Chemical Reactions in hydrated Ordinary Portland Cement based on the Work by Powers and Brownyard

In a pioneering work, Powers and Brownyard (1948) were the first to systematically investigate the reaction of cement and water and the formation of cement paste. In the late 1940s they presented a thorough model of the cement paste, in which unreacted water and cement, the hydration product, and (gel and capillary) porosity were considered. Via extensive and carefully executed experiments major paste properties were determined such as the amount of retained water and the chemical shrinkage associated with the hydration reaction. These properties were furthermore related to the content of the four most important clinker phases, viz. alite, belite, aluminate and ferrite, in the cement. Locher (1975), Hansen (1986), Taylor (1997), Neville (2000) and Brouwers (2003) summarise the most important features of their work. Here, it will be demonstrated that their results enable the study of the reactions of the four clinker phases and their reaction products, which is a principal innovation. In the past, the water binding of OPC as predicted by their model has been compared to pure C3S hydration by Locher (1966) and Young and Hansen (1987). This approach is permitted, as C3S is the major constituent of OPC. The model of Powers and Brownyard (1948), however, contains valuable specific information in regard to the reaction of each individual clinker phase, such as C3S. This aspect of their model and experiments has been overlooked hitherto. This will be presented here, and will result in a new reaction model.