Experimental study on the performance of manufactured sand concrete with mineral admixtures

The incorporation of blast furnace slag powder (SP) and limestone powder (LP) markedly influences the performance of manufactured sand concrete (MSC), yet their optimal dosages and underlying mechanisms remain unclear. This study investigates the effects of SP and LP on the workability, mechanical properties and durability of MSC, complemented by scanning electron microscopy (SEM) analysis. Results show that the slump, slump flow and strength of MSC initially increase and then decrease with rising SP or LP content, peaking at 10% SP and 5% LP. Compared to MSC without admixtures, 10% SP increases slump and compressive strength by 33.3% and 13.2%, while 5% LP yields respective increases of 23.3% and 7.1%. A combined addition of 10% SP and LP at a 7:3 ratio further enhances the performance of MSC, the compressive strength by 14.1%, freeze–thaw resistance by 68.4% after 50 cycles, sulfate resistance by 44.4% after 30 cycles, and shrinkage resistance by 58.9% after 90 days. SEM observations reveal that appropriate quantities of SP and LP fill internal pores, consume calcium hydroxide, and refine the microstructure, contributing to the improved compactness and durability of MSC.