Improvement of thermally durable soil material with perlite additive

Thermal changes affect the engineering behavior of surrounding soils at energy geostructures. For that reason, there is a need for durable soils which are not affected from high temperatures or thermal cycles. Such soil mixtures can be developed by adding temperature-resistant materials such as perlite to the sand-bentonite mixtures. In this study, 10 and 20% perlite additives were added to 10 and 20% sand-bentonite mixtures, in order to develop durable soil mixture under high temperatures. Direct shear and hydraulic conductivity tests were performed under room temperature and high temperatures. The results of the experiments showed that the perlite additive reduced the dry unit weight of the sand-bentonite mixtures and had a positive effect on the shear strength of 20B-80S mixtures both under room and high temperatures. The perlite addition increased the angle of internal friction of sand-bentonite mixtures under room and high temperatures especially for 20% bentonite-80% sand (20B-80S) mixtures. The hydraulic conductivity (k) values of both mixtures increased with increasing temperature. As a results of thermal cycles, it was seen that the samples cannot turn back to their initial k values.