Damage Characteristics and Life Prediction of Desert Sand Concrete Under the Combined Effect of Continuous Axial...

To evaluate the durability of desert sand concrete (DSC) in a semi-buried saline-alkali soil environment, this study examined DSC with a 30% desert sand replacement rate, using ordinary concrete (OC) as a control. A 180-day mixed salt attack test was conducted under continuous axial compressive loads (0, 30% f_c, and 50% f_c) and semi-immersion in a mixed salt solution (5% NaCl + 5% Na₂SO₄). Macroscopic and microscopic tests were conducted to reveal the damage evolution patterns of DSC, and a life prediction model was established using a nonlinear Wiener process. The results indicate that after 180 days of semi-immersion, under identical exposure media and load levels, DSC exhibited overall better durability retention compared with OC. A 30% f_c load helped reduce pore connectivity in the DSC, suppressing the development of harmful and highly harmful pores and delaying performance degradation, whereas a 50% f_c load promoted microcrack propagation and pore connectivity, accelerating degradation. Under mixed salt semi-immersion conditions, the "wick effect" caused distinct regional damage in DSC; compared with the corresponding soaking section, the adsorption section showed 3.84-5.17% lower K_n values for compressive strength and a 25.57-42.52% higher proportion of harmful and highly harmful pores. The developed nonlinear Wiener model can reasonably characterize the relative degradation process of DSC under different exposure conditions, and the predicted trends are in good agreement with the results of macro- and micro-scale analyses.