Research of Phase Transitions Pore Solutions of NaCl and CaCl2 on a Differential Scanning Calorimeter DSC

Abstract

At negative Celsius temperatures the phase composition of pore water determines the whole spectrum of rocks’ and construction materials’ properties. It has a dominant role in the physical, chemical and mechanical processes which take place in them. The paper presents some results of the phase transitions study of pore solutions in a variety of soils over a wide range of negative temperatures. The studies of NaCl, CaCl2 pore solutions phase transitions in sand, loam and clay were carried out using a differential scanning calorimeter DSC L63. The concentration of NaCl and CaCl2 solutions varied from 5 to 20%. The samples were cooled down from a room temperature to an initial temperature of -100°C at the rate of 5 °C/min. After being kept at an initial temperature for 30 min, the samples were heated to 10°C at the rate of 2°C/min. The studies confirm the complex nature of the influence of rock’s hard skeleton onto the phase equilibrium conditions of the pore solution, and show the need for detailed studies of the saline soils phase composition in each particular case. It is shown that rock’s hard skeleton and solutes are the factors influencing the shift of the eutectic temperatures, which depends on the dispersion of the hard skeleton and pore solution concentration.