The work of Powers and Brownyard revisited: part 1

Powers and Brownyard [Studies of the physical properties of hardened Portland cement paste. Bull. 22, Res. Lab. of Portland Cement Association, Skokie, IL, U.S. J. Am. Concr. Inst. (Proc.), 43 (1947) 101–132, 249–336, 469–505, 549–602, 669–712, 845–880, 933–992 (reprint)] were the first to systematically investigate the reaction of cement and water and the composition of cement paste. They introduced the concept of nonevaporable (water retained in P-dried state) and gel water (additional water retained upon saturation). Their specific volumes (νn and νg) are lower than that of free water, causing chemical shrinkage. The retained water was furthermore related to the content of the four most abundant clinker phases, viz alite, belite, aluminate and ferrite. Their work is recapitulated here. Major aspects, such as the specific volume of nonevaporable and gel water, are addressed, as well as the issue of gel water being “compressed”. Subsequently, it will be demonstrated that their water retention data enable the study of the molar reactions of the calcium silicate phases and the reaction products C-S-H (C1.7SH3.2 when saturated) and CH, which represents a principal innovation. Using the molar reactions and the specific volumes of nonevaporable (νn) and gel water (νg), the density of saturated C-S-H and its porosity are derived.