In the accelerated freeze-thaw test, the length and the relative dynamic modulus of elasticity sometimes changes dramatically at almost same cycle. Based on this, we proposed a new frost resistance index named the critical freeze-thaw cycle. The moisture content of concrete increases and reaches to the critical value at the critical cycle and severe damage will occur. In this paper, we examined the effect of different lowest temperature on the critical freeze-thaw cycle. Besides, the ratio of the effect with different lowest temperatures to that with -18 °C in one freeze-thaw is figured out.
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