Utilization of lime/carbide slag-activated ground granulated blast-furnace slag for dredged sludge stabilization

Abstract

This study investigated the feasibility of using lime (L) and carbide slag (CS) to activate ground granulated blast-furnace slag (GGBS), as a potential substitute to Portland cement (PC) for stabilizing dredged sludge (DS). A series of unconfined compressive strength (UCS), scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests were performed to evaluate the strength development and micro-mechanisms of stabilized DS. The results showed that the optimum lime content was 20-25% for L-GGBS stabilized DS, which can achieve the highest UCS. The 28-, 60- and 90-day optimum UCS of stabilized DS with 20% L-GGBS were 1.38, 1.14 and 1.06 times that of 15% PC stabilized DS. Similarly, the optimum CS content of 25-30% was recommended for achieving the highest UCS of CS-GGBS stabilized DS. The 28-, 60- and 90-day optimum UCS of 20% CS-GGBS stabilized DS were 1.45, 1.12 and 1.02 times that of 15% PC stabilized DS. It was suggested using 20% L-GGBS or CS-GGBS instead of 15% PC for stabilizing DS. The SEM and XRD results revealed that the CSH and CAH gels were the main hydration products for stabilized DS, and the ettringite was also obviously detected in CS-GGBS stabilized DS.