Mechanical properties and shear strength of rubberized fibrous reinforced concrete beams without stirrups

Abstract

• Presenting the experimental shear strength results of sixteen rubberized RC beams with/without fibers. • Investigating the impact of crumb rubber on mechanical properties and shear strength of concrete beams. • Investigating the effect of fiber types and ratios on the shear strength of rubberized reinforced concrete beams. • Investigating the effect of shear span to depth ratio on the shear strength of rubberized RC beams with/without fibers. This study investigates the mechanical properties and shear strength of rubberized reinforced concrete (RC) beams with/without fibers with no web reinforcement. A total of 16 RC beams were cast and tested under four points bending to fail in shear. The study parameters are; replacement ratio by volume of fine aggregate by crumb rubber (CR) (0, 15, 30, and 40%), types of fibers (hooked long steel fiber, smooth short steel fiber, and polypropylene fiber), fiber volume fraction (0, 0.4, and 0.8%) and shear span to depth ratio a/d (2.5, 3.5, and 4.5). The results show that the mechanical properties of rubberized concrete and its weight are reduced with increasing the CR content due to the low strength, stiffness, and elastic modulus of CR, while the addition of different types of fibers, particularly hooked large steel fiber, significantly improves the mechanical properties of rubberized concrete. Using lightweight CR contributes to increasing the deformability of the tested beams and reducing their self-weight. However, increasing the CR content decreased their ultimate shear force, post-diagonal crack shear resistance, and energy absorption capacity. The inclusion of CR and fibers in concrete production can be considered as a potential technique to develop new types of eco-friendly concrete with decreased self-weight and exhibits higher shear strength than that of the control beam. Moreover, the comparison of experimental results with the predicted results of five codes and six equations from the literature showed that most of them overestimate the shear capacity of rubberized RC beams; therefore, a new predicted equation is required to predict the combined effect of rubberized fibrous RC beams.