A large number of studies have been conducted to investigate the pore structure of cement-based materials with the mercury intrusion porosimetry (MIP) method. However, the conventional MIP method has some drawbacks in the measurement of pore size distributions of most porous materials, including cement-based materials. This is mainly because of the lack of direct accessibility of most pore volumes. This paper reports an alternative method to investigate the pore structure with conventional MIP set-up but different testing sequence and different data analysis method. By repeating the intrusion and extrusion cycles in every pressure step, the volume of throat pores and the volume of corresponding ink-bottle pores can be determined at each pore diameter. With the assumption that the size distribution of these ink-bottle pores at each pore diameter is equal to that of the pores larger than the corresponding throat pores, the pore size distribution can be recalculated. The new MIP method is used to investigate the pore structure of Portland cement pastes. The results measured with the new MIP method are compared with those determined with conventional MIP method and backscanning (BSE) image analysis. It is found that the new and conventional MIP measurements give the same total porosity and BSE image analysis gives a relatively lower total porosity. Regardless of the curing age, the result of the new MIP method shows a critial pore diameter smaller than that of the old method and larger than that of the BSE image analysis.
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