Evaluation of mechanical properties of fiber reinforced recycled concrete: effect of size and amount of recycled aggregate, type and amount of fibers

Abstract

In this research, recycled concrete aggregates are used instead of natural aggregates in concrete and then the recycled concrete is reinforced by fibers. The aim of this study is to investigate the effect of size and also the amount of the recycled concrete aggregates on the mechanical properties of concrete and then investigating the effect of addition of polypropylene and steel fibers on improving the mechanical properties of concrete. The results showed that compressive strength of concrete decreased by increasing replacement ratio of recycled aggregates. Also, the replacement of fine aggregate at the level of 30 percent has not significant effect on the compressive strength of concrete and so this mix can be selected as the optimum recycled mix design. In addition, the use of the fiber improves considerably the tensile and flexural strength of the recycled concrete so that the steel fiber has more positive effects on the tensile and flexural strength in comparison to the polypropylene fiber. In addition, when the concrete reinforced by the fiber is broken, the concrete is not disrupted and the fiber has an important role to reduce the growth of cracks after break. In this research, recycled concrete aggregates are used instead of natural aggregates in concrete and then the recycled concrete is reinforced by fibers. The aim of this study is to investigate the effect of size and also the amount of the recycled concrete aggregates on the mechanical properties of concrete and then investigating the effect of addition of polypropylene and steel fibers on improving the mechanical properties of concrete. The results showed that compressive strength of concrete decreased by increasing replacement ratio of recycled aggregates.Also, the replacement of fine aggregate at the level of 30 percent has not significant effect on the compressive strength of concrete and so this mix design can be selected as the optimum recycled mix design. In addition, the use of the fibers improve considerably the tensile and flexural strength of the recycled concrete so that the steel fiber has more positive effects on the tensile and flexural strength in comparison to the polypropylene fiber. Also, when the concrete reinforced by the fiber is broken, the concrete is not disrupted and the fiber has an important role to reduce the growth of cracks after break.

Keywords

• recycled concrete
• recycled aggregate
• mechanical properties
• steel fiber
• polypropylene fiber