Uniaxial compressive stress-strain model of Molybdenum tailings concrete after high-temperature exposure

Abstract

To investigate the effect of high-temperature exposure on the mechanical properties of molybdenum tailings concrete, 75 cubes and 150 prisms of molybdenum tailings concrete were tested, by considering five heating temperatures (20, 200, 400, 600, and 800 ℃) and five replacement ratios (0, 25, 50, 75, 100%). The failure modes, mass loss rate, and mechanical properties of the specimens were analyzed in detail. The experimental results indicate that with an increasing heating temperature, the color of the blocks became lighter, accompanied by gradually intensifying phenomena such as skin peeling and crack propagation. At 800 ℃, many small cracks at the fracture site of the blocks after splitting failure, and obvious fracture zones in the block under axial compression failure were observed. With an increasing temperature, the mass loss rate and peak strain of the molybdenum tailings concrete show a linear growth trend, reaching the maximum amplitude at 800 ℃ (7.85% and 192.5%), whilst the molybdenum tailings concrete splitting tensile strength, peak stress, and elastic modulus showed a decreasing trend, reaching the maximum amplitude (404%, 61.7%, and 84.9%). By increasing replacement ratios, the mass loss rate of the molybdenum tailings concrete shows a linear growth trend, with a maximum increase of 1.07%. The mechanical properties of the concrete at all temperatures show a trend of first increasing and then decreasing. A 25% replacement ratio can improve the deterioration of the molybdenum tailings concrete after high-temperature exposure, with the maximum amplitude increase of the peak stress, peak strain, and elastic modulus being 24.3%, 12.4%, and 21%, respectively. Based on the test data, the prediction formulas of the mechanical properties of molybdenum tailings under different high-temperature and molybdenum tailings replacement ratios are fitted. The existing constitutive equations are modified to establish the stress-strain constitutive model of molybdenum tailings concrete after high-temperature exposure, of which results are in good agreement with the test data.