Development of Carbon Fiber Reinforced Self-Consolidating Concrete Patch for Repair Applications
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Fiber-reinforced self-consolidating concrete is a relatively new material in civil engineering applications. The purpose of this study is to examine the effects of discrete Pitch-based carbon fibers on the fresh properties of self-consolidating concrete (SCC). Ten different carbon fiber-reinforced self-consolidating concrete (CFRSCC) mixtures were produced with two water/binder (W/B) ratios of 0.35 and 0.4, and 0%, 0.25%, 0.5%, 0.75%, 1% carbon fibers by concrete volume. Silica fume was used in all concrete mixtures to improve the dispersion of carbon fibers and the cohesiveness of the SCC. In addition, a high-range water reducer (HRWR) was used to enhance the workability of the concrete. The flow characteristics of the concrete mixtures were determined with respect to slump flow, J-ring slump, and T50 slump flow time. The segregation resistance of the concrete mixtures was evaluated by using the sieve stability test. Visual stability index (VSI) was also used to assess the segregation resistance of concrete. Hardened properties such as compressive strength, splitting tensile strength, and fracture energy were evaluated. Test results revealed that the increased amount of carbon fibers decreased the flowing ability (filling ability and passing ability). Therefore, a greater HRWR dosage was required to achieve the targeted flow properties. The hardened test results showed that increasing the carbon fiber content decreased the compressive strength of the SCC, while the splitting tensile strength of the SCC was increased. Based on the fresh and hardened properties, two different mixes were chosen as optimum mixes in respect to the fresh and hardened properties as well as the cost of producing CFRSCC mixtures. These two mixes were mix M1 (SCC, 0% fibers) and mix M3 (CFRSCC, 0.50% fibers). Eleven RC beams were tested to investigate three different repair configurations: flexural-top patch, flexural bottom patch and shear span patch. Three different repair patch materials were used (Sikacrete-08 SCC, M1 SCC, and M3 CFRSCC). The structural load results showed that the patch repair was most effective (increasing ultimate load and ductility) as a flexural-top patch and shear-span patch. Using a CFRSCC patch changed the mode of failure from shear to flexural failure in the shear-span patched beams.