Fresh and Mechanical Characteristics of Alkali Activated Fly Ash Slag Concrete Activated with Neutral Grade Liquid Glass

Abstract

Abstract: The development and use of geopolymer concrete continues to evolve as researchers and engineers refine mix designs, develop standardized guidelines, and explore new applications. One of the key benefits of geopolymer concrete is its lower carbon footprint compared to traditional Portland cement concrete. This reduction in carbon emissions is due to the elimination of clinker production, which is energy intensive and emits significant amounts of carbon dioxide. This sustainable alternative to Portland cement concrete plays an important role in reducing the environmental impact of the construction industry. Many prior studies on fly ash-slag based geopolymers have primarily focused on the characteristics of concrete that has undergone heat curing. This approach is seen as a constraint when it comes to in-situ casting applications in ambient conditions. Ambient curing of geopolymer concrete is a more energy-efficient and environmentally friendly option compared to heat curing, as it doesn't require the use of specialized curing chambers or high temperatures. However, it may require longer curing times to achieve the desired strength and making it important to plan the construction schedule accordingly. An experimental study was carried out using neutral grade liquid glass with a silica modulus (SiO2/Na2O) of 2.92 coupled with combinations of fly ash and Ground Granulated Blast Furnace Slag (GGBS) in proportions of 30:70, 50:50. The primary aim is to explore how altering the ratios of fly ash and GGBS impacts the mechanical characteristics of the resultant concrete for different solution/ binder ratios (0.6, 0.65 and 0.7) with a fixed binder quantity of 400 and 500 Kg/m3 under ambient curing conditions. The experimental program employed the fractional factorial method of experimentation to minimize the number of mix variations. In general, the findings indicated that higher levels of neutral-grade sodium silicate led to improvements in all mechanical properties. Conversely, an increase in the alkaline solution-to- binder ratio and curing temperature had a detrimental impact on the alkaliactivated slag concrete. Optimal results for hardening of concrete for demolding were obtained after two days of casting. The implications of this research could lead to the development of more sustainable and environmentally friendly alternatives in the field of construction materials.