Performance of autoclaved sludge blended cement products at elevated temperature

Abstract EN

This paper aims to evaluate the performance of autoclaved burnt sludge blended cement pastes at elevated temperatures up to 800oC.

The ordinary Portland cement (OPC) was used as blank and partially substituted by 5 %, 10 %, 15 % and 20 % burnt sludge.

The used sludge, was ignited at 850oC for 2 hours in an electric furnace.

The OPC-burnt sludge pastes were hydrothermally autoclaved at a pressure of 10 atm.

of saturated steam for 12 hours.

A study was conducted to investigate the residual physical properties of autoclaved blended cement pastes after a single thermal cycle at 100, 200, 300, 400, 600, and 800oC for 2 hours.

The hydrothermaly hardened specimens were tested for their compressive strength, hydration kinetics and the phase composition of the formed hydrates was identified.

The change in phase composition was investigated by differential scanning calorimetry (DSC) and the microstructure of scanning electron microscopy (SEM).

The results shows an increase of compressive strength of the autoclaved blended cement pastes with the exposed temperature up to 200oC and then gradual decrease up to 800oC.

It is also clear that, a recrystallization and deformation of CSH, C4AH13 and Ca (OH)2 were occurred as a result of thermal treatment .