Microstructural characterisation of hybrid cement after exposure to high temperatures

This study was designed to determine the mineralogical and microstructural changes taking place in a hybrid alkaline cement (HYC = 30% Portland cement clinker + 70% (slag + fly ash + alkaline activator)) exposed to high temperatures. The cement pastes were heated for 2 h at 400 degrees C, 600 degrees C, 800 degrees C or 1000 degrees C and subsequently air- or water-cooled. Their mechanical strength was determined after cooling. The HYC pastes had higher residual strength than the reference porland cement (OPC). That better postthermal performance in HYC and its failure to collapse when water-cooled after reaching temperatures of over 800 degrees C were attributed to the recrystallisation of scantly hydraulic phases such as gehlenite and rankinite. (C) 2020 Elsevier Ltd. All rights reserved.