Reinforced concrete has been established as a major construction material since the last century. Some existing structures that no longer meet current standards and or even become functionally obsolete require immediate repair and strengthening. Strain-hardening cementitious composite (SHCC) was a class of high performance materials developed under the guidance of micromechanics theory. Its superior properties include high ductility and energy absorption with multiple cracking behaviour and high durability through tight crack control. With proper mix design, high tensile strength can also be achieved. In the literature, SHCC have been considered as a potential material for strengthening of reinforced concrete (RC) structures due to their compatibility in both physical and mecha...[ Read more ]

Reinforced concrete has been established as a major construction material since the last century. Some existing structures that no longer meet current standards and or even become functionally obsolete require immediate repair and strengthening. Strain-hardening cementitious composite (SHCC) was a class of high performance materials developed under the guidance of micromechanics theory. Its superior properties include high ductility and energy absorption with multiple cracking behaviour and high durability through tight crack control. With proper mix design, high tensile strength can also be achieved. In the literature, SHCC have been considered as a potential material for strengthening of reinforced concrete (RC) structures due to their compatibility in both physical and mechanical properties. This study focuses on the shear strengthening of beams with high strength SHCC. Direct shear test was performed to show that the bond strength between RC and SHCC under shear load was satisfactory, even without any anchoring system. Reinforced concrete beams designed with different shear span-to-depth ratio (1.5:1 and 2.5:1) were then cast. Thin layers of high strength SHCC were patched on both sides of the RC beams as a strengthening system. The results showed that the shear capacity of certain strengthened groups significantly increased compared to the reference group. Upon ultimate failure, the stable propagation of multiple cracking on the strengthening layer restrained surface concrete from spalling. In terms of repairing damaged RC beams, it was found that SHCC patches can effectively recover capacity loss. However, the level of recovery depends on the damage conditions. A finite element model was constructed to simulate the experimental tests, and satisfactory agreement between numerical and test results was achieved. A simple design equation for SHCC patching strengthening system was proposed according to the numerical parametric study using ABAQUS. This study demonstrated the feasibility of using high strength SHCC in shear strengthening and repair of RC beams. It also presented a simple design method for the strengthening system to lay the foundation for its practical use.