Strength characteristic and micro-mechanism of organic dredged sludge solidified by cement incorporating sodium persulfate

Abstract

Cement-based solidification is a widely used sustainable technology for transforming waste dredged sludge (DS) into backfill materials. This study developed a novel solidification/oxidization synergistic (SOS) method, using Portland cement as a binder and sodium persulfate (SP) as an oxidant, for treating the organic DS with different fulvic acid (FA) content. The results demonstrated that adding SP could significantly improve the UCS of the cement-solidified DS doped with FA. When the FA content was 4%, the 28-day UCS of the sample with 25% cement content was only 160.5 kPa. The addition of 6% SP increased the UCS to 2225.5 kPa, which was 15.1 times that of the sample without SP. However, excessive SP hydrolyzed to produce a large amount of sulfuric acid, leading to a low pH value of the pore solution. This in turn hindered further persulfate activation and cement hydration, which was detrimental to the strength of cement-solidified DS.