Differential thermal method of estimating calcium hydroxide in calcium silicate and cement pastes.pdf

CEMENT and CONCRETE RESEARCH. Vol. 9, pp. 677-684, 1979. Printed in the U.S.A 0008-8846/79/060677-08502.00/0 Copyright (c) 1979 Pergamon Press, Ltd. DIFFERENTIAL THERMAL METHOD OF ESTIMATING CALCIUM HYDROXIDE IN CALCIUM SILICATE AND CEMENT PASTES V.S. Ramachandran Division of Building Research National Research Council of Canada Ottawa, Canada (Communicated by P.J. Sereda) (Received July 30, 1979) ABSTRACT DTA is applied to estimate Ca(OH) 2 in cementltlous phases by determining the peak areas caused by the decomposition of Ca(OH) 2 to CaO+H20. In the hydration of C3S generally, the chemical method yields slightly hiEher values. DTA is also used as a monitoring technique in preparing a practically Ca(OH)2-free product from hydrated portland cement or hydrated C3S. Hydrated portland cement or C3S has now been exposed to an unsaturated Ca(OH) 2 solution and extraction continued until the sample indicate no endothermal peak for Ca(OH) 2. The thermal method permits determination of the rate of formation of Ca(OH) 2 in portland cement hydrated in the presence of 0, i, 2 and 3} per cent CaC12. Lauteur utilise la technique thermique diff~rentielle pour ~valuer la teneur en Ca(OH) 2 des phases liantes en d~terminant les secteurs pics causes par la d~compositlon du Ca(OH) 2 en CaO + H20. Pour lhydratation du C3S, la m~thode chimique donne g~n~ralement des valeurs l~g~rement plus ~lev~es. La m~thode thermique dlff@renLielle sert aussi de technique de contrSle dans la pr~paratlon dun prodult pratlquement exempt de Ca(OH)2 ~ partir de ciment portland ou de C3S hydrate. Lauteur expose du ciment portland ou du C3S hydrat~ ~ une solution de Ca(OH)2 non satur~e et continue 1extraction jusqu~ ce que l~chantillon ne produ/se plus de pics endothermlques en pr@sence de Ca(OH) 2. La m~thode thermique permet de d~terminer la vitesse de formation du Ca(OH)2 dans le ciment portland hydrat~ en presence de 0, i, 2 et 3} pour cent de CaCI 2 . 677 678 Vol. 9,