Flexural Behavior of Recycled Aggregate Concrete Beam with Varying Dosage of Steel Fiber

Abstract

Natural resource scarcity and demolition waste suggest that recycled stone aggregates to be used instead of fresh aggregates as an alternatives. Recycled aggregate provides less strength to concrete than natural aggregate. Fiber such as steel fibers can be added to concrete at a low percentage volumetric addition to fill the strength gap. The purpose of this study is to investigate the flexural behaviors of recycled stone aggregate concrete using steel fiber with a length of 30 mm by volume fractions of 0.45%, 0.90%, 1.35%, and 1.80% of concrete. Coarse aggregates specially recycled stone was obtained from demolished concrete structures and laboratory waste. The desired concrete strength was 30 MPa and the water to cement ratio of 0.46 were chosen based on the mix design, and such concrete was expected to be used for structural beams. The slump test was carried out to ensure the workability of the designed concrete. Compressive strength of cubes was measured at 7 and 28 days. From mean compressive strength, deviation, coefficient of variance (COV), standard error, and lower and greater range of 95% confidence interval analysis, it is found that 1.35% of steel fiber can be used as optimal percentage along with 100% recycled aggregate. Finally, for large scale beams, a combination of recycled stone aggregate and an optimal percentage of steel fiber was used to evaluate flexural behaviors such as first cracking load, ultimate load, load-deflection behavior, and cracking pattern for future practical application. When compared to the reference specimen, the first cracking load and ultimate load bearing capacity of the beam strengthened with steel fiber increased by 11.60% and 14% compared to reference beam with 0% fiber content. Furthermore, the degrees of diagonal tension cracking in strengthened beams were less severe than reference beam. To summarize, optimal dosages of steel fiber with recycled stone can provide sufficient flexural performances of recycled stone aggregate concrete beams.