A simple method of obtaining the soil freezing point depression, the unfrozen water content and the pore size distribution curves from the DSC peak maximum temperature

Abstract

A method based on measuring the maximum temperature of the peak obtained during the warming of frozen soil samples by the use of Differential Scanning Calorimetry (DSC) is proposed. The freezing point can be calculated from the peak maximum temperature by taking into account a correction due to the mass of water. The correction function can be one-time determined for a given DSC instrument and the scanning rate. The unfrozen water content curve can be determined by the transposition of variables, with the freezing point depression as the independent variable of temperature and the water content as the unfrozen water content. The method has been validated with the use of foreign results, including data from the NMR measurements. With regard to both the freezing point depression and the unfrozen water content, a very well agreement was obtained. The compatibility with the data on the freezing point depression in the Wyoming bentonite presented by Low et al. (1968) can be termed as excellent. The obtained approximation of the unfrozen water content below −5°C can be used to generate the differential pore size distribution curve (DPSD). The curves obtained in this manner are highly compatible with curves determined by the nitrogen desorption data measured at 77K with the use of the BJH method in the range of radii from 2 to 100nm.