Hydrothermal reactions between lime and aggregate fines*

Hydrothermal reactions between lime and aggregate such as pulverized fuel ash, expanded colliery shale, ground quartz, granulated and foamed blastfurnace slag have been studied. The compressive strength and mineralogy have been determined for various mixtures of lime and aggregate fines autoclaved at 160 lb/in² for 2,6,16 and 48 hours. The cementitious minerals identified were: tobermorite (calcium silicate hydrate) and a hydrogarnet when the aggregate was pulverized fuel ash or shale; tobermorite and zonotlite when it was quartz; and poorly crystalline tobermorite (tobermorite gel), dicalcium silicate alpha-hydrate and a hydrogarnet when the aggregate was slag glass.

When dicalcium silicate alpha-hydrate was the predominant phase, the strength of the blocks was lower than when tobermorite was the main phase.