Freezing behaviour of cemented paste backfill material in column experiments

- Cemented paste backfill (CPB) is an underground mining construction material.
- Sub-zero temperatures significantly affect CPB properties.
- Void ratio, water content and saturated hydraulic conductivity increase with decreasing temperature.
- UCS values of the CPB vary with temperature depending on the phase composition and content of the CPB material.

The behaviour of cemented paste backfill (CPB), a cementitious tailings-based construction material, when subjected to freezing in sub-zero environments is studied by means of columns experiments. A total of three columns are built and cured at specific curing temperatures of 14 °C (control), −1 °C and −6 °C for a period of 28 days. The top of the columns is left open, while the sides and the bottom are covered with a layer of thermal insulation material (fiberglass). The evolution of temperature, volumetric water content (VWC) and electrical conductivity at different heights of the column during curing are monitored. At the end of the curing, samples are taken from different heights of the columns, and then laboratory tests are conducted to evaluate their physical properties, uniaxial compressive strength (UCS) and saturated hydraulic conductivity. The obtained results show that the void ratio, water content and saturated hydraulic conductivity increase with decreasing temperature. Plotting the saturated hydraulic conductivity versus the void ratio shows that they are exponentially correlated. The UCS values of the CPB samples vary with temperature depending on the phase composition and content of the CPB material. Moreover, the results obtained indicate that the filling sequence and surface evaporation also affect the changes in the properties of CPB depending on the curing temperature. Finally, the effects of a temperature gradient found in both the longitudinal and cross sections of the column on the behaviour of CPB structures need to be carefully and comprehensively evaluated. The results presented in this study will contribute to a better understanding of the behaviour of CPB structures subjected to freezing in sub-zero environments.