Investigation of mechanical behavior of carbon fiber reinforced concrete under impact loads

In this study, the strength and energy absorption properties of carbon fiber-reinforced concrete under impact loads were investigated. In preparation for the dynamic tests, 152 mm diameter disc specimens were produced using the sample preparation and impact test setups in the ACI.544.2R guideline. The specimens were then subjected to low-velocity impact loads under an instrumented drop-weight test setup. Quasi-static compression and splitting tests were also conducted on the prepared cube specimens to observe the effects of the fibers on the characteristics of the concrete. Carbon fibers of two different lengths, 3 mm and 12 mm, were used. Three different fiber ratios were used, depending on the concrete volume: 5 kg/m3, 10 kg/m3, and 15 kg/m3. The groups with the best compressive and splitting strength values in the study were those using 3 mm fibers at 5 kg/m3 and 12 mm fibers at 10 kg/m3. Compared to the control samples, the strength increases were approximately 23% and 28%, respectively. In the group where 3 mm fibers were used at a rate of 10 kg/m3, the fiber reinforced concretes maintained their strength, while decreases were observed in all other samples comparing the control group. The most prominent group in terms of impact performance differed from those in the static tests; samples using 3 mm fibers at a rate of 15 kg/m3 exhibited the best performance, and this rate was determined to be the optimum rate for the study. Although the maximum force that both groups, which performed best in the static condition, could receive maximum impact force 7% lower than the control samples, they increased their energy consumption by approximately 35% compared to the control concretes. It was observed that the amount of damage in the concrete remained limited due to the carbon fiber addition. In general, 3 mm fibers performed better than 12 mm fibers in terms of both static and dynamic effects. Key Word: Carbon Fiber Reinforced Concrete; Compressive Strength; Dynamic Impact Behavior; Instrumented Drop-Weight Test