LAUSR

Abstract 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 °C, 600 °C, 800 °C or 1000 °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 post-thermal performance in HYC and its failure to collapse when water-cooled after reaching temperatures of over 800 °C were attributed to the recrystallisation of scantly hydraulic phases such as gehlenite and rankinite.