Experimental Study on Mechanical and Microstructural Properties of Foam Concrete Incorporating Desert Sand as Partial Fine Aggregate.

The escalating depletion of river sand resources poses a critical sustainability challenge for the production of foam concrete, while the reinforcement mechanism of locally abundant aeolian sand in cementitious matrices remains insufficiently quantified. To address this gap, the present study investigates the feasibility of partially substituting river sand with Taklamakan desert sand at replacement ratios of 0%, 20%, and 40%, under varying water-to-binder (W/B) ratios (0.3, 0.4, 0.5) and sand-to-binder (S/B) ratios (0, 0.3, 0.6). To correlate macroscopic performance with microstructural features, compressive strength was tested, and pore structure evolution was characterized using deep learning-based image segmentation, supplemented by XRD and SEM analyses. Results indicate that increasing the W/B ratio from 0.3 to 0.5 elevates porosity by up to 111.7%, resulting in a 47.4% reduction in compressive strength. Similarly, raising the S/B ratio from 0 to 0.6 introduces additional interfacial transition zones (ITZs) and dilutes the cementitious phase, which consequently weakens the matrix and leads to a strength reduction of up to 66.5%. However, the contribution of desert sand replacement exhibits a pronounced "S/B ratio dependence". Notably, at an S/B ratio of 0.6 and a 40% desert sand replacement rate, the compressive strength experiences a significant increase of 51.4% compared to the control group. Quantitative analysis further reveals that the compressive strength follows positive and negative power-law relationships with dry density and porosity, respectively. Ecological assessment shows that desert sand foam concrete (DSFC) with high S/B and high desert sand replacement ratio reduces embodied CO