Study on the influence of desert sand replacement rates on the deformation and failure mechanism of concrete

This study investigates how varying desert sand replacement rates affect deformation and failure processes of concrete. Uniaxial compression tests were conducted on concrete with varying desert sand replacement rates (substituting river sand on equal-mass basis) through such multi-index test methods as digital image correlation technology (DIC), acoustic emission (AE) and scanning electron microscopy (SEM). We discussed the effect of desert sand on the mechanical behavior and failure mode of concrete at multiple scales. Results show: ① Increasing desert sand replacement rate led to an initial increase and subsequent decrease in peak stress while peak strain showed an opposite trend. Optimal performance was observed at a replacement rate of 20%. ② AE ringing count experienced 3 stages relative to stress changes: contact, slow increase and steep increase. At low replacement rates, crack initiation was dominated by small-scale fracture; conversely, crack expanded rapidly to form large-scale penetrating cracks at high replacement rates. ③ DIC monitoring revealed a transition from tensile to shear failure as the replacement rate increased. With replacement rate ≥60%, shear cracks exceeded 50%. ④ Moderate amounts of desert sand could maintain the structural compactness of concrete and interface bonding. Low replacement rate could exert micro-aggregate filling and matrix compaction effects, yet exceeding the threshold compromised its structural integrity. This study provides theoretical basis for promoting engineering applications of desert sand concrete in desert areas.