GUNNAR0. ASSARSSON
328
Vol. 64
EIYDRC)TAERRfAL REACTIOKS OF CALCIUJT HYDROXIDE-Q1JARTZ AT 180-220° BY GUNNAR0. ASSARSSON Chemical Laboratory, Geological Survey, Stockholm 60, Sweden Received August d l , 1969
The phases formed a t the reaction between calcium hydroxide and quartz depend on the amount of calrium hvdroxide per unit area of grain surface, on the reaction temperature and on the period of reaction time. There are two principally different reaction ranges; within the one a monocalcium silirate hydrate (the tobermorite phase) is formed; the second one has the a-dicalrium silicate monohydrate as initial product. The concentration boundary between these ranges lies n t about 200 mg. CaOlrni.'. On extension ot the reaction time the mono- and dicalrium silicates behave :is sourre8 of calcium ions; the reactions when continued lead to a formation of new compounds poorer in lime (the 2:3-calcium silicate, the gyrolite phase), the silica ions necessary for this reaction reaching the reaction layer by diffusion from the underlying quartz surface. Secondary, accessory phases also occur (the Z-phase, the xonotlite compound). All these reactions must be referred to the slowness of the transformation reactions, rendering an observation of the reaction stages possible.
In some earlier papers the author already has given the results of some investigations on the hydrothermal reactions between calcium hydroxide and amorphous silica between 120 and 2 2 O O . l The formation of calcium silicate hydrates takes place rapidly with the production of different phases depending on the reaction time, the temperature and the vapor pressure within the autoclave. It was shown that there are distinct stages in the formation of the phases and that these stages depend on the reaction temperatures. At lower temperatures (about
