<p>In areas with complex terrain, tunnel excavation provides a strong guarantee for the construction of traffic engineering. However, a large amount of tunnel slag (TS) waste is generated during tunnel excavation, which seriously affects the local environment. Crushing waste slag into aggregate to produce concrete for tunnel construction is an eco-friendly and low-cost way. However, stone powder (SP) is often attached to the aggregate surface, which has a significant influence on the performance of concrete. Therefore, this study investigates the effect of stone powder content on the long-term volumetric stability and microstructure of concrete. The results show that the addition of a small amount of SP is beneficial to improve the fluidity of the mortar due to the increase of the binder content. Meanwhile, excessive SP reduces the fluidity of the mortar, which benefits from the increase of plastic viscosity and yield stress. Slag aggregate-based concrete exhibits lower shrinkage deformation relative to natural aggregate concrete, and the shrinkage deformation of concrete increases with increasing SP content. Although the incorporation of SP reduces the total hydration exotherm of the paste due to dilution effect, its nucleation and micro-water absorption shortens the end time of induction and acceleration phases of the paste. In addition, adding proper amount of SP increases the content of hydration products, and SP and cement paste generate calcium aluminate hydrate. The slag aggregate has a more irregular shape, which allows it to bond tightly to the cement matrix. This study provides a sustainable path for the construction of tunneling projects in remote areas.</p>