Exploring Cementitious Additives for Pretreatment of High-Early-Strength Sewage Sludge from the Perspective of the Rapid Generation of Nonevaporable Water

Abstract

Currently, solidification/stabilization (S/S) is the most widely used pretreatment measure for sewage sludge prior to its disposal in landfills in China. Looking for an effective measure to increase the early strength of the solidified sludge has become a significant requirement for the sludge treatment market. In this study, the chemical and mechanical behaviors of the sludge samples treated by sulphoaluminate cement (SC) and ordinary portland cement (OPC) were investigated and compared by testing the nonevaporable water (NEW) and unconfined compressive strength (UCS) of the solidified sludge. This was followed by conducting scanning electron microscopy (SEM) analysis. From the perspective of the conversion of NEW, the retardation mechanisms of the hydrating reaction for the SC and OPC used in the sludge were also studied. The results showed that SC is an excellent cementitious additive with high early strength in S/S treatment for sewage sludge—much better than OPC, which is currently commonly used in sludge treatment. The UCS of the samples with a 10% mixing amount of SC and 1 day of curing can reach 50 kPa, which is the target strength for landfill disposal in China. The availability of water has proven to be a very important factor influencing the hydration of cementitious materials in sewage sludge but is usually neglected by existing studies.