Effect of some admixtures on the surface properties of the hydration products of silica fume/Ca(OH)(2) mixtures

The effect of sodium naphthalene formaldehyde sulphonate polycondensate and stearic acid on the surface properties of calcium silicate hydrates, forme d as a result of the hydration reaction between silica fume and calcium hyd roxide, has been examined by the use of low-temperature nitrogen gas adsorp tion techniques. In addition, the interaction of such admixtures with the c alcium silicate hydrates formed was investigated by infrared (IR) spectrosc opic analysis. It was observed that both admixtures increased the specific surface area of the calcium silicate hydrates quite considerably relative t o the behaviour of a blank sample (i.e. without addition of admixture), esp ecially during the initial stages of hydration (after 24 h). IR examination demonstrated that the admixtures used did not interact chemically with the calcium silicate hydrates although physical interaction was possible.