New Method for Measuring Pore Size Distributions in Concrete

Abstract

A new method for measuring the pore size distributions (PSDs) of saturated porous materials has been developed. With this new methodology, referred to as conductometric phase transition porosimetry (CPTP), the changes in electrical conductance and temperature of saturated porous materials that have been subjected to a cycle of capillary freezing and melting are measured and used to calculate PSD. Based on this methodology, a porosimeter was constructed. Methods and procedures for determining the PSD of 4‐in. (10.6‐cm) diameter by 4‐in. (10.6‐cm) high portland cement mortar and concrete cylinders are introduced. The CPTP method has been found to be free of the problems of entrapment of mercury inherent to mercury porosimetry. Also, the pressures a sample is subjected to during testing are much less than those necessary with mercury porosimetry. Therefore, deformation or destruction of pores is less. It is well known that for many geomaterials, pore structure is dependent on moisture content. With CPTP, samples do not have to be dried prior to testing as with other techniques.