Changes in microstructure and physical properties of rocks caused by artificial freeze–thaw action

Abstract

The freeze–thaw action of water inside rocks’ pores, cracks, and joints plays a dominant role in physical rock weathering where the temperature fluctuates across 0 °C. To understand this process in cold regions, artificial weathering was simulated in the laboratory. Diorite, basalt, and tuff were used as specimen, and were maintained in saturated conditions to accelerate the effect of freeze–thaw weathering. X-ray computed tomography (CT) images and scanning electron microscope (SEM) photographs were obtained to investigate changes in the inner microstructure along with repeated freeze–thaw cycles. In addition, physical properties were measured during the cycles. Particle detachment, crack initiation, and propagation and porosity increase due to volumetric expansion of water inside rocks were detected using X-ray CT and SEM. The decrease in P-wave and S-wave velocities, and in weight loss were also observed. Tuff specimens, which have low tensile strength, high porosity, and loose structure, were deteriorated rapidly, while diorite specimens on the other hand, which have high tensile strength, low porosity, and compact structure, showed relatively slight changes. The frost susceptibility of basalt specimens was found to be intermediate between tuff and diorite. The developed process for cycling and freezing set up can be useful to test the various stones in terms of frost susceptibility.