Measurement of the pore size distribution of geomaterials using conductometric phase transition porosimetry

In cold regions, the performance of many construction materials is highly influenced by the pore structure of these materials. The durability of aggregates, Portland cement concrete pavements, and compacted clay liners and covers are heavily influenced by the pore size distribution (PSD) of these geomaterials. Cold region phenomena such as frost heaves and frost boils are also greatly influenced by the PSD of in-situ soils. Recently, a new method for measuring the PSD of geomaterials has been developed. This method has been referred to as conductometric phase transition porosimetry (CPTP). CPTP was first introduced by Gunnink et al., 1988. With CPTP, changes in electrical conductance and temperature of saturated samples are measured during a cycle of capillary freezing and melting. These measurements are used to calculate the sample's PSD. The paper includes an introduction to CPTP, a discussion of the advantages and disadvantages of CPTP, a description of test methods and procedures that have been developed to use CPTP to measure the PSD of concrete and soil samples, and a summary of experimental test results. The test results section includes a comparison of mercury intrusion porosimetry (MIP) results with CPTP results for Portland cement mortar and compacted soil samples. It also includes results that illustrate how CPTP can be used to monitor changes in PSD that result from freezing and thawing of Portland cement concrete samples. The experimental results show that CPTP is a useful and valuable tool for quantitative studies of geomaterial pore size distributions.