Preparation and composite strengthening of desert sand artificial aggregates and their influence on concrete mechanical properties

Desert sand offers a vast yet underutilized resource for producing artificial aggregates to alleviate aggregate shortages in desert-region infrastructure. In this study, high-quality desert sand artificial aggregates (DSAAs) were produced via cold-bonding granulation. Key processing parameters, including cement content (25-45%), water-to-solid ratio (0.10-0.12) and rotation speed (40-50 rpm), were systematically optimized. A composite strengthening strategy combining internal and surface strengthening was proposed. Internal strengthening was achieved by incorporating silica fume, slag, and CaO during granulation, while surface strengthening was realized via soaking in sodium silicate solution or coating with a cement-silica fume slurry. Under optimal conditions (35% cement content, 0.11 water-to-solid ratio, 40 rpm), DSAAs exhibited a single particle compressive strength (SPCS) of 6.73 MPa, with 24 h water absorption of 4.14%. Internal strengthening combined with sodium silicate solution soaking increased SPCS to 7.03 MPa, with 24 h water absorption reduced to 3.31%, whereas cement-silica fume slurry coating further enhanced SPCS to 7.42 MPa and decreased water absorption to 3.20%. The best-performing DSAAs were used to replace 0-100% of natural coarse aggregates (NCAs) in concrete, achieving improved workability with slump values ranging from 175 to 275 mm and maintaining compressive strength above 45 MPa even at full replacement. In addition, a stress-strain model of concrete considering the replacement rate of DSAAs was established ( R ² > 0.98) based on the modification of an existing stress-strain model. This study established a closed-loop framework integrating process optimization, performance enhancement, and case verification, providing reference for desert sand utilization in sustainable construction.