Cold isostatic pressing of cement pastes to produce pore reduced cement (PRC)

In this paper we extend the method of cold isostatic pressing from the usual dry powders to water-saturated pastes. As an example, immature Portland cement paste, initially prepared under normal conditions of mixing and casting (high shear mixing of paste at water/cement ratio of 0.3), has been cold isostatically pressed to produce pore reduced cement (PRC). The combined pressing of paste and the removal of fluid is the basis of the PRC technique. The design of the tooling for isostatic pressing is very important and several sample tooling designs were tested to optimise the in-situ removal of fluid from the compressed paste. Pressed samples were characterised in terms of density, microstructure and mechanical performance after selected post-pressing curing times. Their properties were correlated with pre-curing time and rate of pressurisation. Comparisons are made with pastes prepared using a unidirectional pressing geometry permitting discussion of potential limitations of the pressing technique. (C) 1998 Elsevier Science Limited. All rights reserved.