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~F~L STABILIZATION for RENOTE AIRFIELDS ~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.
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