Frost Resistance Test Research on Hybrid Fiber Concrete Based on Range Analysis

The research of single doped fiber concrete is relatively mature. But the research about different varieties and different geometry shape of hybrid fiber concrete was very poor. Across the research in theory, hybrid fiber concrete can improve the balance of fiber three-dimensional distribution and coordinating role of aggregate and fiber, improve the efficiency of toughening crack resistance. In this paper, through the orthogonal experiment design method for hybrid fiber reinforced concrete, the mass and compressive strength loss rate after 50 times, 75 times, 100 times freeze-thaw cycle had been studied. Use range analysis quantified the influence level of various factors on the mechanical properties. It was analyzed the hybrid fiber influence on improving the efficiency of toughening crack resistance and frost resistance. It is concluded that adding the fiber can enhance the performance of concrete frost resistance. Long steel fiber have great influence on compressive strength loss rate of hybrid fiber concrete, such as the compressive strength loss rate was reached 65.47% after 75 times freeze-thaw cycle. Short steel fiber have certain influence on mass loss of concrete which were after less freeze-thaw cycles. The influence of polypropylene fiber on concrete frost resistance increases significantly, the effect can reach 36.78% after 50 times of freeze-thaw cycle. The optimal combination of the hybrid fiber concrete ultimately determined was A2B2C3 (simultaneously mixed with 50kg/m3 short steel fiber and long steel fiber as well as 0.9kg/m polypropylene fiber). The addition of steel fiber and polypropylene fiber are both beneficial to increase the internal air content of concrete, strengthening the frost resistance of concrete. However, with the increase of dosage, the internal porosity of concrete is gradually increasing, the density is reduced, and, as a result, the corresponding increase of the compressive strength loss rate is also improved.