Study on the Load-Bearing Characteristics of Fiber-Reinforced Concrete Members Using Low-Melting-Point Metal Fibers

Fiber-reinforced concrete, designed to complement the weakness of concrete by incorporating fibers, faces challenges during disposal, making material separation and recycling difficult and hindering progress toward a circular society. In an effort to overcome these challenges, an attempt was made to develop fiber-reinforced concrete utilizing the properties of metals that melt at low temperatures, such as aluminum. The approach involved subjecting only the metal fiber portion to heating considerably below the melting point of steel, facilitating the melting of metal fibers and separation from the concrete. To ensure the bond between fibers and concrete while preventing entanglement of low-rigidity, low-melting-point metal fibers, test specimens were created by combining different types and shapes of low-melting-point metal fibers. Materials and shapes that aligned with the objectives were identified based on the results of these material tests. Significantly, it was found that in cases of fiber reinforcement using low-melting-point metals, the advantageous approach lies in leveraging the energy absorption capacity derived from the deformability of low-rigidity fibers, rather than aiming to suppress crack openings to enhance structural performance. When small test specimens (100mm x 100m x 400mm or smaller) reinforced with aluminum fibers, one of the low-melting-point metals, were created, a challenge was encountered where aluminum reacted with cement, resulting in the formation of a weak layer at the fiber interface and a decrease in bond. To overcome this challenge, a pre-treatment was applied to form an oxide film on the surface of aluminum. This pre-treatment effectively suppressed the reaction at the interface and improved the bond. Finally, using these pre-treated aluminum fibers, reinforced concrete beams (RC beams) were created and loading tests were conducted, revealing a significant improvement in energy absorption compared to loading tests using ordinary concrete, achieving the expected outcomes.