The combined effect of wood ash and lime on the engineering properties of expansive soils

Abstract

This work assessed the combined effect of wood ash a waste product from a bread bakery and lime (calcium oxide) on the geotechnical properties of expansive soils collected from Awgu (southeastern Nigeria). The mineralogical composition of the soil and chemical composition of the wood ash were analyzed using X-ray diffraction and X-ray fluorescence method, respectively. The geotechnical properties of the soil such as grain size distribution, consistency limits, free swell potential, compaction, and unconfined compressive strength of the natural soil and that of the soil with varying proportion of wood ash and lime was also examined. The results revealed that the natural soil which is classified as highly plastic inorganic soil, on addition of wood ash and lime in the optimum proportion of 78%-18%-4% by weight of soil-wood ash-lime admixture showed reduction in the plasticity index and linear shrinkage, thus improving the workability of the natural soil. There was also reduction in the free swell potential of the natural soil, improvement in the compaction properties of the natural soil, and increase in the shear strength value of the natural soil which drastically improved more after 28 days of curing. It was therefore concluded that high plastic inorganic soils can successfully be stabilized for use in pavement construction with the combined effect of wood ash and lime, which will not only reduce the cost of carrying out engineering projects, but also reduces the environmental problems associated with indiscriminate disposal of wood ash.