Mechanical property, sorptivity and microstructure of steam-cured concrete incorporated with the combination of metakaolin-limestone

To explore the feasibility of using metakaolin and limestone in steam-cured concrete, mechanical property, sorptivity and microstructure of steam-cured concrete incorporated with the combination of metakaolin-limestone powder were studied, with steam-cured concrete incorporated with ground granulated blast furnace slag and fly ash as a reference. Due to the high reactivity of metakaolin, the presence of metakaolin reduces the heterogeneous distribution of hydration products, thereby resulting in a refined microstructure and lowered sorptivity of steam-cured concrete. The synergistic effect of metakaolin with limestone powder leads to further improvements on strength, sorptivity associated with a more uniform microstructure at late ages. Moreover, concrete incorporated with metakaolin-limestone powder and steam-cured at 40 °C can gain a comparable early strength (1 day) with concrete incorporated with the combination of ground granulated blast furnace slag - fly ash, and steam-cured at 60 °C; this indicates that the incorporation of metakaolin enables to reduce steam curing temperature without compromising early strength gain, which is of significance for mitigating steam-curing induced detrimental effects and reducing energy consumption.