Studies of hydrothermal reactions of UK pulverized fuel ashes. Part 1. Reactions between pulverized fuel ash and calcium hydroxide

Pulverized fuel ash/calcium hydroxide pastes (C/S ratio approximately 0.8) were autoclaved at 184 degrees C for periods up to 12 h. The pastes were an alysed for loss of calcium hydroxide and ash, release of silicon, aluminium and alkalis, and by X ray diffraction. Calcium hydroxide is consumed withi n 6 h, which coincides with the most rapid period of ash reaction. A semicr ystalline CSH phase appears initially, which converts to crystalline toberm orite at longer times. Hydrogarnet forms readily and is stable under the co nditions investigated. Differences in the behaviour of the ash samples are evident that seem to be related to the particle size distribution, rather t han to the amount of glassy phase present or to other measures of reactivit y.