Enhancing the Performance of Recycled Aggregate Concrete Using Micro-Carbon Fiber and Secondary Binding Material

In this study, the effect of micro-carbon fiber on the properties of concrete incorporating recycled coarse aggregate at three different levels, i.e., 0%, 50%, and 100% by volume replacement of natural coarse aggregate, was studied. Carbon fiber was incorporated at a dosage of 0.5% by volume fraction. The effect of silica fume or micro-silica on the efficacy of fiber reinforcement was also investigated. Studied parameters include important mechanical properties, such as compressive strength, splitting tensile strength, and flexural strength, and physical/quality parameters such as water absorption capacity and ultrasonic pulse velocity. The results showed that the mechanical and durability performance deteriorates with the increasing percentage of recycled coarse aggregate. Carbon fiber can significantly improve the tensile properties of recycled aggregate concrete. The combination of carbon fiber and silica fume proved to be highly useful in addressing both mechanical and durability concerns simultaneously. Concrete made with 50% recycled coarse aggregate, 8% silica fume, and 0.5% carbon fiber yielded 20% greater tensile and flexural strength compared to the control mix. Likewise, concrete containing 100% recycled coarse aggregate with silica fume and carbon fiber yielded higher tensile strength compared to the control mix. Silica fume ameliorated the bonding between fibers and matrix and improved the overall efficacy of fiber reinforcement.