Experimental Investigation on Ultra-Thin White Topping Using Fly Ash-Based Geopolymer Concrete

In the present scenario of rapid urbanization and increasing traffic load, the performance of conventional flexible pavements is deteriorating at a faster rate due to rutting, cracking, and fatigue failure. Ultra-Thin White Topping (UTWT) has emerged as an effective rehabilitation technique in which a thin layer of concrete is placed over existing bituminous pavement. However, the use of Ordinary Portland Cement (OPC) leads to high carbon emissions and environmental concerns. This study focuses on the development and application of fly ash-based geopolymer concrete (GPC) as a sustainable alternative to conventional cement concrete for UTWT. Geopolymer concrete is produced by the reaction of fly ash (rich in silica and alumina) with alkaline activators such as sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃), eliminating the need for cement completely. Based on the referenced study , M40 grade geopolymer concrete was prepared with different molarities (10M, 12M, 14M). In this thesis, values are slightly modified and extended for better understanding. Various tests such as compressive strength, flexural strength, fatigue behavior, and workability were conducted. Results indicate that compressive strength increases with increase in molarity and geopolymer concrete shows excellent performance for pavement applications. The fatigue life also improves under cyclic loading conditions. Additionally, cost analysis shows around 10% reduction, and energy analysis indicates approximately 45% energy saving compared to OPC concrete. Thus, UTWT using fly ash-based geopolymer concrete is found to be an eco-friendly, durable, and economical solution for pavement rehabilitation.