Mercury intrusion porosimetry and hierarchical structure of cement pastes -: Theory and experiment

We developed a mercury intrusion porosimetry (MIP) simulator that takes into account the hierarchical structure of the porosity in certain materials (e.g., cement paste). We show that pore diameters indicated by the MIP results depend not only on the pore size distribution in the sample, but also on the connectivity of the pore space. On the basis of our simulations, we interpret experimental data obtained for cement pastes with and without a reactive admixture. The MIP data show that the capillary porosity fur the pure paste is connected, even for the water/cement ratio w/c = 0.30, at variance with the Powers-Brownyard model of hydration. Our experimental results are in accordance with observations that the hydration process fixes the morphology of the hydration product. This morphology does not evolve continuously with w/c, only with the fraction of C-S-H corresponding to a given morphology evolves. (C) 2000 Elsevier Science Ltd. All rights reserved.