Globally, since there are more systems of civil infrastructure, there are also more degraded buildings and structures. If upgrading or strengthening is a practical option, complete replacement is likely to be an escalating financial burden and may be a waste of natural resources. It is necessary to repair or strengthen a number of reinforced concrete buildings and structures in order to boost their load-bearing capabilities or improve their ductility under seismic stress. Additionally, due to changes in service circumstances, a structure might need to be modified to reduce deflections or manage cracking. Strengthening may be preferable to limiting usage, capping applied loads, and regularly inspecting the structure rather than removing the existing structure or part and building a new one. This study aims to examine the flexural, shear, and combined effect of flexural and shear behavior of reinforced concrete (RC) beams strengthened with externally bonded spent catalyst-based ferrocement laminates and compare them to the control beams (unstrengthened) under two-point loading conditions. This study involves researching laminates with various spent catalyst doses, such as 3, 6, 9, and 12%, in an effort to determine the best amounts that will improve the structural performance of ferrocement laminates. Twelve spent catalyst-based ferrocement laminates measuring 500(L) × 125(B) × 20 mm (thickness) with 3% volume fraction of meshes each were cast and tested in the lab as part of the preliminary investigation. For repeatability, three laminates per case were employed. Eight numbers of under-reinforced RC beams measuring 75(L) × 100(B) × 150(D) mm were cast for the main study; six numbers were strengthened with optimized spent catalyst-based ferrocement laminates bonded with flexible epoxy systems at the tension zone, shear zone, and combination of tension and shear zone.
Two of the beams were cast as control specimens. The beams were then evaluated using a Universal Testing Machine (UTM) with a 1000 kN capacity under two-point loading conditions. As a result, the strength, yield load, ultimate load, stiffness, ductility, and related failure modes of all tested beams’ flexural and shear performances were examined. According to a preliminary analysis of laminates made of spent catalyst, the dosage of 9% provides good flexural strength in comparison to other doses. In comparison to the strengthened beam, the control beam’s initial cracks appeared earlier. In comparison to the control beam, the strengthened beam has an increase in load-carrying capacity of 18% for flexure, 16% for shear, and 30% for the combined impact of flexure and shear. In comparison to the control beam, the deflection of the strengthened beam was decreased by close to 20 to 40% for flexure, 10 to 30% for shear, and 15 to 20% for the combined effects of flexure and shear at the same load level. In relation to control beams, the ductility also improved up to 30% for flexure, 25% for shear, and 25% for the combined impact of flexure and shear. Similar to this, the retrofitted beam is stiffer than the control beam by approximately 40% for flexure, 48% for shear, and 30% for the combined effect of flexure and shear. Theoretical formulation by section analysis is also derived and it gives close agreement with control and strengthened beams. The flexural and shear strengthening of the RC beam retrofitting system is effectively increased by using spent catalyst-based ferrocement laminates. No beam showed signs of premature and brittle failure. According to the test findings, it can be said that spent catalyst-based ferrocement reinforced beams perform better in every way than control beams.
KEYWORDS: Ferrocement Laminates; Flexural Retrofit; Shear Retrofit; Two-Point Loading; RC Beams