REPORT OF INVESTIGATIONS/1989

Backfill Properties of Total Tailings

By C. M. K. Boldt, P. C. McWilliams, and L. A. Atkins

BUREAU OF MINES

UNITED STATES DEPARTMENT OF THE INTERIOR Mission: As the Nation's principal conservation agency, the Departmentofthe Interior has respon­ sibility for most of our nationally-owned public lands and natural and cultural resources. This includes fostering wise use of our land and water resources, protecting our fish and wildlife, pre­ serving the environmental and cultural values of our national parks and historical places, and pro­ viding for the enjoyment of life through outdoor recreation. The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also promotes the goals of the Take Pride in America campaign by encouraging stewardship and citizen responsibil· ity for the public lands and promoting citizen par­ ticipation in their care. The Department also has a major responsibility for American Indian reser­ vation communities and for people who live in Island Territories under U.S. Administration. Report of Investigations 9243

Backfill Properties of Total Tailings

By C. M. K. Boldt, P. C. McWilliams, and L. A. Atkins

UNITED STATES DEPARTMENT OF THE INTERIOR Manuel J. Lujan, Jr., Secretary

BUREAU OF MINES T S Ary, Director CONTENTS Page

Abstract...... 1 Introduction ...... 2 Test procedure ...... 2 Mix composition...... 2 Mix handling ...... 4 Laboratory testing ...... 4 Test analysis...... 4 Laboratory tests ...... 4 Statistical analysis ...... 5 Discussion of results ...... 9 Summary...... 11 References ...... 12 Appendix A.-Mix matrix and test results ...... 13 Appendix B.-Statistical definitions for goodness-of-fit ...... 17 Appendix C.-Linear regression results for tailings A ...... 18 Appendix D.-Mathematical representations and indices of determination for exponential curves relating compressive strength to water-to-cement ratio...... 21

ILLUSTRATIONS

1. Grain-size gradation curves for tailings A, B, and C ...... 3 2. Grain-size gradation curves for pit-run smelter slag, ground smelter slag, and oil shale retorted waste. . . 3 3. Seven-day compressive strength versus water-to-cement ratio for tailings A ...... 7 4. Compressive strengths versus water-to-cement ratio for total tailings data base ...... 8 5. Compressive strengths versus water-la-cement ratio for tailings A, B, and C ...... 8 6. Compressive strengths versus water-to-cement ratio for tailings A, B, and C (not containing additives) .. 9 7. Seven-day compressive strength versus 28-, 120-, lBO-day compressive strengths, and 28-day tensile strength for tailings A, B, and C ...... 10 8. Seven-day compressive strength versus 28-, 120-. 180-day compressive strengths, and 28-day tensile strength for tailings A, B, and C (not containing additives) ...... 11

TABLES

1. Slag chemical analysis ...... 4 2. Linear correlation coefficients for tailings A variables ...... 6 3. Comparisons of goodness-of-fit for tailings A data ...... 7 UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT m inch pct percent

IbjW pound per cubic foot psi pound per square inch m2jkg square meter per kilogram stjh short ton per hour min minute wt pct weight percent mm millimeter BACKFILL PROPERTIES OF TOTAL TAILINGS

By C. M. K. Boldt,1 P. C. McWilliams,2 and L. A. Atkins3

ABSTRACT

This U.S. Bureau of Mines report presents a study of three typical tailings samples as potential cemented backfUl in underground mines. The testing series was unique in that the pulp densities of the samples were all above 75 pct solids. Test results included dry density; slump; percent settling after 28 days of curing; tensile strength after 28, 120, and 180 days of curing; and unconfined compressive strengths after 7, 28, 120, and 180 days of curing. The physical properties of the various test mixtures were further analyzed using linear and nonlinear statistical methods to produce correlations and mathematical equations. Physical properties were used to determine the influence of mix additives and as input for numerical modeling studies of backfill. The mathematical relations were used as a predictive tool in determining the suitability of various materials as backfill.

lCivil engineer. 2Mathematical statistician. 3Engineering technician. Spokane Research Center, U.S. Bureau of Mines, Spokane, WA. 2

INTRODUCTION

Conventional room-and-pillar mining has been com­ water content, the backftll needed to be designed for high monly used in the United States. However, the domestic permeability where the excess water was drained and mining industry has been hardpressed to maximize mineral pumped out of the mine. Bleeding of the cement and productivity in order to compete with foreign suppliers. aggregate fines through the drainage water was a common As a consequence, U.S. mines no longer have the luxury of problem, resulting in greatly varied in-place strength. leaving ore-rich pillars as ground support, and reserves Today, pumps and pneumatic blowers are capable of tied up in highly fractured material cannot be left behind. handling a mine's rugged environmental requirements Existing mines are also encountering greater ground while meeting a 100-st/h operating speed. These new stresses as mining progresses deeper, causing the openings pumps and pneumatic stowers may make it favorable to to squeeze inward dramatically or suddenly burst. In transport >80 pct solids, total tailingsS material from the certain regions of the country and particularly near urban mill to the stope for use as backfill. This capability no areas, ground subsidence poses safety and environmental longer limits the mix matrix to 70 pct solids or to the in­ hazards. clusion of only the sands fraction of mill tailings. The Backfilling stopes allows removal of pillars in addition resulting decrease in water improves the strength, homo­ to controlling ground subsidence. The fill also acts as a geneity, and curing time of the material, and makes lean, medium with established engineering properties and pre­ cemented total tailings backfill an attractive option. dictable behavior. These advantages can allow mines to This report summarizes laboratory work done by the maximize their ore reserves. Bureau to define the strength characteristics of lean, Backfill has been extensively used worldwide. The cemented backfill using total tailings as aggregate, and Bureau was involved as far back as 1964 in defining the varying the cement and other additives as well as the water properties of hydraulically placed backfill (1).4 From 1961 content. The mix matrix used simulated the higher pulp to 1970, Canadian researchers tested a multitude of mixes densities capable of being transported and placed by large utilizing portland cement and mine tailings (2). These concrete pumps, physical stowing equipment, pneumatic tests all used the common mode of hydraulic transport of blowers, or gravity free fall. materials that were typically <70 pct solids. At 45 pct

TEST PROCEDURE

MIX COMPOSITION Construction Technology Laboratories of Skokie, IL (5). The chemical analysis is shown in table 1. Since the The mill total tailings used as the basic aggregate in this hydraulicity, or the ability of the slag to react with water, test series came from three underground metal mines: is believed to increase when the slag is ground very fine Tailings A from a deep silver mine in Idaho, tailings B (6), the tests included different gradations of ground slag. from a lead-zinc mine in Missouri, and tailings C from a Slag samples of 400,500, and 600 m2/kg as determined by copper-silver mine in Montana. Grain-size gradation the Blaine test (7) were mixed with water and showed no curves are shown in figure 1. The fines content of the unconfined compressive strengths through 28 days of total tailings was retained to minimize the void ratio. This curing time because the material remained in the original practice has been documented as improving strengths and slurry state. Grain-size analyses of the pit-run and ground decreasing fill consolidation (3). Mix matrices are summa­ smelter slag are shown in figure 2. rized in appendix A. 3. Oil Shale Retorted Waste.-Because previous oil Commercially available Type I and II portland cement shale research had documented the cementing properties and tap water were used in all mixes in the test series. of certain retorted wastes (8), oil shale retorted waste was The following additives were incorporated in the test mixes used as an additive to determine if its cementing proper­ to determine their influence on some of the physical prop­ ties could be used in the backfill. The grain-size gradation erties of the tailings. curve of the retorted waste is given in figure 2. 1. Fly Ash.-Various mixtures of commercially available 4. Kiln Dust.-A locally available source of kiln dust ASTM Class F fly ash (4) were added to the tailings to was used in a few mixes to determine its cementitious determine whether the pozzolanic influence would be suf­ effects. ficient to decrease the required amount of cement and still 5. Superplasticizer.-An ASTM Category B superplas­ maintain the unconfined compressive strength. ticizer (9) was added to a few mixes to determine its abil­ 2. Pit-Run and Ground Smelter Slag.-The cementing ity to decrease the amount of water necessary to initiate innuence of the smelter slag was determined by cementing action and maintain pumpability. Ten times the

4ltalic numbers in parentheses refer 10 items in the list of references 5fotal tailings, as used in this report, includes the full range of mine preceding the appendixes at the end of this report. tailings, typically from 0.001 to 6.0 mm in diameter. 3

SCREEN ANALYSIS SEDIGRAPH-5000 ANALYSIS u.s. standard sieve size 30 40 7080100 140 200 100 o r"1'-- 1'-", 1'- ...... KEY 90 1'-." 10 , -- Tailings A .r::. .r::. r-...... -- Tailings B OJ OJ 80 20 "- _.- Tailings C Cll Cll "'" '\ '-. 3: 3: 70 \ " 30 >- "1\ .c 60 \ 40 Cll (/) Cll ~ \ c: 50 50 co ~ "" o '" u 40 60 I- Z "'. ~i'- I­ '\ W 30 ~ 70 Z 0 '. W 0: 'I'\. o 20 ~ W '" 80 0: a...... W " a... 10 ...... "" ------90 r- ...... 0 ----...... I- -- 1 00 0.50.4 0.3 0.2 0.1 0.01 ---- 0.001 GRAIN SIZE, mm

Figure 1.-Grain-size gradation curves for tailings A, B, and C.

co Gravel Sand Fin e s ,0 Silt (nonplastic) 0 '" Coarse I Fine Coarse Medium I Fin e CJ '" to clay (plastic) U.S. standard s i e ve s i z e 6 3 1-1/23/4 3/8 4 10 16 30 50 100 200 100 .,- 0 r'\r\ KEY 90 r~ 1 0 """ "\' \ -- Ground smelter slag .r::.- .r::. ~ \ -- Oil s h a Ie ret or t OJ OJ 80 20 \ _.- Pit-run smelter slag Cll OJ 3: 3: 70 r--. 30 >- >- .c .c 60 \ 40 i' Cll \ (/) OJ ...... c: 50 50 co ...... 0 1\ u I- 40 .... , 60 Z I- W 30 1\ 70 Z 0 W 0: \ " 0 1\ '\ W 20 80 0: a... \ W \ a... 10 ...... 90 i'-._. -...... -... 1'\ 0 ", 100 100 10 1 0.1 0.01 0.001 GRAIN SIZE, mm

Figure 2.-Grain-size gradation curves for pit-run smelter slag, ground smelter slag, and oil shale retorted waste. 4

manufacturer's recommended dosage rate for concrete was moist curing. Each strength test was run on a duplicate needed before a measurable increase in slump was seen. cylinder sample and the two strength readings were aver­ Since results of the. superplasticizer tests were not aged to minimize errors. Eight tailings A cylinder samples promising, no further tests were attempted. were tested: two each for 7-, 28-, and 120-day cured, un­ confined compressive strength tests (12); one for the 120- Table 1.-5Ia9 chemical analysis day cured, confined compressive strength tests; and one for determination of the dry density. Eight tailings Band C Major oxides Concentration, .I2f! samples were tested: two each for 7-, 28-, 120-, and 180- day cured, unconfined compressive strength tests. In addi­ AI 20 3 ....•...... 6.15 tion, the test results of three briquet specimens were aver­ BaO ...... 39 aged to determine 28- and 120-day cured tensile strengths CaO ...... 16.85 for tailings B and C (13). Cr20 3 ...... 05 CuO ...... 06 Initial mixes of the total mill tailings were cast without Fe 20 3 • •....•.•.•. 37.83 benefit of binder (cement, fly ash, etc.). These samples K20 ...... 68 MgO ...... 2.09 remained in it slurry state and did not achieve a MnO ...... 1.81 compressive strength. In addition, the saturated Na~O ...... 5 environment of the fog room prevented any evaporation P20S ...... 01 from taking place. Si02 ··•········· . 30.95 Appendix A summarizes the mix proportions along with TiO~ ...... 37 Zn02 ••••••••.•.• .02 the various additives, the types of tests conducted, and the test results. Cement, fly ash, pit-run smelter slag, ground NOTE.-2.24 pct is accounted for by other smelter slag, kiln dust, and oil shale retorted waste were concentrations or combustion losses. measured as a percentage of the total tailings aggregate MIX HANDLING (dry weight of fly ash plus pit-run smelter slag plus ground smelter slag plus kiln dust divided by dry weight of total The mixing procedure for the test series included use of tailings times 100). The water-to-cement ratio was a portable cement mixer. After the oven-dried total calculated as a proportion of the weight of the water to the tailings material and any additives were mixed for a weight of the cement. The water-to-binder ratio was used minimum of 2 min and visually checked for homogeneity, to determine if the additives influenced the cementing a slump measurement was taken (10). Eight samples were properties of the mix and was calculated as the proportion taken from each test mix, packed into standard 3- by 6-in, of the weight of the water to the combined weight of the waxed cardboard cylinders, and cured in a fog room (11). c~ment, fly ash, kiln dust, and oil shale retorted waste. The slurry density was taken at the time of mixing, and the Because the slag was known as a nonhydraulic additive, it 28-day wet density was measured after 28 days of curing. was not included as a "binder." Gang molds were cast using the various mixes for tailings The slurry density of the mixes was determined by Band C to obtain samples for determining tensile dividing the weight of the solids by the weight of the solids strength. These briquets were also cured in a fog room. and water. Slump measurements were taken to determine possible pumpability of the various mixes and was LABORATORY TESTING measured in inches. The tensile and unconfined compressive strengths (measured in pounds per square The test series included unconfined compressive inch) were averaged through use of replicate testing. strength determinations after 7, 28, 120, and 180 days of

TEST ANALYSIS

LABORA TORY TESTS naphthalene formaldehyde condensate. This type of super­ plasticizer reacts by increasing the charge of the cement Category B superplasticizer did not seem to have an particle, thereby repelling the individual cement particles impact on reducing the water content and increasing the from each other and resulting in better dispersion through­ workability of the mixes. This may have resulted from the out the mix. It also decreases the surface tension of the nature of the superplasticizer used in the tests. The partic­ water, making it "wetter." In these lean mixes «15 pct ular superplasticizer used was Mighty 150,6 a sulphonated cement content), the influence of Category B superplasti­ cizers would be diminished. 6Reference to specific products does not imply endorsement by the U.S. Bureau of Mines. 5

STATISTICAL ANALYSIS appendix B. The results of the linear regression analysis are listed in appendix C. At the beginning of the test series, tailings A results Extreme scatter in some of these data is apparent in the were statistically analyzed to determine if any meaningful itemized predicted variable (predicted Y-value, Fit column) relationships eXisted among the data. Ninety-five sample versus the actual data (7DCOMP column) in appendix C. pairs were cast through the course of testing and included To illustrate, observation 30 of appendix C lists an actual various additives such as pit-run smelter slag, ground 7-day observed strength of 160 psi. However, the pre­ smelter slag, and fly ash. Four candidate predicted vari­ dicted value using the regression equation produced a ables (variables to be predicted from mixture information) result of 343.35 psi. For this reason, two other modeling were measured: average unconfined compressive strength schemes were investigated: a multivariate, linear stepwise at 7-, 28-, and 120-day curing increments and the resulting regression model and a univariate, nonlinear exponential slump value. There were five predictor variables: pit-run model. The differences between these models are de­ smelter slag, ground smelter slag, fly ash, cement, and scribed in reference 15. water-to-cement ratio. The predictor variables were mixed To determine a best multivariate linear model, stepwise in varying proportions to test for fill properties of the regression was applied to the tailings A data. Briefly, this tailings. is a procedure that picks the predictor variables one at a The Minitab statistical computer program was used for time in order of relative importance. This approach has most of the analytic work and the primary statistical two advantages to the user: it produces a linear model to algorithm was a multivariate linear model (14). With 14 represent the data, and in so doing, it searches for the variables involved, it was necessary to perform a preanal­ most important subset of dependent variables that will do ysis of the variables that would sort out some of the more the job. The Bureau's stepwise code has an additional spurious prior to the multivariate model fitting. Therefore, advantage in that it allows the creation of variables that pair-wise correlation coefficients between the variables are derived from the original predictor variable set. For involved were examined first. These values are summa­ example, cement and fly ash content were predictor vari­ rized in table 2 and provide a quick method to determine ables. Terms involving cement or fly ash squared, cubed, which variables are most highly correlated. multiplied, raised to powers, etc., can be easily inserted in The matrix in table 2 is a mixture of both predictor and the model. There is one important aspect, however, which predicted variables, as defined previously. An absolute must be kept in mind when using this model. In forming value of 0.8 correlation coefficient was arbitrarily chosen the regression, the user is always fitting an additive model to delineate significance (a 1.0 correlation coefficient is a of the terms of interest. perfect fit of the line to the data points). Using this crite­ The stepwise procedure was applied individually to each rion, 10 pair-wise relationships were deemed significant; of the predicted variables involved: 7-, 28-, and 120-day however, three of these correlations were between the de­ cured, unconfined compressive strengths and the slump pendent variables themselves, Le., 28-day average uncon­ variable. fined compressive strength (28DCOMP) versus 120-day Mathematical representation of the stepwise regression average unconfined compressive strength (120DCOMP), model is given by with a correlation coefficient of 0.944. Various combinations of variables were further analyzed by least squares fitting (15) a three-dimensional (3-D) hyperplane,? which yielded the following equation: where

7DCOMP :; -73.6 + 32.4 CEMENT - 1.40 W /C Y predicted variable (here, 7-day unconfined strength), where constants found by the stepwise 7DCOMP 7-day unconfined compressive process, strength, psi, and CEMENT cement content, pct, selected predictor variables (cement, and W/C water-to-cement ratio. fly ash, etc.) chosen one at a time in order of importance. The analysis provided an R 2 value of 0.876.8 The various goodness-of-fit parameters r, R2, and I are discussed in It was necessary to use four predictor variables (cement, pit-run smelter slag, water-to-cement, and fly ash), of which only cement and pit-run smelter slag were deemed 'A three-dimensional lincar model. statistically significant, to produce an equation predictin~ Srn all multidimensional analyses. R2 refers to the multivariate the 7-day unconfined compressive strength with an R correlation cocrricien( (appcndix B). value of 0.887 (table 3). Table 2.-Unear correlation coefficients for tailings A variables

CEMENT FLYASH PRSLAG GRSLAG W/C W/B SLUMP SLDEN DRYDEN WETDEN SETTL 7DCOMP 28DCOMP FLYASH ...... 0.106 PRSLAG ...... 260 -0.222 GRSLAG ...... 353 -.170 -0.222 W/C ...... -.873 -.059 -.198 -0.259 W/B ...... -.705 -.572 -.060 -.142 0.758 SLUMP ...... -.336 .232 -.314 -.540 .283 0.057 SLDEN ...... 487 -.099 .561 .477 -.388 -.257 -0.870 DRYDEN ...... 398 -.102 .473 .457 -.548 -.408 -.726 0.820 WETDEN ...... 315 -.519 .557 .353 -.325 -.015 -.603 .653 0.701 SETTL ...... -.274 -.201 -.113 -.081 .143 .253 .334 -.328 -.096 0.001 7DCOMP ...... 939 .168 .165 .325 -.821 -.680 -.346 .456 .432 .288 -0.255 28DCOMP ...... 921 .182 .120 .389 -.781 -.671 -.358 .456 .450 .283 -.254 0.977 120DCOMP ...... 848 .326 .023 .409 -.738 -.697 -.330 .420 .443 .166 -.288 .930 0.944 CEMENT Cement content, percent of tailings. SLDEN Slurry density. FLYASH Fly ash content, percent of tailings. DRYDEN Dry density. PRSLAG Pit-run smelter slag content, percent of tailings. WETDEN Wet density. GRSLAG Ground smelter slag content, percent of tailings. SETTL Percent of settling. W/C Water-to-cement ratio 7DCOMP 7-day compressive strength. W/B Water-to-(cement-pius-flyash) ratio. 28DCOMP 28-day compressive strength. SLUMP Inches of slump. 12ODCOMP 12O-day compressive strength. 7

Table 3.-Comparlsons of goodness-of-fit for tailings A data

Good ness­ Model Mathematical equation of-fit measure 3-D hyperplane 7DAVG = -73.6 + 32.4 CEMENT - 1.40 W IC ... , . , . if = 0.876.

Multivariate, linear stepwise regression 7DAVG = -82.58 + 33.6 CEMENT - 0.74 PRSLAG ... R2 = 0.887.

Nonlinear, exponential. ... , , ... , , . . 7DAVG = 1,515.53e- 0.57 WIC ...... I = 0.889. 7DAVG 7-day cured, unconfined compressive strength. R2 Multivariate correlation coefficient. CEMENT Percent cement in total aggregate contained in mix. PRSLAG Percent pit-run smelter slag contained in mix. WIC Water-to-cement ratio. I Index of determination. Another modeling attempt was made using a two­ Table 3 tabulates the various results of the three sta­ dimensional model with the predicted and predictor tistical methods used to determine goodness-of-fit for the variables fitted by an exponential curve. Figure 3 tailings A test data as applied to predicting the 7-day illustrates the data by plotting the 7-day unconfined unconfined compressive strengths. The 3-D hyperplane compressive strengths to the water-to-cement ratio. This produces a correlation coefficient of 0.876. In the multi­ curve-fit procedure resulted in the following equation: variate, linear stepwise regression model, the anticipated 7-day unconfined compressive strengths fit the observed 7DCOMP = 1,515.53e-0.57 w/c compressive strengths of each test specimen with a corre­ lation coefficient of 0.887. The predictor variables, listed where by order of importance to determine the 7-day compres­ sive strength, are cement and pit-run smelter slag. The 7DCOMP 7-day unconfined compressive nonlinear, exponential model produces an index of deter­ strength, psi, mination (see appendix B for definition) of 0.889, which is quite promising since it is based on only one input vari­ and W/C water-to-cement ratio. able, the water-to-cement ratio. After it was determined that the exponential model would best fit the data curves of the unconfined compres­ sive strengths versus the water-to-cement ratio, the data from tailings A, B; and C were analyzed as a group for comparison. Plots of the compressive strengths versus water-to-cement ratios for the total data base are pre­ I­ sented in figure 4. The mathematical representation of Z 8f-: ill the curves along with their respective indices of determina­ 7 • • tion are given in appendix D. ~ •••• Further analysis of the tailings A, B, and C data ill 6 •••• Uo ,- included exponential curve fitting of the compressive I -5 .... strengths to water-to-cement ratios for the mixes grouped OI­ .- . by tailings type and then by tailings type not containing any l- 4 « Itf._. additives (pit-run smelter slag, ground smelter slag, fly ash, Ie: • I ••• e: 3 • kiln dust, and oil shale retorted waste) (figs. 5-6). The ill · · ,··C... •• mathematical representation of the curves along with their 2 f- • • .~"" I­ • • ..• . • respective indices of determination are also given in « 1 f-- • • • appendix O. ?; As can be seen in appendix D, the goodness-of-fit o 2345678 9 increases as the data base becomes increasingly selective. 7-DA Y COMPRESSIVE For instance, the total data base index of determination, I, STRENGTH, 10 2 psi for 7-day compressive strength is 0.796. For the data base containing only tailings A, I is 0.889; and for the tailings A Figure 3.-Seven-day compressive strength versus data base not containing any additives (pit-run smelter water-to-cement ratio for tailings A. slag, fly ash, etc.), I is 0.982. 8

18 7 -da y 28-d a y 16 ~. ~ • 14 12 •• ... • • 0 10 f- • « 8 .1. • ~ 0: 6 f- z 4 ~. 2 ··n~.M · ,.:.-...... ,. ... -:.: w ••• • • ... . ••• • ~ -r ::?: •• .. .. w 0 2 3 4 5 7 8 9 10 0 2 6 8 10 12 14 16 18 20 () 6 4 I 18 120 -day 180-day 0 16 • • f- I 14 0: W 12 • • f- • « 10 • ~ 8 • • • 6 •., ... e: . • •• ••• • • 4 ... ••• • .- ... .• • • • • • 2 ...... • • . • • .. .. • • .. • 0 3 6 9 12 15 18 21 24 27 30 0 2 3 4 5 6 7 8 9 10 COMPRESSIVE STRENGTH, 10 2 psi

Figure 4.-Compressive strengths versus water-to-cement ratio for total tailings data base.

20 18 7-d a y KEY 28-day 16 -- Tailings A 14 -- Tailings B -'- Tailings C 12 0 10 \ f- 8 « 0: 6 \\ f- 4 ".'-.: Z """ ...... W 2 --- ::?: ------w 0 2 3 4 5 6 7 8 9 10 0 2 4 6 8 10 12 14 16 18 20 () ---- I 20 0 18 120-day 180-day f- ~. I 16 0: w 14 f- \\ « 1 2 \\ ~ 10 \ . 8 \\. 6 ~ "~ 4 '-....~-:-- 2 "~---- . ------'--."'1---- 0 3 6 9 12 15 18 21 24 27 30 0 2 3 4 5 6 7 8 9 10 COMPRESSIVE STRENGTH, 10 2 psi

Figure 5.-Compressive strengths versus water-to-cement ratio for tailings A, B, and C. 9

10 7-da y 28-day 9 KEY 8 -- Tailings A 7 -- Tailings B _.- Tailings C 6 0 5 I- « 4 c: ,,~ 3 ~ I- :--- Z 2 ~---.~- ~. W . ------...... :::::::: - . ~.- - -- ~ - - W '~'- U 0 2 3 4 5 6 7 8 9 10 0 3 6 9 12 15 I 10 I I I I I I I I I 0 120-day 180-day I- 9 I c: 8 ~ w I- 7 - « 6 5: c~\ 5 ,\".~ 4 ~.~ 3 ~":----..... f- 2 ~~~ 1 I ~'--' 0 2 4 6 8 10 1 2 14 16 18 20 0 2 3 4 5 6 7 8 9 10 COMPRESSIVE STRENGTH, 10 2 psi

Figure 6.-Compressive strengths versus water-to-cement ratio for tailings A, 8, and C (not containing additives).

DISCUSSION OF RESULTS

The results indicated that the addition of oil shale re­ The linear relationship (based on least squares fitting) torted waste without the benefit of cement produced com­ between the 7-day compressive strengths and those of 28 , pressive strengths on the order of 100 psi in 28 days. The 120-, and 180-day compressive strengths is presented in cementing properties of the retorted waste were greater figure 7. In each case, the strength gained between each for the finer particles of tailings C. The addition of fly ash pair of relationships was greater as the grain size of the improved the compressive strength of the total tailings tailings material increased. This was just the opposite for aggregate. As the tailings grain size fraction greater than the relationship between the 7-day compressive strength 200 sieve increased, the influence of the fly ash decreased. and the 28-day tensile strength (fig. 7). There was no sig­ The 28-day compressive strength of tailings A was in­ nificant difference in strength gain between the 28-, 120-, creased by 25 pet, tailings B by 48 pet, and tailings C by and 180-day compressive strengths and the 7-day compres­ 98 pet over the compressive strengths gained by the use of sive strength because of grain-size differences (fig. 8). cement alone. However, grain size differences caused a marked differ­ As the grain size of the tailings fraction greater than ence between the 28-day tensile strength and the 7-day 200 sieve decreased, the compressive strengths also de­ compressive strength (fig. 8). The finer-grained tailings C creased for the various curing periods. The 7-day com­ developed a higher tensile strength when compared to the pressive strength for tailings A with 6 pet cement and a 7-day compressive strength. water-to-cement ratio of 4.5:1 was 118 psi; for tailings B The ratios between compressive strength to tensile it was 107 psi; and for tailings C it was 65 psi. strength for the various days of curing ranged from 4.4 for 10

1 0 2 8-d a y 9 B / If) Q. 7 ~/ C\J 6 0 ~ ..... 5 ~ ::r:~ 4 KEY t- 3 o~ (!) ---- Tailings A Z 2 -- Tailings B W a: _0- Tailings C t- OO 0 2 4 6 B 10 12 14 16 1 B 20 0 3 6 9 12 15 1 B 21 24 27 30 W > COMPRESSIVE STRENGTH, 10 2 psi 5 10 r---.---~----.----.----.----.---'r---, 00 1BO-day 2B-day 00 9 W a: 4 B a.. ~ 7 0 3 6 () >- 5 « 2 4 0 3 ,.....I 2

o 1 2 3 4 5 6 7 B 9 10 0 25 50 75 100 125 150 175 200 COMPRESSIVE STRENGTH, 10 2 psi TENSILE STRENGTH, psi

Figure 7. -Seven-day compressive strength versus 28-, 120-, 180-day compressive strengths, and 28-day tensile strength for tailings A, B, and C. the total tailings not containing additives to 4.8 for the x = water-to-cement ratio, total data base. The goodness-of-fit for calculating the compressive and A and B are constants. strengths using the water-to-cement ratio and the exponential formula is This goodness-of-fit progressively improves as the sample groupings become more restricted. Appendix D sum­ Y = Ae-BX, marizes the indices of determination for the various groupings. where Y compressive strength, psi, 11

10 2 8-d a y 120-day 9 8 en c.. 7 N 6 0 T""" 5 - 4 I KEY I- 3 C!) -- Tailings A Z 2 -- Tailings B W a: -,- Tailings C I- (J) 0 3 6 9 12 15 0 3 6 9 12 15 18 W 2 > COMPRESSIVE STRENGTH, 10 psi 1 0 ,- (J) I I I I I I I I I I 180-day 28-da y (J) - ./ w 9 / a: 8 / a.. / ~ 7 / 0 6 - r- / () /"" / ' >- 5 ~ - - - .// « 4 / ' - 0 / I 3 ...... /' /.// 2 /' - /// - ~ t/~' 0 1 2 3 4 5 6 7 8 9 10 0 25 50 75 100 125 150 175 200 COMPRESSIVE STRENGTH, 10 2 psi TENSILE STRENGTH, psi

Figure 8.-Seven-day compressive strength versus 28-,120-, 180-day compressive strengths, and 28-day tensile strength for tailings A, B, and C (not containing additives).

SUMMARY

This series of backfill material testing was initiated to such as those where oil shale retorted waste was added to determine what engineering properties could be expected the tailings, a full range of mixes was not attempted since from a variety of mill total tailings. The incorporation of the problem was merely to determine whether or not the additives was meant to define the extent of increased retorted waste was a detriment to the mix, thereby indicat­ strength or workability of the resultant mix. None of the ing possible uses of oil shale waste. tailings tended to be self-cementing. However, as cement Further research will test the relationships found during contents were increased, compressive strengths increased. this investigative test series. The effects of chemical addi­ The compressive strengths of the fly ash-and-cement com­ tives such as superplasticizers, high-early-strength cements, bination increased after 28 days of curing as compared to water-reducing agents, and kiln dust will be examined. the strength of cement alone after 28 days. The addition With further refinement, an accurate predictive tool will be of pit-run smelter slag, which incorporated coarser parti­ developed that will assist the industry in analyzing the suit­ cles into the mix, seemed to increase compressive strength, ability and stability of dewatered, total-tailings backfill. but the slag alone was not cementitious. In some cases, 12

REFERENCES

1. Nicholson, D. E., and W. R Wayment. Properties of Hydraulic 8. Mareus, D., D. A. Sangrey, and S. A. Miller. Effects of Backfills and Preliminary Vibratory Compaction Tests. BuMines Cementation Process on Spent Shale Stabilization. Min. Eng. (Littleton, RI 6477, 1964, 31 pp. CO), v. 37, 1985, pp. 1225-1232. 2. Weaver, W. S., and R Luka. Laboratory Studies of Cement­ 9. Cement Admixtures Association and the Cement and Concrete Stabilized Mine Tailings. Paper in Research and Mining Applications Association, Joint Working Party. Superplasticizing Admixtures in in Cement Stabilized Backfill (pres. at 72d Annu. Gen. Meet. of Can. Concrete. Jan. 1976, 32 pp. Inst. Min. and Metall., Toronto, Ontario, Apr. 1970). CIM, 1970, 10. American Society for Testing and Materials. Slump of Portland pp.988-1oo1. Cement Concrete. C143-78 in 1986 Annual Book of ASTM Standards: 3. Keren, L., and S. Kainian. Influence of Tailings Particles on Section 4, Volume 04.02, Concrete and Mineral Aggregates. Physical and Mechanical Properties of Fill. Paper in Mining With Philadelphia, PA, 1986, pp. 109-111. Backfill, ed. by S. Granholm (Proc. Int. Symp. on Mining With Backfill, 11. __• Maldng and Curing Concrete Test Specimens in the Lulea, Sweden, June 1983). A. A. Balkema, 1983, pp. 21-29. Laboratory. CI92-81 in 1986 Annual Book of ASTM Standards: 4. American Society for Testing and Materials. Fly Ash and Raw Section 4, Volume 04.02, Concrete and Minerals Aggregates. or Calcined Natural Pozzolan for Use as a Mineral Admixture in Philadelphia, PA, 1986, pp. 142-151. Portland Cement Concrete. C618-85 in 1986 Annual Book of ASTM 12. __. Compressive Strength of Cylindrical Concrete Specimens. Standards: Section 4, Volume 04.02, Concrete and Mineral Aggregate. C39-86 in 1986 Annual Book of ASTM Standards: Section 4, Philadelphia, PA, 1986, pp. 385-388. Volume 04.02, Concrete and Minerals Aggregates. Philadelphia, PA, 5. Weise, C. H. (Construction Technology Laboratories). Report of 1986, pp. 24-29. results, 1984; available upon request from C. M. K. Boldt, BuMines, 13. __. Tensile Strength of Hydraulic Cement Mortars. C190-82 Spokane, WA. in 1984 Annual Book of ASTM Standards: Section 4, Volume 04.01, 6. Nieminen, P., and P. Seppanen. The Use of Blast Furnace Slag Cement; Lime; Gypsum. Philadelphia, PA, 1984, pp. 200-206. and Other By-Products as Binding Agents in Consolidated Backfilling 14. Draper, N., and H. Smith. Applied Regression Analysis. Wiley, at Outokumpu Oy's Mines. Paper in Mining With Backfill, ed. by 1966, 407 pp. S. Granholm (Proc. of Int. Symp. of Mining With Backfill, Lulea, 15. McWilliams, P. C., and D. R Tesarik. Multivariate Analysis Sweden, June 1983). A. A. Balkema, 1983, pp. 49-58. Techniques With Application in Mining. BuMines IC 8782, 1978, 7. American Society for Testing and Materials. Fineness of Portland 40 PP. Cement by Air Permeability Apparatus. C204-84 in 1986 Annual Book of ASI'M Standards: Section 4, Volume 04.01, Cement; Lime; Gypsum. Philadelphia, PA, 1986, pp. 208-215. APPENDIX A.-MIX MATRIX AND TEST RESULTS

W,e Supl. I ~dclli'te .llt,,110g5 .t, pot I wla I Slurry ,I, Orr .1,28-d" SlJop, I! lB-day A, tensIle Wen\th, PSi t\, l!ftCOflt Hied c.OlJlresslV@ str e-nqth, PSl no. Fly , PH ron, Grouoct Kiln 1 OfflSl. tv , ,Cem!ilty, tlet in Settiflent. 7 ~ai 12 , IB'} aa, !C!llerrt 1 retort., 2~ ddr 111Q ca, 116" da, I :Ill ,ay 1 {1 day I ash I slag I slag ,dust 'a,to i .t pet Ilb!!tJ ,ceoslty, ' ~d , i 101ft) I I : I

4.2 76 [ill NA lG5 1" 3.33 J) 102 l! NA NA 211 411 1, 2.7E 2.la 77 100 11 4.~ N~ Nri 218 406 475 14 c.38 2.38 n Ill, ,I • NA NA J4(, j83 4 5.5 5.5 as l.2 1.9 N~ NA 79 99 S9 4 91 l04 L.] M HA 4" &1 91 4 6.5 0.5 so 100 4.7 4.2 NA HA j4 10 3.5 83 m l.' 2.'! Nil NA: m iTt 11 4 B1 lib 4 2.4 NA NA 141 tSO Z6C· 12 4.5 4.5 BO lUI 9.S 3 .• NA NA ue liO 2vb 13 11 2.12 7.43 18 lOb 11 NA N>\ 2S :31 m 14 II 1.86 -1.95 )9 NA II NA NA I~b 170 m 15 11 1,;5 l.71 IS HA 125 11 HA NIl lH 1,6 64b 10 11 11 1. 4~ 2.y! 79 NA 130 11 IIA NA 274 Hl 974 17 13 11 1.:5 2.48 19 113 124 9.2 NA NA 431 701 l1H~ 18 16 11 1.24 2.12 79 i13 124 9.5 NA Nil 4S! diS 1~~~3 19 25 1.1 b.b 8(> lQ7 125 10.5 4.2 NA hA 114 213 336 20 25 1.02 4.4 80 107 122 10 NA NA 159 401 21 l~ 25 C'.94 80 llG 1:4 9.7 1.3 NA NA 25'1 84(, 22 25 a.as 2.M 81 110 125 6 YA NA 4~9 1,380 15 25 0.93 81 113 t1:; 6 NA NA SIB 1,H4 24 lB 25 0.18 1.89 81 114 120 7.5 NA liA ,03 1,024 2,:35 25 o o b. ~7 NA 7b NA UA II NFl NIl H 10 26 7.83 n 101 124 11 NA NA 47 115 5.22 77 104 128 II 1.2 N,\ IIA ~5 ,11 28 3.12 Ii 105 128 11 5.9 NA NA m 1'0 29 11 78 lOb 127 11 NA Nil 183 J8y 30 13 2.61 78 107 128 11 3.3 NA IlA Ibll 38'7 31 14 2.lb 78 llO 133 11 6.b NA liA 3b5 ]b~ Jl o 11 NA 1) 122 m 11 4.l Nil NA (1 49 1: 7.43 7.4: 78 10:, 12:l 11 6. J NA NA 72 166 34 11 4.95 4.95 73 102 126 11 6.2 NA NA 83 35 11 3.71 ~.H ra 103 120 11 6.7 NA NA 13:J 3. Jl 11 2.97 2.97 79 llD 12B 9 4.4 NA NA 30e 31 13 11 o 2.48 2.\3 1~ 110 127 8 4.4 II, IlA m 38 16 II o 2.12 2.12 19 112 tv 9 U NA NA 418 39 33 o •• 25 •• 25 BI 112 114 6 I Nt. NA 19 4C 33 o 4.17 4.11 81 HI 136 5.5 NA NA HI 41 Jl 33 o 3.ll Bl 118 128 4.5 liA HA 295 42 13 Ii 33 o 2.5 2.5 81 115 1.37 5.5 3.5 NA NA 361 43 16 o o 2.02 2.09 82 lib 132 3.7 ~UI NA 44 1~ Ii 33 1. 79 1.79 S2 H8 139 3.2 NA N~ 772 45 8 o 100 4.17 4.17 86 122 141 o 2.5 NH N'; m 46 t2 100 l.lS 2.;S So 121 128 (> N~ NA 27,) 47 Ie 1!)0 2.08 1.1;8 87 l27 ll2 o NA IiA MIX MATRIX AND TEST RESULTS-Continued

WIC Slurr. Drl 2S-C!3\' Sluop. 2,-,,, den:l tv, denSl ;:1, • Et 10 5e~ ~i e!llent • lit ~ct 1tift) !:!!r:Sl tv, p,t lb/ft3

TAILINGS A 100 1.,7 1.,7 87 126 137 4.5 ~A 497 659 100 1. ~9 1. ~9 87 l:':b 13tl 162e' NA 744 1,33~ 100 1.19 1.19 ,7 !2b 139 13 NA 803 1, 7~7 HA NA 122 t;A 11 4.1 13 13 NA 1.B9 6., 80 109 123 ~ 1 53 13 N~ a8 1.65 4.4 80 109 11 13 2.5 HA 154 1. ~7 8(1 11: I'"Lc 55 13 2.a I'A i64 :·27 13 ..... " 81 113 12, 15 13 13 :4i 1.2 81 113 8 7 57 Ie 13 13 1.1 501 ?21 1.89 81 116 8.2 HA 58 13 0.: 357 6~,9 13 1.89 6.6 109 ';I-j 59 \1 NA 13 13 1.,5 4.4 15: 281 liA Bl' 10] 123 11 NH l(: 13 13 NA 80 Ib~ 80 Ill' 122 10.5 ~.::; 61 13 13 NA 233 450 851 1.3: 2.64 81 III 123 10.5 02 is IIA 363 533 1, :65 .IA 1.: 2.: Bl 114 122 10 63 18 13 HA 4~ ~ 782 l.Hq NA 1.1 1.89 81 I1S 1" 7.5 64 11 623 991 1,988 ~A NA 1) NA HA 11 ~M 65 11 NA o o 7.1: 7.43 78 104 125 11 o ~.:. 66 11 NA 71 93 1::'1 4.95 4.75 78 1(15 12, 11 NA 67 , .. HA 1:\ 19, 11 3.71 3.71 78 105 26.3 NA 125 11 1.7 ~A IlA 6S 11 11 2.97 1/9 i.1." 410 I,A 2.97 7' LO] 129 11 2.7 HA 09 13 11 :.48 IIA 377 NA 2.48 79 If.\/J HA 11 3.b HA 70 16 11 2.12 r~A 38(1 IIA 79 lOb NA 11 1.7 Hi1 71 11 HA 6J8 HA B4 liB 134 1.1 72 11 NA NA 130 1" S.S .I • ..l 83 116 p':i NA 3.5 2.1 hA HA NA 11 6 113 130 HA 81 111 128 7.5 N?t 11 NA HA Be l15 .J • .J J • .J 8.1 119 m 2.2 3.8 NA HA 11 NA 215 )01 377 NA 82 114 132 U 76 11 N~ NA 1M 137 20B 4.5 U 80 131 2b6 NA 77 10.~ 2.3 HA MA IIA 103 33 NA HA 80 H" 166 281 HA 127 13} NA 16.8 HA NA NA 7B 6.25 6.25 o o 31 NA Bl 111 133 11 4.5 NA MA 79 33 NA 89 150 249 IIA 4.17 4.17 81 113 135 11 4.3 BO 11 33 HA NA NA 140 218 3.09 3.09 Bl 117 136 365 NA 81 13 3.5 NA NA NA 441 33 2.48 2.48 B2 737 88(' NA 115 134 10 4 NA NA HA 82 16 33 2.06 2.06 325 480 143 HA B2 115 135 9 3.2 NA NA 83 19 33 NA 4b. b24 914 NA 1.77 1.71 B2 117 13b B.l 2.7 84 4 33 HA NA NA bbB 1b6 1,J89 5 B4 121 NA 3.5 4.2 NA II" 85 33 MA NA 10) 138 224 5.5 .J • .J 83 NA NA NA 86 5.7 NA NA NA NA 99 33 6 81 147 220 HA 112 ~A 8.5 3.4 HA NA NA 87 33 3.5 3.5 , , 69 I1b 159 HA 83 liB NA I..:.. 3 NA 88 33 HA NA 14~ 238 371 4 81 115 NA HA 89 3.3 NA NA NA 122 33 4.5 4.5 80 lb8 278 HA NA NA 11 NA ItA NA NA 90 100 4.13 4.13 80 153 195 NA B6 121 140 I.B HA HA 91 12 100 NA 125 179 2b2 NA 2.752.75 87 125 139 1.8 NA 92 16 100 NA NA 21b 357 2.0b 1.06 87 126 110 4B1 HA 93 1.7 NA NA NA 322 20 100 1.b5 1. 65 87 !:2a 698 NA 125 141 2.5 HA NA HA 94 24 100 1.';8 1.38 420 719 1,017 NA 87 123 138 2.7 1.5 95 28 lOu NA KA NA bl0 938 1.18 1.18 B7 123 140 1.J4Z NA 2.B ~A NA NA 824 1,;0(1 1,79 r) HA See ~~pla.rra.tory n!Jt=5 Qt ~nd of taDle. MIX MATRIX AND TEST RESULTS-Continued

S,apl. WiC Slurry no. de",slth ::Ia-nsth! Ifet Itt p~t lb!tt'j

',1 3.9 0.5 30 S.6 J. , B3 j.B E2 128 4.5 4.2 4.~ 4. ~ BO po 10 4.9 2.~ 84 13i 1.5 4.5 '"'255 '., Iv 52 c3 1;3 10 It· as 131 1 113 5~j 764 92: II tv 2.~ 31 lZS b.5 89 107 520 .11 12 10 79 I" 11 4.5 be Bl 2211 360 42! 12 1.0 B4 113 1.75 3.1 13~ 171 ile 1,231 14 82 134 4,25 3.8 122 160 535 l~ 12 2.: 2.5 )9 m II 6.3 98 !lb 325 14 !.~ 1.5 B4 137 1.5 4.2 !~b m "17 ~.O 1.5 1.~ 4.67 Sl !3C 2.~ 4.~ 27 U6 18 4.5 .., .. 4 5.33 82 134 4.5 2. 47 e. 2;:b 19 4.5 4.:: S0 131 10 0.2 '35 Bl 211 2.5 ~4 132 4.2 112 110 200 21 4 ~2 131 5.6 64 13u 123 ,81 n 3.5 ' •• 7 1'1 11 7.3 51 104 29, • 0 23 7.5 " • .J 2.67 85 2 .. , 140 218 756 BBO 24 7.5 2.5 o 3.33 91 3.1 79 lB. 1b2 bl! 15 7.5 2.~ o 79 MA 11 7.3 .1 !! 134 212 J) I 26 9 o 2.5 19 NA 11 7.3 100 111 19;) 314 SQ9 27 o 82 NA 5.2 141 176 13. 4lJ m 28 82 NA 131 7.3 27 30 50 99 2H 2'1 2 81 NA 131 7.3 o 3. 57 15 30 3 81 NA 132 1.3 o o 28 '0 52 52 31 b o 80 NA Il0 44 91 75 liB 21, 590 32 o 14 80 NA 13l o HA () 3S NA 33 2B 1.: 80 NA 1~1 5.5 o ~ fIA Q 70 HA 34 5. ~ 0.0 o 4.4 80 NA 128 6.2 27 34 30 WI 151 178 35 4.a 1.2 Q 4~4 5.53 BO NA m b.2 20 31 24 74 94 131 o 5 2.75 ~A eo NA 135 B.3 13 18 o 25 laB 9 ~ 9 60 HA 111 !1 6.S 24 Z9 !II. 3. 53 38 9 5.8 ~~B 70 NA 121 11 2.6 34 56 NA 124 151 39 9 o 3.4 3.4 80 HA 131 3.5 3.1 63 75 NA 201 33.01 10 12 o •• 2 0.2 60 NA II b.5 25 NA 4! 12 o 4 , 70 HA 11 1.2 NA 1•• 12 !2 o 2.3 80 NA 132 11 4.7 99 NA 514 I~ 6 0.2 12.47 ,0 NA 120 11 NA 22 MA 21 37 44 4 S 70 NA 126 11 b 91 NIl 107 2B2 45 2.3 4.b7 80 NA 136 U 7.l B5 101 NA 202 523 MIX MATRIX AND TEST RESULTS-Continued

S-.1tI11~ 1"!Hhtl'if' ttt:tuilT1gs Itt, pet ./S WIC Shlrry ! Dr", 28-day SltHI:P, 28-oay Ply tenHle 5tfE"ngt1'l, ;l51 NV :..mconnr:ed :otpressnl! strenqH, pSI :10. fh n In settleltfnt, C... et I • Plt-'UT,·u ; I KIln ftor"d densl tr '/ deOSl t"t. wet 28 day i 12~ a" 1180 ;.y 7 oay 23 ~iY 112Q day IBI) oay asn I ,l'g slag dust w.. l. wt pet, lbllt3 denSIty, pet Ib!ft3 I \ ! I

6 al NA !lS 4.2 20 28 lBa 6.5 6.5 81) IH l.b25 l.b 23 29 100 186 83 121 3.1 50 82 192 19! 62 123 1.5 4.2 41 72 71 127 183 4.5 80 119 4.2 33 45 45 65 !38 2.5 94 123 0 2.1 11 69 8, 17: 21) 82 125 lollS 4.2 45 69 69 174 a 3.5 79 2.06 50 56 bO 14\ tt8 221 to 10 95 1.04 128 m 16\ Jab 50~ 645 11 10 2.5 81 125 1.125 3.1 82 III 144 195 ~67 Sus 12 10 79 6.3 55 67 82 140 !\5 242 13 12 1.5 34 2.1 142 16E 168 558 796 eo'? 14 12 124 4.2 7B 117 130 ii' m 519 , < 15 12 2.5 <•• 124 2.25 3.1 9b 114 l2! 335 430 ~09 16 4.5 1.5 3.52 •• 09 il3 121 3.1 44 17 82 146 194 293 17 4.5 1.5 4 5.J3 62 NA m 0.5 3.1 37 46 GO 145 202 267 IB 4.5 1.5 4.5 II ao MA 125 3.. :'5 4.2 32 44 58 b9 11:' lBO 19 b 1 2.5 3.JJ 64 NA 13·) 4.2 n !l4 135 286 ~n 556 20 , 92 NA m S5 102 P' 2Db 3{)(1 410 21 4.67 79 NA 124 1.75 3.1 40 eo 159 223 303 22 1~:, 2 l.6} 85 NA l27 2~ 1 19 us 1D2 J27 435 712 23 7.5 2.5 61 NA 3.1 BIl 121 140 276 391 ~H 24 7.5 2.~ 19 NA 3.5 45 94 85 175 250 350 25 3 2.5 .. 3.33 79 NA m 2.25 :.8 89 IO~ lvl 271 376 50b 26 2.b7 82 NA m 3.1 128 157 185 m 596 B21} 27 B 82 NA 126 0.5 3.1 23 4. 50 109 131 1.77 28 12 81 NA 125 0.75 3.B o o o )) 94 109 2.33 4.b6 80 NA 125 1.15 3.1 48 83 105 173 lBli 4:'4 30 o 8.2 8.2 7. NA 120 1 3.1 16 19 I? 39 55 50 59 31 b I) 5.b 5.6 76 NA III 1.25 ! 28 1S 63 100 90 101 32 8 o u o 4.3 4.3 76 HA 1!8 1.25 35 ~9 51 91 129 136 153 33 10 o o I) 3.5 3.5 16 NA 121 7.5 50 5\ 60 14S 195 240 258 34 12 o o ~ 2.9 2.9 7. NIl 120 7.5 56 71 82 171 243 21]1] 347 35 4.5 1.5 o 5.b 1.44 16 NA 118 7.5 15 11 ~A 46 a1 113 106 36 a 2 o 4.3 5.a9 76 IIA 119 3.25 25 51 47 83 120 m 180 37 7.5 2.5 o o 3.5 U3 76 NA 120 9.5 52 51 74 114 In 250 27! 38 3 o o o 2.15 3.'n 76 NA 121 10 NA ~~ NA 132 207 317 33B 39 3 o o o 5.5B 11.15 76 NA 122 11 13 6 10 4b 54 B3 IDS 40 2 o 8.21 16.42 16 HA 121 11 o o 32 39 47 63 41 3 o B.21 3M5 76 NA 123 11 o o 27 37 52 56 42 6 2.92 5.9 76 HA 123 11 2S 89 62 81 129 241 306 43 0.6 4.4 U9 80 HA 20 37 45 78 U5 135 151 44 1.2 4.42 5.52 80 NA 124 2.25 21 34 43 a7 82 l!J 124 45 5 I) 2.77 NA 80 HA 125 3.75 lB U 78 11>5 199 4b o 14 2.04 NA 80 HA 122 2.75 NA o 39 43 NA < < 47 28 1.14 NA au NA 122 2.5 •• J II NA o 103 130 NA

NA Hot ,Yall.ble. NIB Ra.tio of lfat~r-to~cH~nt, fly aS~l, hIt! dust, and oil snale retorted .. aste. './e War.er-to-celent ratlo. 17

APPENDIX B.-STATISTICAL DEFINITIONS FOR GOODNESS-OF-FIT

Linear Correlation Coefficient.-Given a set of data (X;, where Yj == dependent variable, yJ, the linear correlation coefficient, r, is defmed by Yi == fitted (derived) dependent variable, n . I (xt - X)(Yj - y) and y == sample mean of Yj. I = 1 r == If there is only one predictor variable, R reduces to r. An R-value of 1 indicates that the model provides all neces­ sary information; R == 0 implies that the p-dimensional hyperplane is an inadequate model. where x and yare the respective means of the input data. Index of Determination.-The index of determination, I, MUltiple Correlation Coefficient.-As stated in reference is defmed by 15, when using a multiple-regression model, there exists one dependent and 'p' predictor variables. The multiple n correlation coefficient, R, measures the percent of I (Yi - yi variation accounted for by the model. It is defined by i == 1 r == I - --=-n---- n I (Yi - yi I 1 = 1 R2 '" 1--:::"n---- If the model being tested is linear, I is equivalent to either I r or R. The index is useful in that it can be used to com­ I pare goodness-of-fit of nonlinear models. 18

APPENDIX C.-LINEAR REGRESSION RESULTS FOR TAILINGS A

The following abbreviations are used in this appendix:

IDCOMP ...... 7-day compressive strength CEMENT ...... Cement content, percent of tailings Coef ...... Coefficient of variation DF ...... Degrees of freedom MS ...... Mean squares NAp ...... Not applicable Obs ...... Observation R-sq ...... R2 (multivariate correlation coefficient) R-sq(adj) ...... Rz adjusted for degrees of freedom s ...... Estimated standard deviation about the regression line SEQ SS ...... Sequential sum of squares SS ...... Sum of squares Stdev ...... Standard deviation Stdev fit ...... Standard deviation of fitted value St resid ...... Standardized residual t-ratio ...... Coefficient/standard deviation W/C ...... Water-to-cement ratio

The regression equation is 7DCOMP = -73.6 + 32.4 CEMENT - 1.40 W /e. Of the 95 observations, only 90 were used; the remaining five observations contained missing values.

Predictor

Constant ...... -73.64 59.73 -1.23 CEMENT ...... 32.356 2.672 12.11 W/C ...... -1.396 8.729 -.16

s = 69.42 R-sq = 87.9 pct R-sq(adj) = 87.6 pct

Analysis of Variance

DF SS MS

Regression ...... 2 3,032,842 1,516,421 Error ...... 87 419,299 4,820 Total ...... 89 3,452,140 NAp

DF SEQSS

CEMENT ... . 1 3,032,719 W/C ...... 1 123 19

Obs. CEMENT 7DCOMP Fit 8tdev fit Residual 8t resid 1 4.0 48.00 44.20 26.66 3.80 O.06X 2 6.0 70.00 112.68 10.83 -42.68 -.62 3 8.0 112.00 179.35 8.41 -67.35 -.98 4 10.0 212.00 245.28 9.04 -33.28 -.48 5 12.0 278.00 310.76 9.27 -32.76 -.48 6 .. ,. '" 14.0 340.00 376.03 9.53 -36.03 -.52 7 4.0 79.00 48.11 11.33 30.89 .45 8 4.0 48.00 47.41 12.03 .59 .01 9 4.0 54.00 46.71 14.12 7.29 .11 10 6.0 196.00 115.61 16.17 80.39 1.19

11 6.0 141.00 114.91 12.89 26.09 .38 12 6.0 118.00 114.22 10.44 3.78 .06 13 4.0 25.00 45.41 20.05 -20.41 -.31 14 7.0 106.00 145.95 8.91 -39.95 -.58 15 9.0 171.00 212.39 8.73 -41.39 -.60 16 11.0 274.00 278.13 9.52 -4.13 -.06 17 13.0 431.00 343.53 9.77 87.47 1.27 18 16.0 481.00 441.10 10.30 39.90 .58 19 5.0 114.00 78.93 15.58 35.07 .52 20 8.0 158.00 179.07 8.10 -21.07 -.31

21 10.0 259.00 245.32 9.20 13.68 .20 22 13.0 459.00 343.31 9.03 115.69 1.68 23 15.0 518.00 408.63 9.91 109.37 1.59 24 18.0 603.00 506.14 12.12 96.86 1.42 25 0.0 14.00 " " " .. 26 4.0 47.00 44.86 23.02 2.14 .03X 27 6.0 95.00 113.21 9.67 -18.21 -.26 28 8.0 130.00 179,74 9.38 -49.74 -.72 29 11.0 183.00 277.91 8.69 -94.91 -1.38 30 13.0 160.00 343.35 9.16 -183.35 -2.66R

31 14.0 365.00 376,05 9.61 -11.05 -.16 32 0.0 0.00 * " " 33 4.0 72.00 45.41 20.05" 26.59 .40 34 7.0 83.00 145.95 8.91 -62.95 -.91 35 9.0 135.00 212.39 8.73 -77.39 -1.12 36 11.0 308.00 278.13 9.52 29.87 .43 37 13.0 324.00 343.53 9.77 -19.53 -.28 38 16.0 428.00 441.10 10.30 -13.10 ·.19 39 5.0 79.00 79.42 13.45 -.42 ·.01 40 8.0 131.00 179.39 8.48 -48.39 -.70

41 11.0 295.00 277.91 8.69 17.09 .25 42 13.0 361.00 343.50 9.67 17.50 .25 43 16.0 529.00 441.16 10.37 87.84 1.28 44 19.0 772.00 538.63 13.35 233.37 3.43R 45 8.0 129.00 179.39 8.48 -50.39 -.73 46 12.0 270.00 310.76 9.27 -40.76 -.59 47 16.0 457.00 441.16 10.37 15.84 .23 48 20.0 497.00 571.16 14.70 -74.16 -1.09 49 24.0 744.00 700.97 21.62 43.03 .65 50 28.0 803.00 830.68 29.88 -27.68 ·.44X 51 0.0 0.00 " " 52 5.0 88.00 78.93 15.58" 9.07 .13" 53 8.0 154.00 179.07 8.10 -25.07 -.36 54 10.0 264.00 245.32 9.20 18.68 .27 55 13.0 341.00 343.31 9.03 -2.31 -.03 56 15.0 501.00 408.63 9.91 92.37 1.34 57 18.0 357.00 506.14 12.12 -149.14 -2.18R 58 5.0 152.00 78.93 15.58 73.07 1.08 59 8.0 80.00 179.07 8.10 -99.07 -1.44 60 10.0 233.00 245.32 9.20 -12.32 -.18 20

Obs. CEMENT 7DCOMP Fit Stdev fit Residual St resid 61 13.0 363.00 343.31 9.03 19.69 0.29 62 15.0 492.00 408.63 9.91 83.37 1.21 63 18.0 623.00 506.14 12.12 116.86 1.71 64 0.0 0.00 " .. * 65 4.0 71.00 45.41 20.05" 25.59 .38 66 7.0 134.00 145.95 8.91 -11.95 -.17 67 9.0 179.00 212.39 8.73 -33.39 -.48 68 11.0 307.00 278.13 9.52 28.87 .42 69 13.0 292.00 343.53 9.77 -51.53 -.75 70 16.0 451.00 441.10 10.30 9.90 .14

71 4.0 130.00 48.81 12.25 81.19 1.19 72 4.0 113.00 48.11 11.33 64.89 .95 73 4.0 88.00 47.41 12.03 40.59 .59 74 7.0 215.00 147.97 13.85 67.03 .99 75 7.0 137.00 147.27 10.81 -10.27 -.15 76 7.0 103.00 146.57 8.95 -43.57 -.63 77 0.0 0.00 .. .. * * 78 5.0 89.00 79.42 13.45 9.58 .14 79 8.0 140.00 179.39 8.48 -39.39 -.57 eo 11.0 441.00 277.97 8.89 163.03 2.37R

81 13.0 325.00 343.53 9.77 -18.53 -.27 82 16.0 466.00 441.19 10.41 24.81 .36 83 19.0 668.00 538.66 13.32 129.34 1.90 84 4.0 107.00 48.81 12.25 58.19 .85 85 4.0 99.00 48.11 11.33 50.89 .74 86 4.0 69.00 47.41 12.03 21.59 .32 87 8.0 149.00 180.33 11.68 -31.33 -.46 88 8.0 122.00 179.63 9.04 -57.63 -.84 89 8.0 eo.OO 178.93 8.08 -98.93 -1.43 90 8.0 125.00 179.45 8.59 -54.45 -.79

91 12.0 216.00 310.80 9.42 -94.80 -1.38 92 16.0 322.00 441.19 10.41 -119.19 -1.74 93 20.0 420.00 571.18 14.66 -151.18 -2.23R 94 24.0 610.00 700.99 21.58 -90.99 -1.38 95 28.0 824.00 830.69 29.83 -66.69 -.11X * Calculation not possible. Zero value involved. R Denotes observation with large standardized residual. X Denotes observation whose X value gives it large influence. 21

APPENDIX D.-MATHEMATICAL REPRESENTATIONS AND INDICES OF DETERMINATION FOR EXPONENTIAL CURVES RELATING COMPRESSIVE STRENGTH TO WATER-TO-CEMENT RATIO

Index of determination, I Tailings A, B, and C: IDCOMP = 1,541.04e-O.58 w/e 0.796 O64 28DCOMP = 2,782.30e- . w/e .764 120CDOMP = 3,690.00e-O·58 W Ie .658 180DCOMP = 1,035.80e-O.25 W Ie .410

Tailings A, total: IDCOMP = 1,515.53e-O.57 w/e .889 28DCOMP = 2,836.17e-O.62 w/e .843 120DCOMP = 4,OO8.05e-O·55 W Ie .711

Tailings B, total: O79 IDCOMP = 2,632.73e- . W Ie .944 28DCOMP = 3,734.56e-O.79 w/e .893 O 120DCOMP = 2,969.06e- .57 W Ie .866 180DCOMP = 1,587.58e-O.35 W Ie .632

Tailings C, total: IDCOMP 61O.85e-O.29 w/e .343 28DCOMP = 792.36e-O.27 W Ie .283 120DCOMP = 862.11e-O.22 W Ie .358 180DCOMP = 891.91e-O.21 W Ie .312

Tailings A, no additives: 7DCOMP = 1,106.35e-O.50 w/e .982 28DCOMP = 1,812.46e-O.54 W Ie .975 120DCOMP = 1,940.58e-O.50 w/e .976

Tailings B, no additives: 7DCOMP = 2,692.67e-O.79 W Ie .956 28DCOMP = 4,392.84e-O.88 w/e .920 120DCOMP = 4,316.1ge-O.77 W Ie .950 O50 180DCOMP = 1,772.37e- . W Ie .948

Tailings C, no additives: 7DCOMP = 1,352.77e-O.65 w/e ...... 892 O69 28DCOMP = 2,OO4.24e- . W Ie ...... 879 120DCOMP = 1,832.01e-O.58 w/e ...... 839 O58 180DCOMP = 1,860.52e- . W Ie ...... 904 DCOMP 7-,28-, 120-, or 180-day compressive strength. W IC Water-to-cement ratio.

~ u.s. GOVERNMENT PRINTING OFFICE 611-012/00.081 Il\'T.I3U.OF MINES,PGH.,PA 28913