Synergistic Effect of Silica Fume and Hydrated Lime on Mechanical Properties of Re-cycled Aggregate Concrete

To enhance the recycling efficiency of waste concrete, this study systematically investigated the effects of silica fume and hydrated lime modifications (both individual and composite) on the mechanical properties of recycled aggregate concrete (RAC). The triple mixing technique (TM) was employed during concrete preparation. Compressive tests and splitting tensile tests were conducted to evaluate the fundamental mechanical properties of RAC, while scanning electron microscopy (SEM) was used to analyze its microstructural characteristics.The results demonstrated that:Individual incorporation of either silica fume or hydrated lime provided limited improvement to the compressive strength and splitting tensile strength of RAC;The composite modification using both silica fume and hydrated lime showed significant enhancement in mechanical performance;Microscopic analysis revealed that the composite system exhibited substantially improved microstructural compactness and enhanced bonding strength between aggregates and cement paste.These findings provide valuable references for the practical application of recycled coarse aggregates, suggesting that proper composite modification could effectively improve the mechanical performance of recycled concrete while promoting resource utilization efficiency.