Uniaxial compression mechanical properties and energy evolution of manufactured sand concrete after high temperature

With the depletion of natural sand (NS) resources and increasing restrictions on sand mining, manufactured sand (MS) has emerged as a sustainable alternative as fine aggregate in concrete. However, the influence of stone powder (SP) contained in MS on the mechanical performance of concrete under elevated temperatures remains unclear. In this study, C40-grade manufactured sand concrete (MSC) with varying SP contents ( r = 0%, 5%, 10%, 15%, and 20%) was exposed to different high temperatures ( T = 200 °C, 400 °C, and 600 °C), followed by uniaxial compression tests and microstructural analyses, to systematically evaluate its the mechanical response, energy evolution, and damage behavior. The results show that SP content significantly affects the workability and residual mechanical properties after thermal exposure, with the optimal performance—in terms of peak stress, peak strain, and elastic modulus—achieved at an SP content of 10%. Regression models incorporating both T and r were established to predict key mechanical parameters, showing good predictive accuracy. A high-temperature damage constitutive model was developed based on Lemaitre’s strain equivalence principle and Weibull statistical distribution, which accurately predicted the stress-strain evolution of MSC under various thermal conditions and revealed an ‘S’ shaped growth trend in the total damage variable D with increasing strain. In the pre-peak phase, MSC predominantly accumulates elastic strain energy, whereas in the post-peak phase, elastic energy is rapidly released and dissipated energy increases significantly. This study provides theoretical and technical support for the structural design and performance evaluation of MSC in high-temperature environments.