Durability of recycled aggregate concrete in cold regions

The combination of experimental programs and finite element numerical methods is adopted to explore the durability of WBC (waste brick concrete). Rapid freeze-thaw and flexural tests are performed with the content of WBCA (waste brick coarse aggregate) and the number of freeze -thaw cycles as variables. Freeze-thaw damage mechanisms at the microscopic interfaces of recycled concrete are revealed by scanning electron microscopy. The evolution laws of relative dynamic elastic modulus, mass loss rate, and flexural and tensile strength loss rate are analyzed. Combined with numerical simulations, the temperature stress distribution and three-point bending damage law of concrete with 100 % WBCA content at different freeze-thaw times are shown, and practical examples are verified. Results showed that WBC with high WBCA content has poor freeze-thaw resistance. Furthermore, WBC's freezing resistance and bending properties deteriorate as the number of freeze-thaw cycles increases. Possible damaged locations in the concrete are determined by stress analysis. The finite element model can predict the flexural performance of WBC better with an error of 4.5 % for the peak load and 3.5 % for the peak displacement of the beam. Therefore, the presented model can also be used to predict the performance of concrete after freezing and thawing under any WBCA replacement rate.