Green Concrete Roads with Geo-Polymer Concrete: A Review

Concrete is the most widely used man-made material for construction across the globe. As a composite material, it binds inert aggregates such as sand and gravel with cement to produce strong, economical, and versatile building material. In India, cement production has already reached 450 million metric tons and is projected to grow at a rate of 8–9% annually. With the rapid expansion of infrastructure, more than 40% of this cement is consumed in concrete pavement construction. However, the production of ordinary Portland cement (OPC) releases nearly an equivalent mass of carbon dioxide into the atmosphere, contributing significantly to greenhouse gas emissions. Simultaneously, the country’s dependence on coal and lignite for thermal power generation results in the generation of large quantities of fly ash, as Indian coal typically contains 24–63% as compared to 3–20% in imported coal. Currently, fly ash production in India has reached 147 million metric tons per year, creating enormous challenges for disposal, land management, and air and water pollution. These pressing environmental concerns underscore the urgent need for sustainable alternatives to OPC-based concrete. Geopolymer concrete has emerged as one such promising solution. By utilizing fly ash, which is rich in silica and alumina, and activating it with alkaline chemicals, geopolymer concrete forms an aluminon-silicate gel that serves as the binding phase, eliminating the need for OPC or large amounts of water. This approach not only converts industrial waste into a valuable construction material but also produces concrete with strength comparable to conventional concrete. The present study reviews the potential of geopolymer concrete as both an alternative to OPC-based concrete and as a feasible option for large-scale applications such as pavement-quality concrete.