Estimating the permeability of cement pastes and mortars using image analysis

8 A method to estimate permeability of cement-based materials using pore areas and perimeters from SEM images 9 is presented. The pore structure is idealised as a cubic lattice having pores of arbitrary size. The hydraulic con10 ductance of each pore is calculated using the hydraulic radius approximation, and a stereological factor is applied 11 to account for the random orientation of the image plane. A ‘constriction factor’ is applied to account for varia12 tions in pore radius along the pore axis. Kirkpatrick’s effective medium equation is then used to obtain an effec13 tive pore conductance, from which the macroscopic permeability is derived. The method was tested on forty-six 14 pastes and mortars with different w/c ratio, cement, age and sand content. The permeabilities ranged from 3×10 15 18 m to 5.8×10 m. It was found that 76% of the permeabilities were predicted to within a factor of ±2, and 16 98% within a factor of ±5 from measured values. 17