Authors: K. Sathish Kumar, Assistant Professor A. Ram Kumar
Abstract: This research investigates the development and structural performance of fly ash-based Geopolymer Concrete (GPC) reinforced with polypropylene fibers as a sustainable alternative to conventional Ordinary Portland Cement (OPC) concrete. The study addresses the growing environmental concerns associated with cement production, particularly the high emission of carbon dioxide and the disposal of industrial waste materials. By utilizing Class F fly ash as the primary alumina-silicate and activating it with sodium hydroxide and sodium silicate solutions, a cement-free geopolymer binder was produced to promote environmentally friendly construction practices. The experimental program focused on evaluating the influence of polypropylene fibers on the mechanical and micro structural properties of geopolymer concrete. Geopolymer mixtures were prepared using locally available fly ash, fine and coarse aggregates, and alkaline activators with different molar concentrations. Heat curing was adopted to accelerate the geopolymerization process and to achieve rapid strength development. The study examined important engineering properties including compressive strength, split tensile strength, flexural strength, modulus of elasticity, ultrasonic pulse velocity, and durability characteristics to assess the suitability of GPC for structural applications. In addition to mechanical evaluation, the research investigated the nano- and micro structural behaviour of polypropylene fibre-reinforced geopolymer concrete through characterization of pore volume, crystalline structure, morphology, surface area, and surface-active phases. These analyses provided insight into the formation of a dense alumina-silicate gel matrix and the role of fibers in controlling micro-crack propagation and improving the internal structure of the composite. The interaction between geopolymer binder and polypropylene fibers was found to enhance the integrity of the matrix while reducing brittleness. The results demonstrate that the incorporation of polypropylene fibers significantly improves tensile and flexural performance, crack resistance, and overall durability without compromising the environmental advantages of geopolymer concrete. Heat-cured fly ash geopolymer concrete exhibited excellent early-age strength, superior resistance to aggressive environments, and the potential to replace OPC concrete in sustainable infrastructure. The study concludes that polypropylene fibre-reinforced geopolymer concrete is a high-performance, eco-friendly construction material capable of contributing to low-carbon and durable structural development.
