Influence of GGBS and Alkaline Ratio on Compression Strength of Geopolymer Concrete: Influence of GGBS and Alkaline Ratio on Compression Strength of Geopolymer Concrete

Abstract

The cement production process tends to be a major source of greenhouse gas emissions in construction projects all over the world that rely on cement for concrete purposes in massive amounts. According to [1], during the cement manufacturing process, the same amount of carbon emission is released into the atmosphere for one ton of cement. This is due to the decarbonization of limestone in kilns during cement production and the combustion of fossil fuels. [2] During cement production, it emits 0.53 tons of carbon dioxide, and if the cement is produced using carbon fuel, a total of 0.98 tons of carbon dioxide is released into the atmosphere, resulting in global warming and emissions. Thus, in the construction project, replacing cement with geopolymer material reduces pollution in two ways: reduction of CO₂ emissions into the air by lowering cement consumption; and usage of fly ash, which is a by-product of thermal power plants. Industries that produce cement are responsible for removing waste and repurposing it as a viable alternative to cement [3]. The processing of fly ash contributes 80 to 90% fewer greenhouse gases into the atmosphere [4]. The materials used are mostly determined by variables such as cost, availability, and the type of application, among others. Geopolymer concrete employs sustainable construction materials as binders. The locally available industry by-products are used as a binder instead of cement. Due to its use of abundant wastes and low greenhouse gas emissions, GPC is both economical and eco-friendly [5]. This research aims to study the effects of source materials and different concentrations of NaOH on the strength characteristics of GPC. In fly ash-based geopolymers, alkaline activators cause the silica and alumina in the source material to form a gel to enhance bonding between aggregates with any unreacted components.[6] stated that geopolymer concrete requires thermal curing at 40-70 degrees Celsius to faster the hydration process, therefore the specimens are cured between 24 and 48 hours in the oven. [7] studied characteristics of geopolymer concrete with different replacements of GGBS to flyash and found the increase of GGBS content improved strength and decreased workability. This research examines the compressive strength of specimens for two different binders 360 and 400 kg/m³ (replacing flyash with GGBS with 70-30, 60-40, and 50-50) with different A/B ratios (0.45 & 0.5) in line with an alkaline solution made of NaOH and Na₂Sio₂ and specimens were cured for 7 and 28 days (outdoor curing and oven curing at 60°C for 24 hours). Overall, 144 cubes were cast to determine compressive strength, in line with the workability of GPC. The findings have shown that GPC with appropriate strength may be produced by utilizing fly ash and GGBS combination in the outdoors, without the need for oven curing. However, there is less work conducted by various researchers on geopolymer concrete to determine mechanical properties with various replacements of GGBS and different molarities. This work would set a benchmark for future researchers in the field of geopolymer. It would provide a pathway for further studies of this material when a geopolymer concrete that was cured outdoors had a reasonable compressive strength.