Desulfurization Ash Recycling in the Cement-Stabilized Sludge and Its Abnormal Efficiency

The disposals of dredged sludge (DS) and desulfurization ash (DA) are both increasingly challenging due to land occupation and environmental pollution. This study investigated the strength development and mechanism on DA incorporation in the cement(C)- stabilized DS. Unconfined compressive strength (UCS) tends to increase firstly and then decrease with the increase of DA/C ratio, where the highest strength achieves at DA/C ratio equal to 20%. The liquid limit (LL) and plasticity index (PI) significantly decrease with the DA incorporation, suggesting that the DA can suppress the adsorbed water film of clay minerals and can also act as a retarder to delay the initial setting time. It inspires the introduction of vacuum dewatering method to squeeze out free water and to enhance the strength. A suitable DA combined with the vacuum dewatering method can significantly reduce the porosity and enhance the strength of CDS.