A Study on the Mechanical Properties of the Hybrid Fiber-Reinforced Mortar Using the Macro Steel and Micro Carbon Fibers

In the present study, an experiment was conducted to investigate the mechanical properties such as fluidity, compressive strength and flexural performance (flexural strength and toughness) of a single fiber-reinforced mortar (FRM) using only macro steel fiber (SF) or micro carbon fiber (CF) with different material properties and SF-CF hybrid FRM using a mixture of macro SF and micro CF. The specimens incorporated macro SF and micro CF in the mix proportions of 100-0%, 75-25%, 50-50%, 25-75% and 0-100% by volume at a total fiber volume fraction of 1.0%. Their mechanical properties were further compared and reviewed with the plain mortar at 28 days of age. The experimental results of fresh mortar showed that the table flow of mortar using only macro SF was slightly reduced compared to plain mortar, whereas the table flow of mortar using only micro CF and SF-CF hybrid mortar decreased significantly with increase of micro CF. It was revealed from the test of the hardened mortar that the SF-CF=75-25% (M3) specimen showed the highest compressive and flexural strength, and the SF-CF=50-50% (M6) specimen obtained the highest flexural toughness. Therefore, it was possible to confirm the synergistic reinforcement effect of that enhanced the strength and improved the flexural performance by hybrid of macro SF and micro CF. Based on the results of this experiment, the optimal mix proportion of SF-CF hybrid FRM is proposed in this paper to improve the compressive strength, flexural strength and flexural toughness.