Shear behavior of reinforced concrete beams comprising a combination of crumb rubber and rice husk ash

In this paper, experimental studies were conducted to examine the shear behavior of reinforced concrete beams, including a combination of crumb rubber (CR) and rice husk ash (RHA). One of the key objectives of the concrete industry is to reduce global emissions and provide environmentally friendly concrete. Twelve RC beams with four replacement levels of CR (0 %, 5 %, 10 %, and 20 %) by fine aggregate (FA) and three substitution ratios of RHA (0 %, 10 %, and 20 %) by cement (one beam from each mix) with dimensions of 120 x 250x2000 mm were cast and tested under four-point loading conditions. The experimental outcomes display that incorporating a combination of CR and RHA reduces workability. The introduction of RHA enhanced both the compressive and tensile strengths. Conversely, the inclusion of CR significantly impacted the loss in concrete strength. The shear capacity, stiffness, and toughness of the tested beams were noticeably enhanced with the addition of RHA up to 10 %, then dropped with the addition of 20 % RHA but remained higher than those of the reference beam. On the contrary, the introduction of CR had a negative effect on the shear capacity and stiffness of tested beams, and incorporating RHA up to 10 % enhanced these effects. To maintain environmental sustainability and preserve natural resources, the ideal substitution ratios for the concrete mix are 10 % CR and 10 % RHA, which produce an acceptable shear capacity with a slight drop of approximately 4.0 %. Additionally, a comparison was conducted between the predicted shear capacity of four design code equations (ACI 318-2019, ECP 203, BS8110, and Euro-2) and the experimental results obtained from all test beams.