Experimental Study On Flexural Properties Of Steel Fiber Reinforced High-Strength Recycled Concrete Beams

This paper took fly ash, silica fume as cementing material to replace part of cement, took recycled coarse aggregate to replace part of gravel, and blended three types of steel fibers with different ways to configure steel fiber reinforced high-strength recycled concrete for studying mechanical properties. The flexural properties of 11 beams were studied by adding two kinds of reinforcement ratio in the same mix design. The results showed that:Partially recycled coarse aggregate was incorporated into high-strength concrete has little effect on strength and bearing capacity of beam. Fly ash and silica fume could refining and filling micro-cracks of recycled aggregate to improve the strength of recycled concrete and the flexural capacity of beam, and reduce the growth of deflection and crack width. When reinforcement was 2.31%, high-strength recycled concrete beam occurred less muscle damage with low bearing capacity. When reinforcement was 3.61%, beam occurred shear compression failure, brittle fracture. When reinforcement was 2.93%, it was balanced-reinforced beam, and occurred normal section failure.The difference of steel fiber’s end-structure could improve the compressive strength of high-strength recycled concrete and flexural capacity of beam in varying degrees. Type B of steel fiber played the best role in improving the bearing capacity,19.4% higher than C7R3F2, and 21.6% higher than Plain. In addition, steel fiber could improve the cracking load of beam, reduce the crack width and spacing, and reduce the growth of deflection by increasing tensile strength of concrete. Wherein, type A had the best effect on increasing the cracking load of beam, type B was more obvious in reducing crack width and the growth of deflection. Type C made in laboratory significantly reduced the elastic deformation’s amount of beam and played a good anchoring effect in the initial loading. And its role was more obvious in terms of reducing the number and spacing of cracks.For high-strength recycled concrete beams, the ultimate flexural strength of normal section, crack width and span deflection could be calculated in accordance with the relevant norms. However, for steel fiber reinforced high-strength recycled concrete beams, the influence coefficients of steel fiber’s end-structure need to be introduced into the formulas to calculate the ultimate flexural strength of normal section, crack width and span deflection.It was feasible that ANSYS software could be used to speculate the actual carrying capacity of engineering for high-strength recycled concrete beams. However, for steel fiber reinforced high-strength recycled concrete beams, the results of ANSYS analysis were consistent with the results of theoretical calculations, which were all less than the results of actual test.