Abstract

Ceramic Sintered Sludge Ash (CSSA) has garnered a great attention for its potential to mitigate CO2 emissions by its replacing into cement. This study investigates the consequential changes in the properties of cement paste blended with CSSA. Laboratory tests indicated that the high specific surface area of CSSA was the essential factor contributing the increase of water of consistency and the delaying of setting time. In terms of strength, the CSSA affected the cement paste to a greater extent after 3 days of hydration than at 28 days. The inert hydration components as quartz and feldspar in CSSA may be responsible for the observed early hydration retardation. During 28 days of hydration, physical and mechanical properties were employed to quantify Ca(OH)2 content and the degree of cement hydration. The participation of CSSA in the pozzolanic reaction could additionally produce calcite, which promoted hydration and improved the strength of cement paste up to 90 days. Scanning electron microscopy (SEM) revealed that amorphous hydration products, CSHs and Ca (OH)₂ covering the CSSA surface, were observed forming a robust structure due to normal hydration and pozzolanic activity of CSSA.

Keywords:Ceramic sintered sludge ash; Cement paste; Consistency; Setting; Water absorption; Density; Porosity; Strength; Free lime; Heat of hydration; SEM