DEVELOPMENT OF SUSTAINABLE ECO-CONCRETE WITH KENAF FIBRE AND COATED RECYCLED CONCRETE AGGREGATE

Abstract

The urgent global demand for sustainable infrastructure has driven innovations in eco-efficient construction materials. This study explores the development of high-performance, sustainable concrete by integrating pozzolanic-treated recycled concrete aggregates (RCA) and kenaf fibre as eco-friendly alternatives to natural coarse aggregates and synthetic reinforcements. The research addresses the inherent limitations of RCA—such as high porosity, residual mortar, and weak interfacial zones—through a surface modification technique involving a blended calcined clay-cement slurry. Simultaneously, kenaf fibre is incorporated to enhance the tensile and flexural properties of the concrete matrix. Concrete mixes were produced with varying RCA replacement levels (30%, 45%, 60%, and 90%) using both untreated and pozzolanic-treated RCA. Comprehensive characterisation, including X-ray fluorescence (XRF), X-ray diffraction (XRD), and scanning electron microscopy (SEM), was employed to assess material and microstructural properties. Mechanical performance was evaluated through compressive, tensile, and flexural strength tests, alongside water absorption and density tests for durability analysis. Statistical optimisation using Response Surface Methodology (RSM) and ANOVA determined the influence of treatment and fibre incorporation on concrete performance. The results indicate that pozzolanic treatment significantly improved RCA concrete properties, with optimal performance observed at 45–60% RCA replacement. Treated mixes achieved a 28-day compressive strength of 36 MPa, a 5.3 MPa split tensile strength, and reduced water absorption to 3%, reflecting improved durability and structural integrity. These enhancements demonstrate the synergy between calcined clay treatment and natural fibre reinforcement. This study substantiates the viability of producing eco-concrete with treated RCA and kenaf fibre, promoting circularity, reducing carbon footprint, and contributing to sustainable development goals. It provides a framework for future applications in structural concrete, aligning with low-carbon construction practices.