Characterization and Optimization of Mechanical and Impact Properties of Steel Fiber Reinforced Recycled Concrete

This study presents an experimental investigation to assess the feasibility of using concrete wastes in concrete production. To this end, natural aggregates were replaced by recycled concrete aggregates (RCA) with amounts of 0, 25, 50, 75, and 100% by volume. Moreover, recycled concrete were reinforced with 0, 0.5, and 1% by volume of hooked-end steel fibers. Workability, ultrasonic pulse velocity, water absorption, mechanical properties (compressive, splitting tensile, and flexural strengths) as well as impact resistance of 15 mixtures were investigated. This study also includes cost analysis. The results of investigations indicated that the use of 100% RCA has reduced the workability, compressive strength, splitting tensile strength, flexural strength, and impact resistance as much as 19, 20.1, 4.6, 11.5, and 20.2%, respectively. On the other hand, addition of steel fibers was able to offset the negative effects of RCA on the mechanical and impact properties. The results of the cost analysis also showed that the use of 100% RCA and 1% steel fibers increased the costs of concrete production by 62 and 76%, respectively. Finally, the results of multi-criteria optimization revealed that the use of RCA up to 50% is justified, in terms of workability, quality, water absorption, mechanical properties, impact resistance, and economic aspects.