The fracture behavior of concrete with steel and macropolypropylene hybrid fiber blends (HyFRC) is evaluated and compared with steel fiber reinforced concrete (SFRC). Fiber blends at identical volume fraction as SFRC are shown to produce an improvement in the fracture response. At small crack separation, immediately after cracking, higher cohesive stress is produced in HyFRC compared to SFRC. Polypropylene fibers in concrete contribute cohesive stresses at larger crack separation. Polypropylene fibers in the concrete matrix improve the efficiency of the steel fibers by mobilizing a higher resistance at the initiation of the pullout. The initial stiffness, peak load, and the residual frictional resistance of the steel fiber pullout are increased with the addition of the polypropylene fibers. The higher reinforcing efficiency of steel fibers in the presence of polypropylene fibers is due to improved fiber–matrix bond, which results in a higher cohesive stress at smaller crack openings.

中文翻译：

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钢和大聚丙烯混合纤维混合物混凝土断裂响应中的内聚应力和纤维拔出行为

评估了含有钢和大聚丙烯混合纤维混合物 (HyFRC) 的混凝土的断裂行为，并与钢纤维增强混凝土 (SFRC) 进行了比较。与 SFRC 具有相同体积分数的纤维混合物显示可改善断裂响应。在小裂纹分离处，开裂后，与 SFRC 相比，HyFRC 会立即产生更高的内聚应力。混凝土中的聚丙烯纤维在较大的裂缝分离处贡献内聚应力。混凝土基体中的聚丙烯纤维通过在拉拔开始时调动更高的阻力来提高钢纤维的效率。钢纤维拉拔的初始刚度、峰值载荷和残余摩擦阻力随着聚丙烯纤维的加入而增加。