| Summary: | Smouldering and thermal remediation processes can achieve rapid removal of organic contaminants from soils but these processes expose soils to high temperatures for extended periods of time. Wild fire research shows changes in soil properties, when exposed to temperatures up to 850°C. Based on temperatures achieved during smouldering, this work aims to investigate how high temperature thermal and smouldering treatments affect soils. Laboratory experiments on simple soils prepared from silica sand and silica sandkaolin show that thermal treatments affect soil particle size distribution, mass, pH, mineralogy, liquid limits, and plastic limits. Properties such as particle density and bulk density remain unchanged after exposure to elevated temperatures. In silica sand, shear strength decreases with increasing temperature and smouldering whereas it increases with increasing temperature in the sand-kaolin soil. High temperatures and smouldering may smooth the sand particle surfaces and reduce interparticle friction. The presence of kaolin may protect the sand grains from this effect and affect the shear strength through mineralogical changes. Kaolin addition has similar effects on hydraulic conductivity. Samples containing 10% kaolin show a relationship between hydraulic history, microstructure and hydraulic conductivity. Samples treated by smouldering have lower saturated hydraulic conductivities compared to furnace treatments. For silica sand no changes in hydraulic conductivity were observed. These changes in dynamic response were linked to changes on a particle scale such as chemistry, mineralogy, and composition.
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