Experimental investigation of eco-friendly fiber-reinforced concrete using recycled and natural fibers, integrated with recycled aggregates

This study investigates the integration of recycled and natural fibers with recycled concrete aggregates to develop environmentally friendly fiber-reinforced concrete (FRC), with a primary aim of maintaining or enhancing its properties. Four concrete mixtures, namely plain concrete (C-Plain), recycled steel fiber-reinforced concrete (C-RSF), recycled plastic fiber-reinforced concrete (C-RPF), and kenaf fiber-reinforced concrete (C-KF), were formulated and analyzed for their fresh, hardened, and durability characteristics. A 50% replacement of natural coarse aggregates' weight with recycled concrete aggregates (RCA) was implemented. By standardizing fiber volume fractions at 1.0% for all FRC mixtures, the study evaluated properties such as workability, dry density, ultrasonic pulse velocity (UPV), compressive strength, modulus of elasticity, post-cracking flexural performance, modulus of rupture, flexural toughness, splitting tensile strength, and freeze-thaw resistance after 100 and 300 cycles. Testing involved three specimens for each parameter at 7 and 28 days. The results indicated positive effects on post-cracking flexural performance, modulus of rupture, flexural toughness, splitting tensile strength, and durability with the incorporation of recycled and natural fibers. Notably, C-RSF demonstrated the highest compressive strength (46.63 MPa), flexural toughness (64.35 kN-mm), and modulus of rupture (7.46 MPa) compared to other FRC composites. Additionally, it exhibited minimal weight loss (2.18% and 3.07%) after freeze-thaw cycles, indicating exceptional durability. C-RSF exhibited superior performance, while C-KF showed enhancement slightly below that of C-RSF. Although not reaching the level of C-RSF, C-RPF positively influenced concrete performance. Compressive response either maintained performance or exhibited marginal reduction. The findings carry significant implications for developing environmentally conscious construction materials with enhanced mechanical and durability properties, thereby advancing sustainable construction practices.