Effect of temperature on thermal properties and residual strength of coal gangue concrete

Abstract

Key factors for assessing the high-temperature resistance of coal gangue concrete are high-temperature residual strength and thermal properties. The high-temperature residual strength, high-temperature thermal conductivity, high-temperature specific heat capacity, and high-temperature density of concrete with various coal gangue coarse aggregate replacement ratios were tested using experimental methods in this paper to study the high-temperature resistance of coal gangue concrete. Thermal density and high-temperature residual strength tests took into account influencing factors like the water-cement ratio (0.50, 0.45, 0.40), aggregate replacement ratio (0, 25 %, 50 %, 75 %, 100 %), and temperature variation (room temperature, 200 °C，300 °C，400 °C，500 °C，600 °C，700 °C，800 °C), while thermal properties tests considered the effects of various coarse aggregate replacement ratios and temperatures. The study showed that when the temperature rises, coal gangue concrete's thermal density falls, mass loss rises, residual strength declines, thermal conductivity rises, and its specific heat capacity fluctuates. At temperatures between 20 °C and 400 °C, concrete's residual strength decreases with an increase in the coal gangue coarse aggregate replacement ratio, while thermal conductivity and specific heat capacity increase. At temperatures between 500 °C and 800 °C, however, concrete's residual strength slightly improves with an increased coal gangue coarse aggregate replacement ratio, while mass loss changes more. The research finally provides the formulae for calculating the high-temperature residual strength and thermal properties of coal gangue concrete based on the test results.