Thermal treatment of soils has been used
in the past and proven to increase soil properties. Heating clayey soil at temperatures
exceeding 400°C leads to pronounced (irreversible) permanent changes of its
engineering properties. Clayey soils with prolonged exposure to increased
temperatures have reduced sensitivity to water, show notable increases in shear
strength, and decreased compressibility. These results can be varied by heat
application type, time of exposure, and temperature. In addition, the
mineralogical composition of the clay dictates the final properties. As seen in
Figure 3, from studies conducted by Kezdi, the clay's lattice gradual loss of
water happens at different temperatures; in particular, all free water has
evaporated at 105 - 110°C. About 500° C
typically is the temperature where all water has been burned off (Hausmann,
1990)..
Laboratory
investigations by Beles and Stanculescu (Figure 4) show decreases in plasticity
after longer durations of thermal exposure. Further, the compressibility of
clay soils can be reduced due to exposure of high temperature,
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