Abstract: Based on series of laboratory tests including cyclic freeze-thaw, water immersion and cyclic drying-wetting, an experimental study has been performed to analyze the intrinsic change in the compressive strength and appearance of dredged sludge solidified with reactive MgO-fly ash, a green and environmental-friendly binder, and clarify the climate change-induced durability evolution. The test results indicate that the dredged sludge solidified with reactive MgO-fly ash has outstanding performance in resisting the damage from cyclic freeze-thaw, water immersion and cyclic drying-wetting. The durability performance of reactive MgO-fly ash solidified sludge is significantly enhanced as the MgO-fly ash content and mass ratio of MgO to fly ash increase. The strength behavior of MgO-fly ash solidified sludge is largely weakened by water immersion, cyclic dry-wet and cyclic freeze-thaw, and this causes a smaller compressive strength than that of samples cured under standard condition. As the number of freeze-thaw cycle increases, the compressive strength tends to decrease gradually. The compressive strength of samples immersed in water is initially reduced, and then changes within a limited interval. The compressive strength of damaged samples decreases with the increasing drying-wetting cycles. Based on the test results, an intrinsic microscopic mechanism model is proposed for the durability evolution of dredged sludge solidified with reactive MgO-fly ash.

Key words: sludge, reactive MgO-fly ash, solidification, compressive strength, durability