The influence of pozzolanic materials on the mechanical stability of aluminous cement

Abstract High alumina cement paste, in the presence of silica fume, shows an increasing strength trend even at 20 °C and 40 °C, since this pozzolan causes the formation of gehlenite hydrate (C 2 ASH 8 ) and therefore strongly reduces the transformation of hexagonal aluminate hydrates (CAH 10 , C 2 AH 8 ) into the cubic hydrate (C 3 AH 6 ) which is responsible for the strength loss of high-alumina cement mixes at higher temperatures (> 20 °C). On the contrary, fly ash is not suitable for reducing the transformation of hexagonal hydrates into the cubic phase. Consequently, the strength at 20 °C and 40 °C of the fly ash-high alumina cement mixes decrease as well as the high alumina cement pastes in the absence of pozzolan.