Abstract
The deterioration of the physical and mechanical properties of tonalites subjected to freeze‐thaw cycling under three different temperature ranges was explored using several experimental techniques. Uniaxial compression and three‐point bending tests were conducted on untreated and treated tonalite specimens. Clear decreases in uniaxial compressive strength (UCS), Young’s modulus, and fracture toughness were observed in tonalite specimens with frost damage. Although Young’s modulus and fracture toughness did not show clear decreases as the minimum temperature of the freeze‐thaw cycle decreased from −30°C to −50°C, the UCS decreased almost linearly. The macromechanical characteristics of the tonalites can be explained by changes in mineral content and microstructure. The intensity of X‐ray diffraction (XRD) peaks of minerals in tonalites that had not been freeze‐thaw cycled were approximately 10 to 20 times higher than the peaks for the specimens subjected to freeze‐thaw cycling, implying that the internal structure of tonalite is less compact after frost damage. The microstructures of the tonalite specimens were also examined using scanning electron microscopy (SEM). Increased amounts of fragmentation and breaking of structural planes were observed as the minimum temperature of the freeze‐thaw cycle decreased.
Highlights
Weathering, for example from frost damage, heat exposure, or chemical processes [1,2,3], is common in nature. e deterioration of rocks due to weathering has recently attracted increasing concern from both academic researchers and engineers
Most of the research has employed freezing and thawing times of 4 hours each, which we follow here. e tonalite specimens were placed in a WGD-501 freeze-thaw device and subjected to freeze-thaw cycling. e specimens were divided into three groups: in all cases, the identical maximum temperature (20°C) was used, but minimum temperatures varied between groups (−30°C, −40°C and −50°C). e temperature settings used during freeze-thaw cycling are shown in Figure 6. ere
Physical and mechanical property data obtained from uniaxial compression testing, three-point bend testing, and elastic wave velocity measurements were analysed and compared with the results of mineral composition and microstructure investigations obtained from X-ray diffraction (XRD) analysis and microscopy
Summary
Weathering, for example from frost damage, heat exposure, or chemical processes [1,2,3], is common in nature. e deterioration of rocks due to weathering has recently attracted increasing concern from both academic researchers and engineers. X-ray CT imaging has been used to measure crack openings [29, 30], but to date, there has been limited research into changes in the microstructure and mineral composition of rocks subjected to freeze-thaw cycling. E main objective of this research is to investigate the deterioration of physical and mechanical properties of tonalite resulting from freeze-thaw cycling under di erent temperature ranges. To this end, uniaxial compression and three-point bending tests were conducted on tonalite specimens, and XRD and SEM were used to explore changes in mineral composition and microstructure resulting from freeze-thaw cycling.
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