Effect of Curing Conditions on the Capillary Porosity of Hardened Portland Cement Pastes

The capillary pore structure of hardened portland cement pastes cured by high-pressure steam, chemical acceleration, high-pressure steam with reactive SiO₂, water immersion, water immersion and high-pressure steam, and hot-pressing was measured using mercury porosimetry to 50,000 psi. Differences of > 2 orders of magnitude exist in the average capillary pore diameters of the cement pastes studied. The largest pores (～1 to 3 μm in diameter) are associated with high-pressure steam-cured pastes. The smallest average capillaries observed were 0.02 μm for pastes steam-cured with reactive SiO₂. Hot-pressed pastes had essentially no porosity accessible to mercury. The application of pore size control to problems of polymer-impregnated concrete is discussed.