compaction delay effects on properties of lime-treated soil

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Compaction Delay Effects on Properties of Lime-Treated SoilKolawole J. Osinubi, M.ASCE1; and Charles M. O. Nwaiwu, A.M.ASCE2

Abstract: A statistical study of the effects of compaction delays on properties of lime-stabilized lateritic soil was conducted usingtwo-way analysis of variance and multiple regression analysis. The reductions in mavimum dry density �MDD� and optimum moisturecontent �OMC� associated with compaction delays are statistically significant at the 5% level, regardless of the compactive effortemployed �i.e., standard Proctor or West African Standard�. The effects of compaction delays on unconfined compressive stength �UCS�are statistically significant for different compactions, lime contents, and curing. Compaction delay effects on California bearing ratio�CBR� of soil–lime mixtures are statistically significant. The t-statistics from regression analysis show that compaction delays significantlyinfluence the measured values of MDD, OMC, UCS, and CBR. It is believed that the findings of this study will be helpful in controllingthe compaction delay for lime-treated soils.

DOI: 10.1061/�ASCE�0899-1561�2006�18:2�250�

CE Database subject headings: California bearing ratio; Soil Compaction; Lime; Compressive strength; Delay time; Regressionanalysis.

Introduction

Soil stabilization has been used in the building of roads and air-craft runways, earth dams and embankments, in erosion control�Diamond 1975; Kawamura and Diamond 1975; Yadima andNwaiwu 2001�, and in the reduction of frost heaving �Gillot1987�. The strength and durability properties of natural soils canbe improved by both mechanical and chemical stabilization.Chemical stabilization of soils involves additives such as cement,lime, bitumen, calcium chloride, etc.

With cement, the hydration process begins as soon as it isbrought in contact with the soil. Any delay after mixing allowshard “clods” to form in the soil that hinder further mixing andcompaction to high density �CIRIA 1988�. A delay between mix-ing and compaction leads to a decrease in both density andstrength for a fixed compactive effort �Mitchell 1976�. West�1959� demonstrated that strength was reduced by 50% as a resultof a 2 h delay in compaction, which halved again after a 5 h delaywhen two soils �a medium clay and a sandy gravel� were stabi-lized with 10% cement.

Lime is considered to be more appropriate for the stabilizationof clayey soils having fines contents in excess of 25% as it makessuch soils to be more friable, less plastic, and hence easier towork and compact. The hydration process in lime–soil mixtures ismuch slower than with cement–soil mixtures �CIRIA 1988�. Thereactivity of the lime is a function of the temperature and time of

1Associate Professor, Dept. of Civil Engineering, Ahmadu BelloUniv., Zaria 810001, Nigeria. E-mail: [email protected]

2Lecturer I, Dept. of Civil and Water Resources Engineering, Univ. ofMaiduguri, Maiduguri, Nigeria.

Note. Associate Editor: Hilary I. Inyang. Discussion open untilSeptember 1, 2006. Separate discussions must be submitted for individualpapers. To extend the closing date by one month, a written request mustbe filed with the ASCE Managing Editor. The manuscript for this paperwas submitted for review and possible publication on February 15, 2005;approved on July 29, 2005. This paper is part of the Journal of Materialsin Civil Engineering, Vol. 18, No. 2, April 1, 2006. ©ASCE, ISSN
0899-1561/2006/2-250–258/$25.00.
250 / JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / MARCH

J. Mater. Civ. Eng. 20

firing; temperature having the greatest effect upon reactivity�Gillot 1987�. Thus, depending on the conditions of manufactureof lime, its reaction when mixed with soil may make compactiondelays of considerable importance. The temperature of the reac-tion in soil–lime mixtures affects the rate of formation of cementi-tous compounds that bind soil aggregates together.

Compaction delays have been shown to affect certain proper-ties of lateritic soil–lime mixtures �Osinubi 1998�. The objectiveof this study is to show the effects of compaction delays on theproperties of lime-stabilized lateritic soil. Results from the studyare also used to predict the compaction and strength properties ofthe stabilized soil based on variables that include time delay.

Materials and Methods

Soil

The soil used in this study is a natural reddish-brown lateritic soilobtained from a borrow pit in Zaria �Latitude 11°15�N and lon-gitude 7°45�E�, in Nigeria, using the method of disturbed sam-pling. The soil classified as A-7-6 according to the AASHTO SoilClassification System �AASHTO 1986� and CL according to theUnified Soil Classification System �ASTM 1992�.

Lime

Hydrated lime was used as the stabilizing agent, while potablewater was utilized in the laboratory tests conducted in this study.

Index Properties and Clay Mineralogy

Laboratory tests to determine natural soil and soil–lime mixturesindex properties were conducted in accordance with BritishStandards-BS �British 1990a,b�, respectively. However, the CBRtests were modified to conform with the recommendations of theNigerian General Specifications for Roads and Bridges �Nigerian1997�, which states that specimens be cured for 6 days unsoaked
and immersed in water for 1 day before testing.
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The clay mineralogy of the material was assessed qualitativelyby differential thermal analysis �DTA� of fractions passingthrough a British Standards-BS No. 200 sieve and quantitativelyassessed by x-ray diffraction �XRD�. Results of these analysesshowed that the soil contains kaolinite with a mixture of quartz.

Compaction of Soil and Soil–Lime Mixtures

The standard Proctor and West African Standard �WAS� compac-tion procedures were utilized throughout the tests. When the BS�Proctor� compaction mould is utilized, the compactive effort forthe WAS consists of the energy derived from a 4.5 kg rammerfalling through 45 cm onto five layers, each receiving 10 blows.The standard Proctor compaction energy is easily achieved in thefield, while the WAS compaction is the conventional laboratorycompaction procedure commonly used in the West Africansubregion.

Strength Tests

Samples of soil and soil–lime mixtures were prepared by mixingthe desired proportions of potable water, soil, and lime. Percent-ages of lime ranged from 0 to 8% by weight of dry soil, whilepercentages of moisture content ranged from 6 to 30%. The soil–lime mixtures were prepared by first thoroughly mixing dry pre-determined quantities of crushed soil and lime in a mixing tray toobtain a uniform color. The required amount of water determinedfrom moisture-density relationships for soil–lime mixtures waslater added to the dry soil–lime mixtures and left for elapse times

Fig. 1. Particle size distribution of the lateritic soil

of up to 3 h �i.e., 0, 1, 2, and 3 h� before compaction at the

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energies of the standard Proctor and WAS. Specimens were curedfor 7, 14, and 28 days in case of unconfined compression,whereas CBR specimens were cured for 6 days and immersed inwater for 1 day before testing in accordance with the NigerianGeneral Specifications for Roads and Bridges �Nigerian 1997�.

Methods of Analysis

The results of the laboratory tests were first presented graphicallyto reflect trends in the effects of lime content and compactiondelays on the compaction characteristics as well as strength prop-erties of the soil. The two-way analysis of variance �without rep-lication� was then employed to assess, in quantitative terms, therelative effects of lime content, curing age, and compactive effort,as well as compaction delays on properties of the stabilized soil.The two-way ANOVA was carried out at 5% level of significance.Multiple regression analysis was also carried out in order to pre-dict properties of the soil–lime mixtures from variables that in-clude elapse times.

Results and Discussion

Properties of Soil and Soil–Lime Mixtures

The particle size distribution of the natural soil is shown in Fig. 1.The index properties of the natural soil are summarized in Table

Table 1. Physical Properties of Natural Lateritic Soil

Property Quantity

Natural moisture content �%� 7.10

Liquid limit �%� 44.0

Plastic limit �%� 24.0

Plasticity index �%� 20.0

Linear shrinkage �%� 9.5

Percentage passing BS No. 200 sieve 52.0

AASHTO classification A-7-6

Group index 6

USCS classification CL

MDD �standard Proctor� �Mg/m3� 1.84

OMC �standard Proctor� �%� 19.1

MDD �West African Standard� �Mg/m3� 1.89

OMC �West African Standard� �%� 15.7

UCS �standard Proctor� �kN/m2� 310

UCS �West African Standard� �kN/m2� 440

CBR �standard Proctor� �%� 8

CBR �West African Standard� �%� 13

Table 2. Test Matrix for Analysis of Variance

Compaction procedure

Variables Standard ProctorWest African

Standard

Lime contents 0, 3, 5, 8 0, 3, 5, 8

Compaction delays �h� 0, 1, 2, 3 �0, 0.5,1.0, 1.5, 2.0, 2.5,3.0 for MDD andOMC�

0, 1, 2, 3 �0, 0.5,1.0, 1.5, 2.0, 2.5, 3.0for MDD and OMC�

Curing ages �days� 7, 14, 28 7, 14, 28

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1. The test matrix for the two-way analysis of variance is shownin Table 2. The variations of MDD and OMC with lime contentsfor no compaction delays are shown in Figs. 2�a and b�, respec-tively. The decrease in MDD with higher lime content is notuniform. This trend may be due to the formation of transitionalcompounds that had higher densities in the range of 3–5% limecontent �Fig. 2�a��. Transitional compounds are intermediate com-pounds formed in the intermediate stage of a chemical reactionprocess. High OMC values were recorded with higher lime con-tent for soil–lime mixtures compacted at the energy level of the

Fig. 2. �a� Variation of maximum dry density with lime content and�b� variation of optimum moisture content with lime content

WAS as shown in Fig. 2�b�.



Fig. 3. Variation of unconfined compressive strength with limecontent

Fig. 4. Variation of California bearing ratio with lime content

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At no compaction delay, the UCS for the specimens cured forthe various ages generally increased with higher lime content�Fig. 3� regardless of the compactive effort used. However, somespecimens, especially those cured for 28 days before testing, ex-hibited trends of decreasing UCS values when lime content wasin excess of 5%. Excess lime contents in soils are thought to actas low strength fillers, which then result in lower values of UCS

Fig. 5. �a� Variation of maximum dry density with compaction delaysand �b� variation of optimum moisture content with compactiondelays

�Gillot 1987�. On the other hand, CBR values increased with

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higher lime content at no compaction delay after mixing. Thistrend is shown in Fig. 4 for specimens compacted at the compac-tive efforts used in the study.

The MDD values decreased with higher elapse times up to 3 h,regardless of the lime content and compactive effort used �Fig.5�a��. Compaction delays resulted in reductions in OMC �Fig.5�b��, UCS �Figs. 6�a and b��, and CBR �Fig. 7� of specimenscompacted at the energies of the standard Proctor and WAS. Thehighest UCS values for each compactive effort were obtainedwith specimens containing 5% lime and cured for 28 days, whilethe lowest UCS values were recorded for specimens containing

Fig. 6. �a� Variation of unconfined compressive strength withcompaction delays �standard Proctor� and �b� variation of unconfinedcompressive strength with compaction delays �West AfricanStandard�

3% lime and cured for 7 days �Figs. 6�a and b��.


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Two-Way Analysis of Variance „ANOVA…

The analysis of variance �ANOVA� test was employed to checkthe contributions of lime and compactive effort to variations inMDD, OMC, UCS, and CBR, respectively, when there was nodelay in compaction. The analysis was also used to assess thecontributions of compaction delay and lime content to variationsin both MDD and OMC for the two compactive efforts employed.The relative contributions of compaction delay and curing age tovariations in UCS at different percentages of lime were alsoevaluated using ANOVA. The relative contributions of compac-tion delay and lime content to variations in UCS at different cur-ing ages were similarly evaluated using ANOVA. The relativecontributions of compaction delay and lime content to variationsin CBR were also evaluated. The calculated F-values show the

Table 3. Two-Way Analysis of Variance for Zero Compaction Delays

Property Source of variation

MDD Lime content

Compactive effort

OMC Lime content

Compactive effort

UCS �standard Proctor� Lime content

Curing age

UCS �West African Standard� Lime content

Curing age

CBR Lime content

Compactive effort

Fig. 7. Variation of California bearing ratio with compaction delays



ratio of the between-samples sum of squares to the error sum ofsquares, which expresses the idea that the quantity estimates ran-dom �or chance� error. It is considered to be the value of a randomvariable having the F distribution with k−1 and k�n−1� degreesof freedom. The letter n represents the number of observationswhile k is the population or sample means. The critical F-value isthe upper limit of the F ratio and this can be found in statisticalbooks. The p-value is the tail probability for a given distribution.The p-value will be less than 0.05 �for 5% level of significance�whenever the calculated F-value is greater than the criticalF-value which is indicative of the existence of statistical signifi-cance in relation to the contributions of a given variable.

Properties of Soil–Lime Mixtures at No CompactionDelay

The relative effects of lime content and compactive efforts onMDD and OMC values are summarized in Table 3. The two-wayANOVA results show that the effects of lime content and com-pactive effort on MDD values are both statistically significant at5% level as the p-values are less than 0.05. Neither lime contentnor compactive efforts had any statistically significant effect onOMC �p�0.05� as can be seen in Table 3. Based on the calcu-lated F-values, the compactive efforts contributed more to varia-tions in MDD and OMC values than lime content.

The contributions of lime content and curing age to variationsin UCS are statistically significant at �=0.05 �i.e., p�0.05� asshown in Table 3, regardless of the compactive effort used. Thehigher values of calculated F-statistic obtained at the effort ofWAS compaction suggest that the contributions of lime contentand curing age to variations in UCS values are more significantfor this soil at higher compactive effort.

Variations in CBR values due to variations in lime content anddifferences in compactive efforts are statistically significant at 5%levels since p-values are less than 0.05. The calculated F-statisticfor the contribution of lime content �i.e., F=106.99� is more thanfive times the F-value for the contribution of compactive effort tovariations in CBR of the soil–lime mixtures �Table 3�. In general,statistically significant contributions to variations in stabilized soilproperties were established when p�0.05.

Properties of Soil–Lime Mixtures with CompactionDelays

The relative effects of differences in compaction delays and limecontents on measured values of MDD and OMC were investi-

eedom

F-value�calculated� p-value

F-value�critical�

30.38 9.57E−03 9.28

37.50 −8.75E−03 10.13

1.06 0.48 9.28

3.04 0.18 10.13

13.54 4.43E−03 4.76

9.48 1.39E−02 5.14

15.70 3.02E−03 4.76

12.50 7.11E−03 5.14

106.99 1.51E−03 9.28

18.97 2.24E−02 10.13

Degrof free

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Table 4. Two-Way Analysis of Variance for Compaction Characteristics with Compaction Delays

Property Source of variationDegree

of freedomF-value

�calculated� p-valueF-value�critical�

MDD �standard Proctor� Compaction delay 6 21.34 9.52E−06 2.996

Lime content 2 8.17 5.76E−03 3.885

MDD �West African Standard� Compaction delay 6 17.93 2.39E−05 2.996

Lime content 2 27.11 3.54E−05 3.885

OMC �standard Proctor� Compaction delay 6 8.15 1.13E−03 2.996

Lime content 2 0.84 0.46 3.885

OMC �West African Standard� Compaction delay 6 12.22 1.68E−04 2.996

Lime content 2 3.01 8.74E−02 3.885

Table 5. Two-Way Analysis of Variance for Unconfined Compressive Strength with different Percentages of Lime and with Compaction Delays


of freedomF-value


UCS �standard Proctor�

3% lime Compaction delay 3 6.05 3.02E−02 4.76

Curing age 2 6.86 2.82E−02 5.14


Curing age 2 62.55 0.60E−05 5.14


Curing age 2 9.19 1.49E−02 5.14

UCS �West African Standard�


Curing age 2 287.89 1.1E−06 5.14


Curing age 2 191.28 3.7E−06 5.14


Curing age 2 38.32 3.83E−04 5.14

Table 6. Two-Way Analysis of Variance for Unconfined Compressive Strength with Different Curing Times and with Compaction Delays


of freedomF-value


UCS �standard Proctor�

7 days Compaction delay 3 55.0 9.3E−05 4.76

Lime content 2 128.45 1.2E−05 5.14


Lime content 2 64.29 8.9E−05 5.14


Lime content 2 9.45 1.4E−02 5.14

UCS �West African Standard�


Lime content 2 80.63 4.6E−05 5.14


Lime content 2 26.3 1.07E−03 5.14


Lime content 2 11.40 9.04E−03 5.14

Table 7. Two-Way Analysis of Variance for California Bearing Ratio with Compaction Delays


of freedomF-value


CBR �standard Proctor� Compaction delay 3 13.05 4.87E−03 4.76

Lime content 2 1.34 0.33 5.14

CBR �West African Standard� Compaction delay 3 13.47 4.5E−03 4.76

Lime content 2 3.01 0.12 5.14

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gated for the compaction efforts used in this study. The results ofthe two-way ANOVA are summarized in Table 4. Regardless ofthe compactive effort used, the reductions in MDD and OMCvalues due to increases in compaction delays �Figs. 5�a and b��are statistically significant at 5% level. This is because the calcu-lated F-statistic values are, in each case, greater than the corre-sponding critical values of F-statistic �Table 4�. Compaction delayeffects are more pronounced for MDD values than for OMCvalues judging from the values of F-statistic in Table 4. The con-tribution of lime content to variations in MDD are statisticallysignificant at �=0.05 for both standard Proctor and WAS com-pactions, this contribution being more pronounced at the energylevel of the WAS with a calculated F-statistic value of 27.11. Onthe other hand, the contribution of lime content to variations inOMC values was not statistically significant for any of the com-paction energy levels with p�0.05 �see Table 4�.

The contributions of compaction delay and curing age to varia-tions in UCS were evaluated at the specified lime contents and foreach of the compactive efforts used. The results of these analysesare summarized in Table 5. Regardless of the lime content andcompactive effort used, the effects of both compaction delay andcuring age on UCS values were statistically significant�p�0.05� since calculated values of F-statistic are higher than thecorresponding critical F-values. The highest calculated F-valueswere obtained at 5% lime content with respect to compactiondelay and curing age for specimens compacted at the energy ofthe standard Proctor, while the least F-values were obtained forspecimens with 3% lime content. At the energy of the WAS com-paction, F-values indicating the relative effects of compactiondelay and curing age decreased with higher lime contents. Forexample, calculated F-values for the effects of compaction delayson UCS values decreased from 38.63 to 16.67 as lime contentincreased from 3 to 8% �Table 5�.

The combined effects of compaction delay and lime content onUCS values were evaluated statistically for each curing age and ateach compaction energy level. The results of the two-way analy-sis of variance in these cases are summarized in Table 6. Thecontributions of compaction delay and lime content to variations

Table 8. Results of Regression Analysis

Property Variables Coefficie

MDD Intercept 1.803

Compaction delay −0.030

Compactive effort −0.041

Lime content −0.007

OMC Intercept 18.390


Compactive effort 0.145


UCS Intercept 277.833



Lime content 471.041

Curing age −103.393

CBR Intercept 49.119




Optimum moisture content 1.876

in UCS values are found to be statistically significant at the two



energy levels utilized. Compaction delay effects on UCS values atthe 28-day curing age were more pronounced at the energy levelof the WAS with F=47.66 than at the standard Proctor effort withF=21.29. The F-values obtained at the two energy levels utilizedshow that the effect of lime content on UCS values decreasedwith higher curing age. The F-values for the effect of lime contentat the energy of the WAS compaction decreased from 80.63 to11.4 as curing age increased from 7 to 28 days. It is evident fromthe above considerations that compaction delay, compaction en-ergy, curing age, and lime content are variables that significantlyaffect measured UCS values.

The differences in compaction delays had significant effects onthe variations in CBR values, the effect being slightly pronouncedat the WAS compaction energy. The F-value at this energy level is13.47 which is greater than the critical F-statistic of 4.76. Limecontent effects on CBR values were not statistically significant atthe energy levels considered in this study since p�0.05 �Table 7�.

The effects of compaction delays on MDD, OMC, UCS, andCBR are statistically significant. For construction purposes, it canbe inferred from these results that for a lime-stabilized lateriticsoil, compaction delay is a factor that requires careful consider-ations. This is particularly necessary because of the decrease indry density, UCS, and CBR values associated with higher com-paction delays.

Regression Analysis

Multiple regression analysis procedure was utilized to establishrelationships for predicting MDD, OMC, UCS, and CBR. The

Standard error t-statistic p-value

0.0085 211.11 0

0.0027 −11.19 4.9E−14

0.0027 −15.15 2.1E−18

0.0013 −5.5 2.2E−06

0.3313 55.51 0

0.1048 −9.95 1.7E−12

0.1048 1.39 0.17

0.0510 −2.29 2.71E−02

268.1918 1.04 0.30

23.8924 −5.47 6.4E−07

26.7125 −4.01 1.48E−04

173.117 2.72 8.18E−03

40.7446 −2.54 1.34E−02

31.6062 1.55 0.13

2.258 −3.19 4.11E−03

1.3077 −6.74 7.19E−07

0.6319 −1.64 0.11

1.6920 1.11 0.28

Table 9. Statistical Properties from Regression Analysis

PropertyCoefficient of

determination, R2 Adjusted R2Standard error

of estimateOverall

F-statistic

MDD 0.91 0.903 0.018 128.3

OMC 0.74 0.702 0.68 35.37

UCS 0.47 0.44 266.66 14.72

CBR 0.86 0.83 6.17 29.73

nts

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independent variables in the relationships are compaction delay,lime content, compaction energy, and curing age for UCS as wellas OMC for CBR. The results of the analyses are presented inTable 8 for MDD, OMC, UCS, and CBR. The compactive effortused was represented by an index that is essentially an integercategorical value. The value of −1 was assigned to the energylevel of the WAS while the value of 1 was assigned to the energyof the standard Proctor compaction. It is conventional to employsuch indices in response surface analysis �Miller and Freund1977�. Benson and Trast �1995� used integer categorical values torepresent compactive effort when a regression model was devel-oped for predicting hydraulic conductivity.

The variables considered in the prediction of MDD were allsignificant at �=0.05 with the t-statistic being greater than 1.96�Table 8�. The values of the t-statistic suggest that compactiveeffort had the most significant influence on MDD followed bycompaction delay and lime content. The resulting values of sta-tistical properties are coefficient of determination, R2=0.91 withan adjusted R2 value of 0.903, standard error=0.018, and overallF-statistic=128.3 as shown in Table 9.

Compactive effort was the only variable that was not signifi-cant �i.e., p�0.05� among all the variables used in the regressionanalysis for OMC. Compaction delay had the most significantinfluence on OMC values as the value of the t-statistic was ob-tained as −9.95 that corresponds to a partial F-value of 99.003.The partial-F is the square of the t-statistic and represents a mea-sure of the contribution of a given variable in the prediction of thedependent variable. This analysis yielded the following values ofcoefficient of determination, R2=0.74, adjusted R2=0.762,standard error of estimate=0.68, and overall F-statistic=35.37.

The four independent variables used in the prediction of UCSwere statistically significant at 95% confidence limits. The fol-lowing order of importance of the variables was established basedon the values of t-statistic obtained, namely compaction delay,compactive effort, lime content, and curing age �Table 8�. Theregression parameters were obtained as follows: R2=0.47; ad-justed R2=0.44, standard error of estimate=226.66, and overallF-statistic=14.72. The value of R2 was quite low although thefour variables in regression analysis were all statistically signifi-cant and the overall F-statistics was significant at 5% level. Thelow R2 value suggests that there are other additional factors thatcontribute to variations in UCS. The standard error of estimate ofUCS is quite high.

In the prediction of CBR values, only compaction delay andcompactive effort made significant contributions to variations inCBR values �Table 8�. Lime content and OMC did not signifi-cantly affect CBR values with p�0.05. On the basis of the valuesof t-statistic obtained the variables fall into the following order ofimportance, namely compactive effort, compaction delay, lime

Table 10. Results of Analysis of Residuals of Regression Models

Standardized residuals

Parameter MeanStandarddeviation Variance Dmax

Dcritical

��=0.05�

MDD �N=42� 1.51E−14 0.96 0.93 0.1050 0.2099

OMC �N=42� 3.3E−15 0.96 0.93 0.1136 0.2099

UCS �N=72� −5.55E−17 0.97 0.94 0.0578 0.1603

CBR �N=24� −2.18E−15 0.91 0.83 0.0899 0.2693

content, and OMC. Values of regression properties were obtained

JOURNAL OF MATE


as follows: R2=0.86; adjusted R2=0.83; standard error of estimateof CBR=6.17, and overall F-statistic=29.73�p�0.05�. Thesevalues are shown in Table 9.

The residuals associated with the regression analysis were ex-amined for normality. The residuals in the models from multipleregression equations are taken to constitute an independent mean-zero Gaussian random-error term, �, with variance. The � valuesare assumed to have a normal distribution. The normality test isusually carried out in order to accomplish a qualitative assessmentof the validity of the normality assumption Standardized residualswere subjected to the Kolmogorov-Smirnov test for goodness-of-fit in accordance with the suggestions of Kleinbaum and Kupper�1978�. The results of the residual analysis are shown in Table 10for MDD, OMC, UCS, and CBR. The values of Dmax as well asthose of the mean and standard deviation indicate that the residu-als satisfy the normality conditions of Dmax�Dcrit andN�� ,��=N�0,1�. The term Dmax is the maximum absolute differ-ence D between the values of the cumulative distribution of aramdom sample of size n and a specified theoretical distribution.Dcrit�critical value of this difference that can be obtained fromstatistical tables.

Conclusion

A study of compaction delay effects on the properties �i.e., MDD,OMC, UCS, and CBR� of lime-stabilized lateritic soil was con-ducted statistically using two-way analysis of variance �ANOVA�and multiple regression analysis. In the case of no compactiondelay, lime content and compactive effort significantly contrib-uted to variations in MDD and CBR values but not to OMC. Limecontent and curing age had significant effects on variations inUCS values at the two energy levels utilized in the study.

Reductions in MDD and OMC values associated with compac-tion delays were statistically significant, regardless of the com-pactive effort. The effects of compaction delays on UCS are alsostatistically significant at the compaction energy levels used forthe various lime contents and curing ages of specimens. The ef-fects of compaction delay on UCS decreased with increased limecontent in WAS compaction. The effects of compaction delays onCBR values are also significant at 5% level, specifically in thecase of WAS compaction.

The t-statistics from regression analysis showed that compac-tion delays have significant influences on the measured values ofMDD, OMC, UCS, and CBR values of lime-stabilized lateriticsoil. Therefore for construction purposes compaction delays needto be carefully examined as they can result in significant reduc-tions in the properties investigated. One lateritic soil has beeninvestigated in this study. The responses of lateritic soils withvarying plasticity indices should be investigated to reach suchconclusions.

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