Mechanical properties and damage modeling of hybrid fiber reinforced concrete under freeze-thaw cycles

This study aimed to investigate the mechanical properties of steel-polyacrylonitrile hybrid fiber reinforced concrete (SPHFRC) and its durability under freeze-thaw damage. Firstly, the mechanical properties of hybrid fiber reinforced concrete (HFRC) were studied by compressive strength and flexural strength tests. Secondly, with the help of rapid freeze-thaw test, the variation rules of mass loss rate and relative dynamic elastic modulus were characterized. Based on the test results and freeze-thaw damage theory, the evolution equation of freeze-thaw damage of hybrid fiber reinforced concrete (HFRC) based on Weibull distribution was established. The results show that the enhancement effect of hybrid fiber on the mechanical strength of concrete is better than that of single mixed fiber, especially in the improvement of flexural strength; Accordingly, compared with the single mixing of steel fibers or single mixing of polyacrylonitrile fibers, hybrid fibers are more effective in improving the durability of concrete against freezing and this improvement effect increases with the increase of steel fiber content; The freeze-thaw damage model of Weibull distribution can better reflect the freeze-thaw damage process of hybrid fiber reinforced concrete (HFRC) .Through the freeze-thaw damage evolution curve, it can be found that after 500 freeze-thaw cycles(About 70 years of concrete life in northern China), the freeze-thaw damage degree of the hybrid fiber reinforced concrete (HFRC) with different steel fiber content has been very close, which means that the influence of steel fiber content on the freeze-resistant performance of hybrid fiber reinforced concrete (HFRC) will be limited. This study provides a theoretical basis and technical basis for the design of concrete structures in alpine regions.