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

We developed a mercury intrusion porosimetry (MIP) simulator that takes int o account the hierarchical structure of the porosity in certain materials ( e.g., cement paste). We show that pore diameters indicated by the MIP resul ts 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 in terpret experimental data obtained for cement pastes with and without a rea ctive 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 varianc e with the Powers-Brownyard model of hydration. Our experimental results ar e in accordance with observations that the hydration process fixes the morp hology of the hydration product. This morphology does not evolve continuous ly with w/c, only with the fraction of C-S-H corresponding to a given morph ology evolves. (C) 2000 Elsevier Science Ltd. All rights reserved.