Shear behavior of environmentally friendly rubberized RC beams externally strengthened with side-bonded prefabricated SHCC plates

This research proposes a sustainable solution for discarded tire disposal by repurposing rubber as a sand replacement in concrete mixtures for reinforced concrete (RC) beams. Furthermore, it examines the strengthening of rubberized beams using prefabricated strain-hardening cementitious composite (SHCC) plates to mitigate potential reductions in ultimate load or ductility caused by rubber incorporation in the concrete mixture. An experimental program was designed, consisting of 16 half-scale RC beams with shear deficiencies tested under three-point loading. The program investigates the effect of replacing sand with recycled rubber at proportions of 10 %, 30 %, and 50 %. Additionally, it examines the arrangement of the strengthening plates, either vertical or inclined at a 45° to the beam axis, as well as the fixation method, using either epoxy alone or a combination of epoxy and 10 mm steel anchors. The results indicate that vertical and inclined SHCC plates, fixed with epoxy alone, enhanced the ultimate load of rubberized beams containing 10 % rubber by 5 % and 16 %, respectively, compared to the reference beam cast entirely with sand. Furthermore, the beam cast with 10 % rubber and strengthened with inclined plates fixed using both epoxy and steel anchors exhibited the highest increase in ultimate load and ductility among the tested specimens, with improvements of 32 % and 85 %, respectively, relative to the reference beam. In addition to the experimental program, this study develops an analytical model to predict the ultimate load of rubberized beams strengthened with SHCC plates, considering the rubber content, the arrangement of the strengthening plates, and the fixation method.