Behavior of RC beams strengthened with strain hardening cementitious composites (SHCC) subjected to monotonic and repeated loads

Ultra High Performance Strain Hardening Cementitious Composites (UHP-SHCC) is a newly developed construction material, has large advantages on large strain capacity as well as high compressive and tensile strength, which is useful for strengthening or repair concrete members. However, some important obstacles need to be studied, such as the strain localization occurs in the UHP-SHCC strengthening layer around the substrate concrete cracks, which severely limits the ductility of the strengthened beam subjected to monotonic and repeated loads. In the present study, ten specimens were tested experimentally, which divided into two major groups, each group contains five specimens, one as a control and four strengthened with constant UHP-SHCC layer thickness having variable reinforcement ratios embedded in the middle of the strengthening layer. Two types of loading were applied; Monotonic loading for the first group and short time repeated loading for the second group. The recorded tests showed that use additional reinforcement embedded in the strengthening layer for beams strengthened with UHP-SHCC become sufficient at certain limit to eliminate the observed early strain localization and to gain adequate ductility under both monotonic and repeated loading. Another important conclusion is the strengthening of RC structures using an unreinforced UHP-SHCC layer may lead to a brittle failure especially in case of repeated loading.