Using strain to evaluate influence of air content on frost resistance of concrete

In order to ensure proper frost resistance, a design of artificial air-void system with defined geometric structure is needed in concrete. Strain, which may have certain inherent advantages compared to traditional test parameters, such as real-time nondestructive monitoring, more accurate and continuous with little error that is caused by manual intervention and so on, was used to evaluate influence of air content on frost resistance of concrete in this study. With the process of freeze-thaw cycles, the moving up strain hysteretic loop indicates that the continued accumulated and irreversible residual strain is generated in the concrete matrix. The residual strain values of concrete with more air content (4.5% and 6.9%) are obviously lower, indicating that their deformation and freeze-thaw damage degree are smaller. And not only that, residual strain is able to reflect some information of concrete early frost resistance, owning its special advantage compared with traditional parameters. Besides, the variation of freeze characteristic temperature ∆Tf and the variation of apparent frost heaving coefficient ∆αf defined in this study are able to characterize the freeze-thaw damage degree and frost resistance of concrete respectively.