New Pore Structure Assessment Methods for Cement Paste

In this study, two new approaches for pore structure assessment of cement paste are investigated and compared with mercury intrusion porosimetry (MIP)-based methods. One is based on a status-oriented computer model; the other is based on fractal analysis on the impedance measured by a noncontact impedance measurement system. In the computer model, cement paste microstructure is simulated as a function of cement properties, water-to-cement ratio (w/c), and degree of hydration. With the simulated microstructure, large capillary pores are characterized by image processing. A model developed based on nitrogen adsorption results and physical rules is applied to predict the small capillary pore structure, as a complementation to cover the whole range of capillary pores. In the impedance measurement based approach, fractal dimensions corresponding to specific pore size ranges are determined from the fractal networks and the impedance responses of the material. Then the pore size distribution curves are deduced. The former approach is capable of providing much more realistic representation of the pore structure as compared with the traditional MIP method, while the latter is also considered as a promising method for pore structure assessment, especially in large pore size range. (c) 2014 American Society of Civil Engineers.