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Ultra-High-Performance Strain-Hardening Cementitious Composites (UHP-SHCC) is one form of fiber reinforced composites, which has high compressive and tensile strengths along with high strain capacity in tension with strain hardening plateau. Obviously, proper selection of strengthening/retrofitting material plays an important role in restoring the lost capacity of the strengthened/retrofitted member. This paper investigated experimentally the effect of internal reinforcement in the UHP-SHCC specimens on the tensile strength as well as the cracking characteristics. Seven UHP-SHCC specimens with identical dimensions of 500 x 150 x 50 mm were tested under pure axial tension. Different configurations of the internal reinforcement were considered; namely, internal orthogonal mesh of clear spacing of 50 mm in both directions, or smooth bars of 6 mm diameter. For both configurations, different reinforcement ratios were considered. The experiential results showed that the internal mesh configuration enabled the specimen to develop better crack distribution along with higher tensile capacity compared to those of specimens having internal smooth bars configurations. In addition, increasing the internal reinforcement ratio resulted in increase the tensile strength of the UHP-SHCC as well as reduce the average crack spacing.

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This paper presents the experimental findings for different strengthening techniques applied on defected reinforced-concrete cantilever slabs to restore lost flexural capacities owing to insufficient bond length of the main tensile steel. The restoration technique was based on compensation of the main tensile steel by near-surface mounted steel bars, externally bonded steel plates or externally bonded carbon fibre-reinforced polymer sheets. In addition, new hybrid techniques are presented, which merge the traditional techniques with a 20 mm thick ultra-high-performance strain-hardening cementitious composites (UHP-SHCC) layer. It was found that the strengthening technique based on the embedded steel bars on the UHP-SHCC overlay enabled the strengthened slab to restore its lost capacity and outperformed it by about 5% compared to that of the properly detailed slab. Nevertheless, this restoration was at the expense of the exhibited ductility. Conversely, the strengthening technique based on the application of externally bonded steel plates on a transition layer of the UHP-SHCC material enabled the strengthened slab to restore the lost capacity by about 96% as well as to outperform its ductility by more than 29% compared to those of the properly detailed slab.

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