The decomposition of tricalcium silicate in the temperature range, 1,000 degrees-1,300 degrees C

Abstract

The decomposition of tricalcium silicate, 3CaO.SiC>2, into dicalcium silicate and free lime, has been studied in the temperature region 1,000°-1,300° C. The extent of decomposition, measured by means of free-lime determinations, was found to be greatest at about 1,175° C. After a day's heating at this temperature the decomposition was about fifteen times as great as after a day's heating at 1,000° C. Above 1,175° the rate decreased rapidly, and the amount of free lime was negligible at 1,300°. The decomposition appears to be autocatalytic, the rate of the reaction being increased by the presence of either of the decomposition products, dicalcium silicate and lime. Exposure of tricalcium silicate to moist air promotes the decomposition because of the action of the moisture on the silicate, liberating lime. Freshly burned tricalcium silicate, containing a minimum amount of free lime, decomposes very slowly. The presence of gypsum accelerates the decomposition , probably because of the formation of free lime by dissociation of the gypsum. CONTENTS Page