Study on the strength properties of coir fiber reinforced concrete containing waste brick powder dust as sand replacement

The increasing production of construction and demolition waste has increased the necessity of sustainable concrete formulations. The current study assesses the viability of using waste brick powder (WBP) as a partial substitution of fine aggregate at a percentage of 0% to 40% and coir fiber (CF) at a volume of 0.5 to 2% in M20 grade concrete. Fresh mix properties were determined in terms of slump, Vee-Bee and compaction-factor tests whereas mechanical properties such as compressive, flexural strength and split tensile were measured at 7 and 28 days. The tests on durability were done by exposing the specimens to 5% of HCl and H₂SO₄ for 60 days. The optimal mechanical performance was developed for a mix combination of 10% WBP and 1% CF achieving the compressive strength of 26.04 MPa which exceeded the required characteristic strength for M20 mix while maintaining the acceptable workability. Notable improvements in case of flexural and split tensile strength was also observed reflecting enhanced crack-bridging capacity and matrix integrity rather than disproportionate gains in compressive strength. Though higher WBP and fiber contents reduced the workability and the strength marginally, all the mixes remained withing the range of the conventional mix. The optimum blend also exhibited lower strength and mass loss under acidic exposure compared to the control mix, indicating improved resistance to aggressive environments. Thus the findings demonstrate that moderate use of WBP and Coir fiber can produce a structurally viable M20 grade concrete with improved strength and durability performance offering a sustainable alternative to conventional fine aggregate usage.