DETERMINATION OF PORE CONNECTIVITY BY MERCURY POROSIMETRY

The injection of mercury into a porous structure and the subsequent withdrawal of the liquid from the system can provide information on the geometry and topology of voids or pores within the material. A three-dimensional, spherical random network has been developed to investigate the effects of pore size distribution and pore connectivity on the features of mercury porosimetry experiments. The inherent flexibility of the model facilitates the construction of networks with varying connectivities or distributions of connectivities. The extrusion algorithm used in the simulations has been selected from a number of alternative mechanisms by comparing each mechanism with previously reported experimental data from glass networks. The results from simulations of standard intrusion-extrusion cycle porosimetry experiments suggest that there is a characteristic entrapment of mercury for a network comprising a Gaussian pore size distribution. This entrapment is dependent on sigma/mu, where sigma is the standard deviation of the distribution and mu is the mean pore size. The intersection of a measured quantity of entrapped mercury with the characteristic entrapment function yields two estimates of pore connectivity for the model network. A new pressure sequence for mercury porosimetry is introduced to generate further information on pore topology. The mini-hysteresis loops produced by this pressure sequence provide the information which distinguishes between the two possible values of connectivity for the network structure and allow a more accurate determination of the characteristics sigma and mu for the pore size distribution. The simulations thus show that it is possible to infer the pore connectivity for a network model by combining the wealth of information that can be generated by various pressure sequences in a porosimetry experiment.