Resistance to freeze-thaw cycles in Canada’s climate is an important aspect of material durability. The development of a realistic experimental procedure for the simulation of this phenomenon is of great importance. Several standards are used to determine the resistance of materials to freeze-thaw cycles (ASTM C666 and D560). However, these standards do not provide confining pressure. Very few studies have been done on the influence of this parameter on resistance.
The main objective of the project is to develop an experimental device to reproduce in the laboratory the impact of freeze-thaw cycles for sol-cement mixtures subjected to a confining pressure.
The hydraulic and mechanical performance of two sand-cement mixtures (5 and 12% cement based on the dry weight of the soil) were evaluated before and after exposure to freeze-thaw cycles without confining pressure according to ASTM D560. The results show a change in hydraulic conductivity as a function of the number of freeze-thaw cycles whose tendency varies from one mixture to another. The compressive strength of the specimens of both mixtures tends to decrease after the first freeze-thaw cycles, but begins to increase after 12 cycles.
The influence of the confining pressure during the freeze-thaw cycles on the hydraulic and mechanical properties of the specimens containing 5% cement was verified with a modified triaxial cell for this project. The permeability tests do not show any interaction between the effect of the freeze-thaw cycles and the confining pressure. The confining pressure appears to affect the stress-strain behavior of sand-cement specimens by a slight shift of the deformation at peak resistance compared with the axial deformation at peak of control specimens and specimens exposed to standard freeze-thaw cycles. It appears that the sand-cement mixture recipes that were used were not sufficiently susceptible to freeze-thaw cycles to assess the influence of confining pressure. Cement hydration can also improve the performance of sandcement specimens during freeze-thaw cycles and thus eliminate the effect of confining pressure.
X-ray tomography tests were performed on the specimens of two mixtures to verify the influence of freeze-thaw cycles and confining pressure on the microstructure of soil-cement mixtures. Tomograms performed before and after freeze-thaw cycles with and without confining do not show any major changes in the pore size distribution, which tends to show that most of the hydraulic conductivity variations observed during tests permeability are due to cracking, or to the inter-variability of the specimens.
Aboud, F. (Author),
Duhaime (Supervisor) &
Dubé (Co-supervisor),
26 Oct 2018Student thesis: Master's thesis › Master in Engineering: Environmental Engineering