Utilisation of fly ash to improve the engineering properties of lateritic soil

Abstract

This study examined the potential utilisation of fly ash obtained from a coal fired thermal power station to improve the engineering properties of a residually derived lateritic soil. The evaluation involved the determination of a number of geotechnical parameters used to assess performance of stabilised earthen materials such as index properties, compaction characteristics, hydraulic conductivity, compressive strength and desiccation induced shrinkage. Soil mixtures with varying proportions of fly ash (0%–20%) were compacted at predetermined optimum moisture contents with three compactive efforts namely British Standard Light (BSL), West African Standard (WAS) and British Standard Heavy (BSH) that represent the minimum, medium and maximum efforts expected in the field. Results showed that the plasticity index (PI), dry unit weight, hydraulic conductivity and desiccation induced shrinkage were lowered on addition of fly ash. Conversely, optimum moisture content (OMC) as well as unconfined compressive strength increased. Overall, the engineering properties of the soil were enhanced thereby producing an improved construction material whose parameters are compatible with the desired values for engineering performance.