Shear behavior of reinforced concrete beams using treated recycled concrete aggregate

The shear behavior of ten full scale reinforced concrete beams that were constructed from natural aggregate, recycled aggregate and treated recycled aggregate was experimentally and analytically studied. All beams were constructed without stirrups and with 50% and 100% recycled aggregate. The beams were tested for a shear span-to-depth ratio (a/d) equal to 2.0 and 3.0. The performance of recycled aggregate was improved through enhancement treatment methods. The recycled aggregate was pre-soaked in hydrochloric acid (HCl) for 24 h to remove adhered mortars attached to original recycled aggregates, and then they were impregnated with sodium metasilicate pentahydrate solution for one hour to coat their surfaces. The behavior of the shear-critical beams was studied through reporting the load-deflection curves, ultimate load values, and crack propagation during static tests. The experimental shear capacities of the beams were compared with theoretical values from different international codes and fracture mechanics approaches. The experimental results showed that in general using treated recycled aggregate improved slightly the shear capacity of the beams in comparison with natural and untreated recycled aggregate. Furthermore, the shear strength comparisons showed that the treated recycled aggregate beams were considered more conservative compared to the natural and untreated recycled aggregate beams regardless of the shear span-to-depth ratio.