Experimental study on the variation of physical and mechanical properties of rock after high temperature treatment

Abstract

The changes of mineral components, internal structure and water content of the rock after heating lead to the variation of the physical and mechanical properties. This paper aims to study the thermal effect (from 25 °C to 500 °C) on physical and mechanical properties (such as mass, density, porosity, P-wave velocity, compressive strength, peak strain, elastic modulus) of rock. A lot of reported results about it were summarized and many complementary tests have been carried out, the results indicated that: (1) Based on the temperature interval of the escaping of adhered water, bound water and structural water, the temperature range in 25 °C–500 °C can be divided into three stages: from room temperature to 100 °C, 100 °C–300 °C and 300 °C–500 °C. In the second and third stages, the porosity, permeability and acoustic emission of rock increase significantly, while the wave velocity is keeping falls. The temperature ranges in three previous stages are corresponding. (2) The physical and mechanical properties of rocks such as compressive strength, tensile strength, permeability and wave velocity change apparently in temperature from 200 °C to 500 °C. In the range of 200 °C–300 °C, the strong bound water's loss leads to the increasing number of micro fracture and a better connectivity. In the temperature range of 400 °C–500 °C, the change of rock's property is related to the dehydroxylation of the losing constitution water and solid mineral's expansion, which can be described as the volume becomes bigger and the number of micro-cracks increases rapidly, at the same time, the tensile strength, compressive strength and wave velocity decrease.