Plasticity of Nigerian lateritic soil admixed with selected admixtures

The plasticity characteristics (liquid limit, plastic limit and plasticity index) and cation-exchange capacity (C _EC) of lateritic soil treated with up to 10% of iron ore tailing (IOT) and waste wood ash (WWA) were evaluated using laboratory tests and regression analysis. The results showed an initial increase in the cation-exchange capacity up to 8% IOT content and 2% WWA content. The liquid limit and plastic limit initially increased with higher IOT content and then decreased, while for WWA-treated soil, the liquid limit and plastic limit decreased up to 2% WWA content and then increased up to 10% WWA content. The plasticity index decreased up to 8% for IOT and 6% for WWA and thereafter increased with increase in IOT and WWA contents, respectively. Regression analysis showed a close relationship between the experimental values and the predicted values for both IOT- and WWA-treated lateritic soil. From the results, WWA is more potent than IOT as an additive for improving the plasticity of treated lateritic soils. An optimal blend of 8% IOT and 6% WWA contents with lateritic soil improved the consistency indices for use as a subgrade material in lightly trafficked roads.