Influence of sandstone sand manufactured by excavated waste on properties of cement mortar

Construction and urbanization are causing a worldwide shortage of river sand, and alternative resources should be explored. Depending on global storage and the proportion of excavated construction waste, sandstone waste from underground engineering is considered for producing manufactured sand (MS). The lithology and waterrock interaction of sandstone raise concerns regarding its suitability as a MS resource. Therefore, in this research, manufactured sandstone sand (MSS) is examined, which is produced by crushing dry and saturated sandstone waste with a washing or sieving process for powder removal. The performance of cement mortar is evaluated by studying the workability, mechanical properties, and microstructure with 0, 30%, 50%, and 70% replacement ratios of MSS. The workability of fresh mortar is primarily affected by the stone powder content, whereas the roundness and surface roughness of MSS exert a minimal influence. The compressive strength of mortar does not consistently decline with increasing MSS replacement ratio, as expected. In all groups of mortar, the compressive strength with 70% replacement is slightly higher than that with 50% replacement. The flexural strength of mortar is almost unaffected by MSS replacement. The maximum decrease in the flexural strength is only 4.9% relative to the control group. In this study, a mercury intrusion porosimetry test is also conducted, and a multiscale model is introduced to explain the abovementioned nonmonotonic effect of the MSS substitution on the compressive strength of mortar. The results suggest both a feasible performance and optimal utilization of MSS.