建設材料 塩化カリウムを添加したエーライトの水和反応と強度発現

Abstract

The chlorides by-pass process has been introduced to many cement plants in recent Japan, because of the increase of chloride content in cement raw materials when municipal wastes are used. The extracted dusts called bypass dusts, containing potassium chloride as the main component were formed in this process. It is necessary to utilize this byproduct; otherwise it will become new industrial waste. This paper discusses the influence of potassium chloride on the hydration of alite, the main component of portland cement, by means of XRD quantitative analysis to determine the phase composition of hydration products. And, the relations between pore structures and compressive strength of hardened pastes with or without potassium chloride has also been investigated.The compressive strength was decreased with the increasing quantity of potassium chloride after the hydration of 7 days. The strength decreased remarkably by the addition of the potassium chloride at 28 days hydration. The dependence of the strength on the porosity of hardened pastes with potassium chloride was larger than without potassium chloride. And the porosity of hardened paste with potassium chloride became larger at the same hydration ratio of alite. Then, the amounts of produced calcium hydroxide were decreased at the same hydration ratio of alite, by the addition of potassium chloride, and Ca/Si ratio of calcium silicate hydrate was increased. It is conceivable that the above mentioned difference of hydration products influences the microstructure and the strength characteristics of the hardened alite paste with or without potassium chloride.