Damage Process Assessment of Mortar Samples under Freeze-thaw Cycleswith Micro-CT and Expansion Measurements

Abstract

The aim of this study is to comprehensively investigate the relationship between 3- dimensional crack development and mechanical degradation during Freeze-thaw cycles (FTC). An FTC test was designed in this study to relate the micro-scale crack patterns to the macro-scale expansion and mechanical property deterioration at different FTC damage levels. Mortar specimens with waterto-cement (w/c) ratios of 50% and 75% were cast in two sizes (i.e., Ø5×10 cm, Ø2×2.5 cm) and were subjected to FTCs. For Ø5×10 cm specimens, strain in the center part of the specimens were monitored by embedded mold gauges and compression tests were conducted at different expansion levels. For Ø2×2.5 cm specimens, X-ray micro computed tomography (micro-CT) and compression tests were conducted after different FTC durations. By comparing the test results of these two groups of specimens, the expansion, mechanical degradation, and development of micro-cracks in the mortar specimens during the FTC damage process were correlated. It is indicated that with similar mechanical reduction, the damage pattern differs in two w/c cases. This research provides a test method for investigating internal swelling damage and proposes the direction for further improvement of FTC simulation model.