Mechanical properties of polypropylene fiber-cement stabilized dredged sludge under low-salinity dry-wet cycles

Cement stabilization enhances dredged sludge utilization but often suffers from poor durability and high carbon emissions. Polypropylene fibers-cement (PFC) stabilization has emerged as a promising alternative to improve mechanical properties. Nevertheless, the long-term performance under low-salinity dry-wet cycles remains poorly understood. This study investigates the evolution of mechanical properties in PFC-stabilized sludge under such conditions. The results show that PFC significantly enhances unconfined compressive strength (UCS), with an increase of up to 45.4 % for 3-day-curing specimens, while also improving ductility and crack resistance through fiber bridging. During dry-wet cycling, the UCS initially increased, peaking at the sixth cycle (34.7–154.1 % higher than the initial value) and remained higher than that of non-cycled samples even after 15 cycles. The low-salinity conditions promoted early strength development, leading to an earlier peak (cycle 6) compared to freshwater conditions (cycle 9), but could not prevent the progressive deterioration under prolonged cycling. Extended curing (≥ 7 days) significantly enhanced the resistance to degradation and reduced mass loss. These findings confirm that PFC stabilization effectively improves both early-age and long-term performance of dredged sludge under fluctuating moisture conditions, providing a valuable strategy for its durable and sustainable reuse in coastal geotechnical engineering. • Polypropylene fibers enhances UCS of cement-stabilized sludge via fiber bridging. • Under dry-wet cycles, UCS peaks at cycle 6 before gradual decline. • PFC-stabilized sludge maintains higher strength than non-cycled soil after 15 cycles. • PFC stabilization provides both early strength and long-term durability.