Abstract:
This work assessed the combine effect of wood ash and lime on the geotechnical properties of expansive soils. The wood ash used was a waste product from bakery industry while the lime was of industrial grade. The soil was sampled from the location of the study area where engineering structures have been damaged by the expansive soil that underlain the area. The chemical composition of the wood ash and the mineralogical composition of the soil were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD) method respectively while the geotechnical properties such as grain size analysis, Atterberg limits, linear shrinkage, free swell index, optimum moisture content, maximum dry density, and unconfined compressive shear strength were carried out on the natural soil and that of the soil with varying proportion of wood ash and lime. The XRD results revealed that the soil contains appreciable amount of expansive clay minerals; vermiculite, smectites, and mixed layer clays, while the XRF result revealed that the wood ash has substantial amount of calcium oxide with high pH value and can be used as soil stabilizing additives. The natural soil was classified as highly plastic inorganic soil with high swell potential, high expansivity, and high activity. The addition of wood ash reduced the activity and linear shrinkage of the soil up to acceptable standards but failed to improve significantly the other geotechnical properties of the soil such as free swell, compaction properties and shear strength, but on addition of lime to the optimum wood ash-soil admixture lead to drastic reduction in the free swell potential, improvement in the compaction properties and increase in strength value which also improved drastically after 28days of curing the treated samples. The optimum lime-wood ash-soil admixture was 4-18-78 in weight percentage. 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.
