PSI - Issue 70

Ravi Malik et al. / Procedia Structural Integrity 70 (2025) 682–689

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and ettringite, the material also exhibits exceptional resistance to sulphate and acid attacks (Rangan, 2009). According to long-term research, geopolymer concrete either maintains or gains strength over time; specimens that are ambient cured do so more slowly than those that are heat-cured. The long-term performance of fly ash-based geopolymer concrete (FA-GPC) in maritime environments is examined by (Chindaprasirt & Chalee, 2014), with particular attention paid to the effects of sodium hydroxide (NaOH) concentrations (8M to 18M) on compressive strength, steel corrosion, and chloride penetration. Higher NaOH concentrations (8 – 18 molar) increased compressive strength during three years in a tidal zone; strength somewhat decreased at 18 M, but 14 – 16 M peaked at 40.3 MPa. Despite having a lower beginning strength, chloride diffusion coefficients were lower than in Portland cement concrete. Overall durability in marine settings was improved by higher NaOH's greater chloride binding capability. Chloride-induced corrosion of reinforcement in low-calcium fly ash-based geopolymer concrete (GPC) is investigated by (Babaee & Castel, 2016). Over the course of 11 months of wetting/drying cycles in a 35 g/L NaCl solution, the study tracks corrosion parameters — open circuit potential, polarization resistance, and Tafel slopes — using a blend of Class F fly ash and slag. According to the results, GPC performs electrochemically and polarization-resistantly similarly to Portland cement concrete (PCC) in conditions that are high in chloride. However, because of the lower pH and different Tafel constants (B=13-20 for passive, 45-58 for active vs. 52 and 26 for PCC), the conventional corrosion severity categories for PCC might need to be recalculated for GPC. Electrochemical results are confirmed by gravimetric mass loss, which shows consistent and pitting corrosion patterns similar to PCC. The durability of geopolymer concretes made from fly ash and granulated lead smelter slag (GLSS) is examined by (Albitar et al., 2017), in comparison to conventional Ordinary Portland Cement (OPC) concrete. In order to evaluate characteristics like compressive strength, water absorption, porosity, sorptivity, and mass loss, the materials are exposed to chemical solutions for nine months. OPC concrete has lower initial water absorption and sorptivity, according to the results, but geopolymer concretes perform better when exposed to chemicals, especially sulfuric acid, which lowers OPC strength by 26.6% compared to 10.9% for fly ash and 7.3% for GLSS. Due to sodium hydroxide leaching, sodium sulphate has a major impact on geopolymer concretes, indicating that other activators can improve performance. Because of internal pressures from chloride and sulphate crystallization, wetting-drying cycles show varying strength. Despite OPC's benefit in reducing water infiltration, geopolymer concretes have greater chemical stability overall, indicating their potential for long-lasting construction applications. The study emphasizes the necessity of more investigation into geopolymer binders' optimization. The durability of fly ash-based geopolymer concrete mixed with Ordinary Portland Cement (OPC) as a calcium source (0%, 10%, 20%, or 30% replacement) is investigated by (Mehta & Siddique, 2017). The concrete is exposed to 2% sulfuric acid for a maximum of 365 days. Using SEM, EDS, and XRD studies, the study assesses microstructural alterations, mass loss, and retention of compressive strength. According to the results, the addition of OPC increases the compressive strength of unexposed specimens because it causes calcium silicate hydrate (C-S-H) to form alongside alumina-silicate polymers. The highest strength (55 MPa) was obtained with 20% OPC. Though higher OPC levels (20%, 30%) enhance deterioration owing to calcium sulfate production, resulting in mass losses of 26.11% and 34.59%, respectively, compared to 12.97% at 0% OPC, acid exposure shows that 10% OPC retains the maximum strength (52% at 365 days). Denser structures with 10% OPC are confirmed by microstructural investigation; however, higher OPC levels worsen sulfate assault, resulting in the formation of calcite and anhydrite. According to the study's findings, 10% OPC balances strength and durability while optimizing acid resistance, providing a sustainable substitute for traditional concrete. The durability of geopolymer concrete (GPC), an environmentally friendly substitute for ordinary Portland cement (OPC) concrete, is examined in "A Review" by (Wong, 2022). The study assesses GPC's resistance to abrasion, acid assault, heat, and chloride penetration. Results show that GPC has equivalent abrasion resistance to OPC concrete, low to moderate chloride ion penetrability, greater acid resistance because of stable aluminosilicate bonding, and excellent compressive strength at ideal elevated temperatures (up to 600°C). Fibers, micro-silica, and nano-silica are examples of additives that improve durability by lowering porosity and cracking. Variable characteristics and thermal degradation above threshold temperatures provide difficulties, though. Although extended exposure to heat or acid increases porosity, GPC exhibits dense structures morphologically. GPC provides superior durability in harsh settings when compared to OPC. In order to improve GPC's practical acceptance, the review points out a research gap in the use of atypical precursors, such as heavy metal-contaminated clay, and suggests additional research on solid alkali activators, long-term performance, and structural applications.