Effect of Synergistic Incorporation of Fiber Reinforced Polymers and Rice Husk Ash on Behavior of Recycled Concrete

Abstract

The adoption of sustainability in buildings is increasingly important as natural concrete aggregate supplies diminish. The disposal and remediation of construction and demolition (C&D) waste are costly and environmentally harmful. Recycling C&D waste offers a more sustainable option, potentially reducing natural aggregate usage and benefiting the environment. However, recycled concrete often has substandard hardening properties compared to natural concrete aggregate (NCA). The weakest bond in recycled concrete typically occurs between the recycled concrete aggregate (RCA) and other components, including low-density mortar. To address these shortcomings, enhancing recycled aggregate (RA) with appropriate treatment methods is essential. Reinforcing recycled concrete (RC) with steel fibers, polypropylene fibers, and polyester polymers has shown promise in improving its mechanical performance. These materials contribute to higher tensile strength, improved stiffness, and better tensile strain capacity, all of which are crucial for recycled concrete's durability. An experimental study was conducted to evaluate the combined effects of rice husk ash (RHA), steel fibers, polypropylene fibers, and polyester polymers on the hardening properties of RC. The study focused on key mechanical properties, including compressive strength (CS), splitting tensile strength (STS), and flexural strength (FS). A slump test assessed the workability of fresh concrete, while water absorption (WA) tests examined the permeability resistance of RC compared to NCA. Using the ACI Method of Mix Design 211-1-91, the concrete mix included 10%, 12.5%, and 15% RHA as cement
Replacement, along with 0.75%, 1%, and 1.25% steel fibers. Additionally, 0.80%, 1%, and 1.20% polypropylene fibers with polyester polymer were used as supplementary materials with 100% RCA. The study found that replacing 10% cement with RHA and adding 0.75% steel fibers or 0.80% polypropylene fibers with polyester polymer enhanced the hardened properties of RCA. However, exceeding these replacement levels led to reduced strength and durability, highlighting the need for optimized material proportions to balance sustainability and structural performance.
Keywords: Construction & Demoliti