Pore Structure and permeability of hardened cement paste

Synopsis A review of the literature on flow through porous media suggests that the permeabilityof hardened cement paste should be related to pore size distribution, pore conductance, tortuosity and isotropy. It is likely that these factors do not exhibit a unique value. Tests were made on OPC and OPC/pfa pastes cured for I, 4 and 12 weeks in Ca(OH)2, solution. The permeability of both types was similar for those pastes cured for 4 and 12 weeks at 35°C, whilst after one week's curing the OPC/pfa paste was sign$cantly the more permeable. Pore size distribution was determined by using a two-stage mercuryintrusion technique. A simple model, based upon Poiseuille's formula, was developed and shown to yield a reasonable correlation with the experimental determination of permeability for the OPC pastes and on SRPCpaste cured for 4 weeks. The correlation was not so goodfor the OPC/pfa pastes, probably as a consequence of structural damage during mercury intrusion in such pastes.