The Effect of Heat on the Properties of Expansive Clay Soil

The cost of cut to spoil of expansive soils during construction of infrastructure projects such as roads, airports, and housing estates has continued to increase due to high cost of excavation and haulage and the increasing scarcity of spoil areas due to development. Further, suitable borrow materials continue to deplete, with their locations getting further and further from the location where they would be required. The environmental consequences of cut to spoil and borrow to fill continue to soar. This has led into continuous research into suitable ways of improving and using expansive clays. Most research methods currently concentrate on attempting to stabilize these soils. The need to eliminate cut to spoil of expansive clays followed by borrowing suitable material for fill led to this research - improving the performance of expansive clays by subjecting it to high temperatures in a closed kiln to eliminate emission of greenhouse gases. This paper reports the effect of heating the expansive clay for 2 hours at a temperature of 6000C. The properties of the neat material were investigated which included compaction, the California Bearing Ratio (CBR), grading, atterberg limits, linear shrinkage, free swell, chemical composition and loss on ignition (LOI). The same properties were investigated for the heated expansive clay. The heating increased the maximum dry density (MDD), the CBR, altered the particle size distribution, reduced the plasticity index, the free swell and linear shrinkage hence reduction in plasticity. The properties of the expansive soil were therefore improved. It was concluded that subjecting the soil to 6000C makes it suitable as a fill material.