PRETREATMENT OF HARDENED HYDRATED CEMENT PASTES FOR MERCURY INTRUSION MEASUREMENTS

Porosity is one of the major factors controlling durability and strength of hydrated cement products. A measure of pore size distribution of these materials is more definitive and can lead to a basic understanding of many phenomena occurring within the material. An accurate measurement of this is, however, difficult to obtain. Hg intrusion porosimetry to 414 MPa was used in this work to measure the pore size distribution of cement pastes prepared at water/cement ratio of 0.8, 0.6 and 0.45. Specimens were predried before intrusion measurements by several techniques including solvent replacement with methanol or isopropanol, evacuation and/or heating for various periods and conditioning at 11% RH. Second Hg intrusions were also performed to investigate the effects of first intrusion. It was concluded that it is not possible to obtain an actual pore size distribution of cement paste by Hg intrusion because of its sensitivity to stress.