Strength and compressibility of cement-stabilized sludge under low-salinity dry-wet cycles: effects of cycle number and curing duration

The reuse of dredged sludge as construction fill is constrained by poor durability under cyclic environmental exposure. While cement stabilization improves engineering performance, the behavior of cement-stabilized sludge under low-salinity dry-wet cycles remains underexplored. This study investigated the strength, compressibility, and microstructural evolution of cement-stabilized sludge subjected to site-specific low-salinity cycles, for curing durations of 3–14 days. Results revealed a two-stage response: initial strength enhancement (≤6 cycles) followed by progressive degradation. Three-day curing yielded a 52% UCS increase but a 56% loss after 15 cycles, whereas ≥7 days curing improved durability by limiting strength loss, mass loss, and void ratio growth. Microstructural evidence indicated that extended curing promotes denser calcium silicate hydrate networks, reduces pore connectivity, and delays crack propagation. A comparison between site water and treated freshwater showed similar behavior under dry-wet cycles. These findings highlight the need for adequate curing to ensure durable reuse in low-salinity environments.