A high-performance rubberised alkali-activated mortar for repair of RC beams

•A high-performance rubberised alkali-activated mortar is designed.•Many small-scale and large-scale tests are conducted.•The mortar contains small embodied carbon and has low water absorption capacity.•It exhibits improved ductility as well as compressive and bonding strength.•It shows superior compatibility with concrete compared to the existing mortars. The application of recycled waste tyre rubber in construction materials is increasingly growing due to its economic, environmental, and technical benefits. This study, in particular, examines the potential use of a waste tire rubber alkali-activated mortar in effective repair of damaged RC beams, which contains a very slight embodied-carbon footprint compared to the existing repair mortars. To assess the effectiveness of the proposed mortar for repair purposes, an extensive set of small-scale mortar samples with diverse contents are designed, assembled, and tested for compressive strength, flexural strength, bonding strength, and water absorption capacity. After discovering the efficient mortar mix that in general provides improved performance, large-scale RC beams are designed, constructed, damaged, repaired, and tested in flexure. It is found that the proposed mortar showed remarkable results and potential as a repair material. It contains significantly lower embodied carbon (35.3 kg/m3) compared to ordinary mortar (530.8 kg/m3). Also, the beam repaired by the proposed mortar exhibits high overall performance including strength capacity, ductility index, and bonding feature that are superior to the existing mortars. In particular, the experimental results demonstrated about 20 % increase in cracking load and 30 % increase in maximum displacement compared to the undamaged beam.