Influence of fly ash and cement on CBR behavior of lateritic soil and sand

Abstract

The California bearing ratio (CBR) behavior of a fine grained residual lateritic soil and granular riverbank sand modified with a low calcium Class F fly ash and ordinary Portland cement was investigated with reference to their use as subgrade and subbase materials in pavement construction. The effects of different percentages of fly ash addition and cement stabilization were studied. Specimens were statically compacted at corresponding optimum moisture content and then tested for CBR. For each mix, unsoaked test was carried out on the as compacted specimen without curing, whereas soaked test was conducted after soaking the specimen for 4 days. For soil–fly ash mixes of either soil type, the soaked CBR is found to be generally lower than the unsoaked value. Upon addition of cement to the mixes, a reverse trend is observed with the soaked CBR being higher than the corresponding unsoaked value. Both soil–fly ash mixes with 50% fly ash content are suitable for use in the subgrade layer of low volume road pavements. When 1% cement is added, both the soils with 50% fly ash content can be used in the subbase layer.