Effect of aeolian sand and recycled composite micro-powder on mechanical properties of ultra-high performance concrete

Ultra-high performance concrete (UHPC) was prepared by partially replacing cement with recycled composite micronized powder. The waste bricks and concrete were used as an auxiliary cementitious material. The river sand was partially replaced with anthracitic sand. The modified Andreasen-Andersen (MAA) particle accumulation model was used to design the proportions. A concrete strength growth prediction model considering the pozzolanic activity of aeolian sands and composite micro-powder was built. The effect mechanism of composite micro-powder and aeolian sand on the mechanical property of UHPC was studied. The results show that the mechanical properties of UHPC are optimal when the replacement rate of river sand by the equivalent mass of aeolian sand is 30wt% and the replacement rate of cement by the equivalent mass of composite micro-powder is 10wt%. The particle size distribution of granular materials is the best, forming a matrix with high compactness. At the same time, the hydration contribution of aeolian sand and composite micro-powder active components improves the microstructure and mechanical properties of UHPC.