Assessment of mechanical performance and ice content of concrete at low temperature using impact-echo method

Ice formation and its volume expansion are important causes of concrete damage in winter construction. This paper presented a non-destructive method to evaluate the strength and ice content of concrete in winter using the impact-echo method. The longitudinal wave velocity obtained by the impact-echo method was the main monitoring indicator. Firstly, the variation of wave velocity and strength of concrete under positive temperature curing and freezing conditions was studied. The influences of pre-curing time, water to cement ratio and exposure temperature on concrete were analyzed. The differences in the strength-wave velocity relationships between frozen and unfrozen concrete are revealed. Further, a quantitative method for evaluating on-site con-crete strength in winter by the impact-echo method was established. Secondly, a semi-empirical approach was proposed for calculating ice content based on wave velocity. This model provides a non-destructive way to study the freezing behavior of concrete, which is helpful for further understanding the freezing damage mechanism of concrete in the field.