PSI - Issue 70

C. Manoj Prabhu et al. / Procedia Structural Integrity 70 (2025) 207–214

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1.Introduction Over the last few decades, the world has experienced challenges as a result of natural resource depletion and environmental degradation. Rapid industrialization, urbanization, and population expansion have boosted demand for housing, resulting in greater use of concrete materials such as cement (Prasad et al., 2025). The production of cement generates about 8% of global CO₂ emissions (Raut et al., 2023). The construction industry uses sustainable practices, such as green technologies that reduce greenhouse gas emissions from cement production, to mitigate its environmental impact (Chary et al., 2024). Geopolymer concrete (GPC) is an environmentally friendly alternative created from industrial byproducts that provides a long-term, low-carbon solution in the absence of cement. It is made from aluminosilicate-rich materials like fly ash and slag mixed with an alkaline solution, making it a possible alternative to regular concrete (Mathew et al.,2013) The activator liquid is essential in the polymerization process, facilitating the formation of a cementitious substance referred to as an inorganic polymer (Shebli et al., 2023). Geopolymer sustainable concrete employs various supplementary cementitious by-products as binders, including fly ash (Davidovits, 2013), metakaolin (Lakshmi Deepak & Vara Lakshmi, 2019), rice husk ash (Y. Jie et al., 2013; Sudharsan & Sivalingam,2019), silica fume (Okoye et al., 2017; Desai et al., 2018), GGBS (Sangeetha, 2015), and palm oil fuel ash (Amran et al., 2021). The geochemical process in concrete is predominantly influenced by the concentration of hydroxide and silicate activators, such as sodium hydroxide and sodium silicate. The compressive strength of geopolymer concrete (GPC) is influenced by the molarity of the alkaline solution (Chaithanya et al., 2020). The primary function of the alkaline activator is to solubilize silicon and aluminium in the raw ingredients, facilitating polymerization. This inorganic polymer, when combined with aggregates, produces concrete akin to OPC based mixtures while diminishing CO₂ emissions (Kustirini et al., 2021 ). Portland pozzolana cement (PPC) is frequently combined with fly ash, which is widely acknowledged as a potent supplemental cementitious ingredient with ecological advantages. Geopolymer concrete, an alternative devoid of cement, is manufactured with fly ash as the primary binder. Fly ash's silicon and aluminium are activated by an alkaline solution to generate a geopolymer substance. (Harikaran et al., 2023: Aleem & Arumairaj, 2012). This study proficiently use fly ash as a binder in the absence of Cement. Bennet et al. (2013) and Vidhya et al. (2013) investigated the economic implications and alternative materials for Cement -based and geopolymer concrete. Research proved that using fly ash and GGBS as binders in GPC instead of cement conserves carbon emissions and increases environmental sustainability (Sangeetha, 2015; Bennet et al., 2013). These materials improve concrete's resistance to chemical attacks, resulting in greater durability. Furthermore, by lowering the heat of hydration, they reinforce the concrete, enhancing long-term performance and reducing the risk of thermal cracking (Mudigonda et al., 2024).Sustainable geopolymer concrete using low-calcium fly ash has poorer mechanical strength, increased porosity, a longer setting time, and a shorter durability (Chithambar et al., 2023; Ganesh & Muthukannan, 2018).To address these challenges, researchers investigated replacing fly ash with rice husk ash (RHA), which contains around 95% silica and improves mechanical characteristics (Nuaklong et al., 2020). RHA has a low alumina content (less than 2%), but its high silica content raises the Si/Al ratio, increasing strength (Komnitsas and Zaharaki, 2007). However, an extremely high Si/Al ratio can decrease strength (Songpiriyakij et al., 2010). Fletcher et al. (2005) hypothesized that maintaining an appropriate Si/Al ratio increases mechanical performance. RHA additionally improves concrete durability. According to studies, concrete containing up to 15% RHA resists sulfate and chloride assaults while retaining its surface integrity (Sangeetha, 2015; Sensale, et al.,2010). At 20% replacement, it increases resistance to acid, chloride penetration, and corrosion while also performing well in sorptivity tests (Prasanna & Pazhani, 2015). Vieira et al. (2020) suggested that RHA increases concrete density while limiting chloride ion and acid infiltration via the creation of calcium silicate hydrate (C-S-H) gel. GPC's raw material selection is determined by availability, application, and cost. Geopolymer concrete is ideal for precast constructions and infrastructure projects due to its high early strength.