The Combined Effect of Carbon Fibers and Different Waste Aggregates on the Strength and Modulus of Elasticity of Modified Metakaolin-Based Geopolymer Concrete

Abstract Researchers are increasingly exploring non-crystalline alkali-aluminosilicate geopolymers to utilize byproduct waste from geopolymer concrete (GPC) and reduce carbon dioxide emissions. However, the material's quasi-brittle nature limits its application. Recent studies on incorporating various fibers aim to improve this limitation. This research reviews the mechanical properties of modified metakaolin fiber-reinforced geopolymer concrete, including the use of waste aggregate. At a 5% by weight ratio, calcium oxide and silica fume were added to metakaolin (MK). MK, coarse aggregate, fine aggregate, superplasticizer, and additional water were reacted with a mixture of sodium hydroxide and sodium silicate solution at 372, 910, 603, 8, 56, 83, and 192 kg/m 3 , respectively. This research investigates an eco-friendly approach by partially replacing 10% of the natural coarse aggregate in geopolymer concrete with recycled plastic waste or tire crumb rubber. It also examines the mechanical properties of fiber-reinforced geopolymer concrete with 0, 0.15, and 0.2% carbon fiber additions. The study evaluates the impact of these carbon fibers on the mechanical properties, including compressive strength, tensile strength, and modulus of elasticity, particularly in the context of utilizing recycled aggregates. The study found that incorporating fibers, particularly carbon fibers, significantly improved the properties of GPC mixes. The addition of 0.2% carbon fiber resulted in notable increases in tensile characteristics, modulus of elasticity, and compressive strength. Crumbed rubber showed a 10% improvement, while splitting tensile strength and static modulus of elasticity increased by 59% and 25%, respectively. Microstructural analysis of the mixtures with and without carbon fiber supported these findings.