Phosphorus Tailings Sand Synergized with Multiple Solid Wastes for the Preparation of Cementitious Materials: Properties and Mechanisms

In this study, phosphorus tailings sand (PTS) was ground into fine powder and incorporated with slag and fly ash to formulate a cementitious material composed solely of solid wastes. The current research aimed to promote the high-value utilization of local solid waste resources in Lianyungang and to explore their potential application in soil stabilization and ground improvement. Through optimization of component dosage and the proportions of alkaline activators, the effects on workability, mechanical properties, drying shrinkage, wet–dry cycles, microstructural evolution, and heavy-metal leaching behavior were comprehensively examined. The findings revealed that at the optimal ratio of PTS–slag powder–fly ash = 5:2.5:2.5, the developed cementitious material demonstrated a 28-day compressive strength of 33.8 MPa, along with 4.5 MPa flexural strength, and 168 mm flow spread. Moreover, the 28-day drying shrinkage reached a minimal value of 0.038%, with reduced mass loss of 6.7% after wet–dry cycling. Furthermore, under non-freezing conditions, the leaching content of Zn, Mn, Pb, and Cu from the PTS-based multi-solid-waste cementitious system remained below the permissible limits for non-hazardous discharge established by Chinese environmental regulations. These findings provide an innovative pathway for the resource-efficient application of phosphorus tailings sand and several solid wastes while offering technical guidance for silt stabilization and ecological restoration efforts in the Lianyungang region, highlighting promising engineering application prospects.