Effect of stone powder content on the mechanical properties and microstructure of tunnel slag aggregate-based concrete

In order to promote the resource utilization of tunnel slag and investigate the influence of tunnel slag stone powder (TSP) on the uniaxial compression performance and microstructure of concrete, the tunnel slag aggregate-based concrete with TSP content of 0%, 4%, 8% and 12% was tested and compared with natural aggregate-based concrete (NABC). The influence of TSP on workability and uniaxial compression characteristic parameters of tunnel slag aggregate-based concrete was analyzed. The results show that adding an appropriate amount of TSP (4%) can increase the slump and compressive strength of concrete. The shape of stress–strain curve of tunnel slag aggregate-based concrete is similar to that of NABC. Adding appropriate amount of TSP increases the peak stress and peak strain of concrete, and improves the toughness of concrete. TSP has weak reactivity and can react with tricalcium aluminate to produce hydrated calcium carboaluminate. The porosity of tunnel slag aggregate-based concrete is lower than that of NABC, and a small amount of TSP is added to further optimize the pore structure. TSP improves the performance of the interfacial transition zone (ITZ) of slag aggregate-based concrete by increasing the density of hydration products at the interface. This study provides a theoretical basis for the in-situ disposal of tunnel slag waste and the development of full-volume slag aggregate-based concrete.