Hydration of Highly Pure Magnesia Clinkers and Electrically Fused Magnesia Grains

Abstract

Hydration was studied for highly pure magnesia clinkers and also for electrically fused magnesia grains with an aid of autoclave.This autoclave was specially designed to prevent the samples from immediate contact with liquidus water.Uniform magnesia hydroxide layer was clearly observed on the surface of both clinkers and grains.The hydration process of these grains was considered essentially to be consisted of the hydration itself and the followed disintegration. The hydrated samples were sieved into four fractions for the analysis of the hydration rate of these grains in order to eliminate the influence of the disintegration. The weight gain of each fraction by the hydration was calculated on the basis of the value of the ignition loss.The weight gain was almost rationalized by a linear function of the reciprocals of the grain diameter. The initial rate of the layer growth of the magnesium hydroxide showed a proportional relation to the hydration time. Under a special hydration condition contacting the samples with liquidus water, the disintegration was promoted for the highly pure clinkers, and depressed for the electrically fused grains. The CaO/SiO2 ratio contained in the clinkers affected remarkably the hydration.