The Effect of Heat on the Properties of Expansive Clay Soil

Abstract

Abstract: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 600 0 C. 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 600 0 C makes it suitable as a fill material.

A Review Study of Techniques and Use of Thermal Stabilization of Soil

“…Charles K. Kabubo et al (2017) carried out the study on 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.…”

A double-porosity formulation for the THM behaviour of bentonite-based materials

“…However, a great amount of energy is associated with the removal of water from the interlayer space. In order to remove most of the adsorbed water without producing any important structural changes in expansive clays, it is necessary to submit the soil sample to an oven drying procedure, in which temperature usually ranges between 100°C and 110°C (Basma et al, 1994;Caputo, 1996;Kabubo et al, 2017b). An isothermal laboratory procedure to reach such high suctions at which microstructure becomes unsaturated consists in imposing the vapour equilibrium between the pore-water potential of the dry soil and a reference atmosphere (imposed by a salt solution) with a known potential (Hoffmann, 2005;Rizzi et al, 2012).…”

“…The more appreciable effect of applying elevated temperatures to a mass of soil is the possibility of changing its properties and particle size distribution with the formation of granules and bricklike material (Kabubo et al, 2017a(Kabubo et al, , 2017b due to the thermally-induce aggregation and fusion of the fine-grained particles. In clayey soils, such thermal loadings tend to reduce the compressibility, the plasticity index and the water-clay attractiveness while the soil permeability is increased due to its desiccation and cracking.…”

“…In clayey soils, such thermal loadings tend to reduce the compressibility, the plasticity index and the water-clay attractiveness while the soil permeability is increased due to its desiccation and cracking. In expansive clays, heating also tends to cause a decrease in their swelling potential, cohesiveness and water retention capacity and an increase in their strength (Arifin, 2008;Wang et al, 2008;Kabubo et al, 2017aKabubo et al, , 2017b. If temperatures are sufficiently high and the heat exposure time is long enough, these thermal changes are irreversible, resulting in a harder, non-plastic and non-expansive soil due to partial or total destruction of the original clay crystalline structure and the formation of particles in the range of gravel fraction.…”