A simple method for determining the total amount of physically and chemically bound water of different cements

For Portland cements, Powers' model provides a simple method for calculating the total amount of water bound by cement hydration (both physically and chemically bound). On the other hand, no such simple model is available for other types of cements that are of increasing interest, such as calcium aluminate cements and calcium sulfoaluminate cements. The main uncertainty for these types of cement regards the amount of physically bound water in the hydrates, while the amount of chemically bound water can be calculated, e.g., by thermodynamic modeling. In this paper, a simple approach for estimating the total amount of bound water of different cements is presented. This novel approach consists in measuring the rate of heat liberation of cement pastes made with the same cement, starting at low water-to-cement ratio (w/c) and increasing it steadily. As the cumulative heat of hydration reaches a plateau for a given w/c and does not increase for further increases in the water amount, this w/c is interpreted as total water demand of the cement. The method is tested with a Portland cement, showing that it is in broad agreement with Powers' model. First results for calcium aluminate cement and calcium sulfoaluminate cement are presented, from which estimations of the amount of physically and chemically bound water are obtained.