POLYNOMIAL MODELS FOR PREDICTING TIME LIMITS FOR COMPACTION AFTER MIXING OPERATION OF LATERITIC SOIL REINFORCED USING CEMENT OR LIME

The demand for natural aggregates has increased in recent years because of diverse environmental interests. Consequently, its cost has soared astronomically and the utilization of lateritic soil for low-cost roads has been an attractive option. In most cases during road construction, unprecedented conditions may lead to delays in the compaction of the treated soil after the mixing operation and placing had taken place. Thus, this study developed polynomial models for predicting time limits for compaction after mixing operation within 0-180 minutes at 30 minutes intervals for lateritic soil reinforced with cement and lime. The percentage contents by weight of the dry soil for cement or quick lime mixed with the soil were 2, 4, 6, 8 and 10%. Consistency indices tests and particle size analysis were carried out on the untreated lateritic soil for characterization. The tests conducted on the lateritic soil prepared with cement and quick lime were compaction test (Standard Proctor), California Bearing Ratio (CBR) and unconfined compressive strength (UCS) of 7 days curing. The AASHTO soil classification system and Unified Soil Classification system rated the lateritic soil to be A-6(13) and clayey soil (CL), respectively. Ordinarily, the lateritic soil was found to be a poor construction soil and therefore requires treatment to improve its strength in order to make it useful for pavement purposes. At the increase in time limits for compaction after mixing, there were reductions in compaction and strength characteristics of the lateritic soils that were prepared with cement or lime. The polynomial models developed were a good fit for predicting time limits for compaction after mixing using cement/lime contents, compaction and strength characteristics of the strengthened soil. The polynomial models gave coefficients of correlation and determination of 0.988 and 0.976, respectively, when the soil was prepared with cement whereas, in the case of lime-prepared soil, the values were 0.966 and 0.933, respectively. The cement/lime contents, optimum moisture content (OMC), CBR and UCS (7 days curing) were entirely statistically significant in predicting time limits for compaction after mixing at a 95% confidence level.