BITUMINOUS STABILIZATION OF LATERITE MODIFIED WITH LIME FOR USE AS PAVEMENT MATERIALS

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Author

Presented To

Department of Engineering

ABSTRACT
Marginal laterites A-7-6(14), improved with hydrated lime was stabilized using bituminous emulsion with a view to improving the strength properties of the soil. The preliminary investigation conducted on the natural lateritic soil showed that the soil belongs to the CH group using the Unified Soil Classification System or A-7-6(14) soil group using the AASHTO soil classification system. The MDD decreased with higher additive blend as it decreased from 1.67 to 1.49 mg/m3 at 6 % lime with 6 % bitumen emulsion treatment. The OMC, on the other hand, decreased with higher bitumen content but increases with higher lime content. The decreases may be due to the effect of breakdown of the flocculated aggregates and elimination of large pores. The UCS values showed a sharp increase from 235 to 985, 999 and 1078 kN/m2 at 6 % bitumen emulsion with 6 % lime, 6 % bitumen emulsion with 8 % lime and 6 % bitumen emulsion with 10 % lime respectively. The UCS values obtained fell short of 1710 kN/m2 specified by TRRL as a criterion for adequate stabilization using OPC. The values of 985, 999 and 1078 kN/m2 at 6 % bitumen emulsion with 6 % lime, 6 % bitumen emulsion with 8 % lime and 6 % bitumen emulsion with 10 % lime respectively on the other hand meet the requirement of 687–1373 kN/m2. The CBR value increased with higher additive content to a peak value of 47 % at 8 % bitumen emulsion with 10 % lime. The low value of CBR recorded is as a result of the ingress of water into the specimen which weakened it and reduces its strength. The CBR value obtained does not meet the 80 % value for base material but meets the 30 % requirement for sub base materials. The resistance to loss in strength increase from 14.5 for the natural soil to a peak value of 61.25 % at 6 % bitumen emulsion with 2 % lime content. The peak resistance to loss in strength value of 61.25 % fell short of the acceptable 80 %. Statistical analysis was carried out on results obtained from the tests conducted to determine significance difference on the various soil-lime-bitumen mixtures using a two way Analysis of Variance (ANOVA) with the Microsoft Excel Analysis Tool Pak Software Package. The results also showed that the stabilized soil did not meet the requirements of the Nigerian General Specifications of not more than 35% passing sieve No. 200,maximum plasticity index (PI) of 30% and liquid limit (LL) of a maximum of 50% when used as a subgrade material in road construction. However, from the test results, laterite treated with 6% bitumen emulsion plus 6% lime is recommended for use as sub-base treatment for light traffic roads