In this study, aramid fiber (Kevlar^® 29 fiber) and carbon fiber were added into concrete in a hybrid manner to enhance the static and impact mechanical properties. The coupling agent presence on the surface of carbon fibers was spotted in Scanning Electron Microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS) graphs. The carbon fiber with a coupling agent affected the mechanical strength of the reinforced concrete. At 1% fiber/cement weight percentage, the hybrid fiber-reinforced concrete (HFRC) prepared using Kevlar fiber and carbon fiber of 12 and 24 mm in length under different mix proportions was investigated to determine the maximum mechanical strengths. From the test results, the mechanical strength of the HFRC attained better performance than that of the concrete with only Kevlar or carbon fibers. Foremost, the mix proportion of Kevlar/carbon fiber (50–50%) significantly improved the compressive, flexural, and splitting tensile strengths. Under different impact energies, the impact resistance of the HFRC specimen was much higher than that of the benchmark specimen, and the damage of the HFRC specimens was examined with an optical microscope to identify slippage or rupture failure of the fiber in concrete.

Fiber-reinforced concrete (FRC) has been used for over a century to improve the mechanical properties of concrete. Kevlar ^® 29 fiber (KF) is one of the most popular aramid fibers used in industrial products. This research investigated the effect of the fiber length, the weight ratio of fiber to cement, the mix-proportion of two fiber lengths, and the sizing on the fiber surface on the mechanical properties of Kevlar fiber-reinforced concrete (KFRC) under static, dynamic, and shock wave loadings. Two lengths of chopped KF and three different weight ratios of fiber to cement were mixed in the KFRC specimens for comparison. Moreover, this study also compared how the five mix-proportions of two fiber lengths affected the mechanical properties of mix-proportion KFRC. KF was dispersed by the pneumatic method first, and then, the separated KF was mixed into the concrete to make KFRC. The results indicated that the KFRC specimens with a 10‰ weight ratio of fiber to cement exhibited the maximum compressive, flexural, and splitting tensile strengths, regardless of whether the fiber length was 12 mm or 24 mm. The main finding showed that the specimen mixed with 24 mm KF could endure the highest impact resistance under different impact energies. From the shock wave test, the external damage on the front and rear faces of all KFRC slabs and the KFRC slab reinforced with two layers of KF sheets was less than that of the benchmark slab. The testing results showed that KF greatly enhanced the static and dynamic mechanical performances of concrete, and the KFRC specimen with a 10‰ weight ratio and 24 mm length KF with sizing exhibited the best performance.