EFFECT OF SOME INORGANIC ADMIXTURES ON THE FORMATION AND PROPERTIES OF CALCIUM SILICATE HYDRATES PRODUCED IN HYDROTHERMAL CONDITIONS

Hydrated calcium silicates have been synthesized at 200 degrees C unde r saturated steam pressure, giving materials consisting of ill crystal lized calcium silicate hydrates, formed as an initial product and/or m ore crystalline forms. Three series of samples having different CaO/Si O2 ratios and doped with inorganic compounds such as CaCl2, AlCl3, CrC l3, Na2CrO4, NaOH and Al(OH)(3) were produced. The phase composition o f the samples was examined by XRD. The microstructure was observed wit h the SEM and porosity measurements. Their thermal behaviour was chara cterized by DTA/TG methods. It has been found that the CaO/SiO2 loweri ng promoted the formation of poorly crystalline C-S-H with high surfac e area and porosity. The stabilizing effect of Al on tobermorite was g enerally confirmed. The formation of disordered C-S-H, with relatively high water content, surface area and porosity in the presence of CrCl 3 was found. The formation of xonotlite was promoted by CaCl2 and NaOH . Copyright (C) 1997 Elsevier Science Ltd.