porous stone is on the bottom and is then placed in the pan within the test chamber. In this final test position, the 1/2-inch high ring will be at the top of the sample. 14. The surcharge weights are placed upon the samples. 15. The pan is filled with water at a temperature of approximately 40°F to within 0.25-inch of the tops of the samples, and left to soak for at least sixteen hours at a temperature of 40°F. 16. The water is drained to within 0.25 inch above the bottoms of the samples, and a metal baffle plate inserted to separate the water from the insulation surrounding the samples. 17. The pan containing the samples is filled with polystyrene insu lation beads to the level of the bottom of the surcharge weights. lB. The dial guages are linked to the top of the surcharge plates and the temperature is set at 15°F for the upper chamber and 40°F for the lower chamber. 19. Measurements of the heave of the sample are recorded on an hourly basis during work days for a 72 hour period. An automated heave recording system may also be used to obtain the heave data. 20. The samples are removed, measured for total height, and separated at the frozen/non-frozen interface. F.4 21. Depth of freeze is measured from the top of the samples. 22. After removal from the rings, the upper (frozen) and the lower (thawed) parts of the samples are placed in separate pre-weighed pans, weighed, and oven-dried to establish the final moisture content. 23. Washed gradations are run on each heave test sample to verify the actual grading tested. 24. Heave rates are calculated from the data obtained using the average heave rate for the time period between 48 and 72 hours after the start of freezing. This summary is not intended to be a complete description of all of the equipment and procedures involved in the Alaska frost heave testing. Additional information may be obtained by contacting: Department of Transportation and Public Facilities Division of Planning and Programming Research Section 2301 Peger Road Fairbanks, AK 99701-6394 Telephone: (907) 479-2241 F.5 Circulating Fan Water Lovel ...... Indicator Po,ou./ B_NI Slone ~~CUIaIl"9 -1£ Light Bulb ~_I." :::~::. Lower Chamber .:::?::::::,:{:::}::::;.;:::}::::::::y:::=::;:::),.:: .. :.::. ::}:::::::::::,::::::::::::::-:::::::::;,::::::;.::: .. :.:. .":.:.::.:.;':.:.: ~{<{:)::::: .!::;:: INTERIOR DIAGRAM OF HEAVE TEST CABINET F.6 APPENDIX F ALASKA FROST HEAVE TEST EQUIPMENT AND PROCEDURES