PSI - Issue 70

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

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reduced setting times (110– 607 min). Fly ash-slag blends reach 108 MPa at 28 days; Ca(OH)₂ or UFFA alone yields low strength; UFFA/slag boosts strength by 44%/275%. GPC strengths (30.4–71.4 MPa) exceed OPC (27.5–68.6 MPa); tensile strength comparable (f_st = 0.08 f_cs^0.92). GRAC with 50% GGBS/50% fly ash achieves 51.4% higher strength than OPC; GGBS boosts stiffness, reduces ductility. 3% superplasticizer in 100% GGBS GPC yields 40.2 MPa (+10.4%); 50% GGBS/50% fly ash boosts tensile strength by 27.6%. 16M NaOH and 100°C curing yield 43.6 N/mm²; GGBS enhances strength via calcium silicate hydrate gel. 30% RHA, 20% GWP, 10% VPP optimize strengths; higher substitutions reduce compressive strength.

Khan et al. (2016)

Fly ash-slag blends as a high-strength, ambient- cured, eco -friendly alternative.

Ambient curing; not detailed on workability specifics.

Ramujee & Potharaju (2017)

Sustainable engineered material with lower CO₂ emissions, suitable for construction.

Heat curing at 60°C for 24 hours; OPC water - cured for comparison.

Xie et al. (2019)

Eco - friendly GRAC with 100% recycled aggregates, high- performance substitute for civil engineering Structures.

Fly improves workability; 0.5 W/B ratio balances workability and strength. Superplasticizers improve workability and density; not detailed on curing specifics. 100°C curing boosts early strength; ambient curing yields lower results; workability decreases with GGBS. 50% VPP boosts workability by 38.5%; RHA, GWP reduce it by up to 23.1% and 30.8%. ash

Gupta et al. (2021)

Sustainable GGBS - fly ash GPC with optimized superplasticizer dosage.

Thapa et al. (2024)

Reduces carbon emissions; suggests mechanized mixing for practical, cost effective use.

Tahwia et al. (2024)

Sustainable EGC using waste materials (RHA, GWP, VPP), balancing performance and eco -friendliness.

3. Durability in Aggressive Environments The release of silicic acid (Si(OH) 4 ) and the depolymerization of the aluminosilicate network structure may be linked to the acid attack in geopolymer concrete. In contrast, it is well known that OPC concrete degrades when exposed to an acidic environment (pH <6.5). The cementation particles and calcium-rich aggregate in OPC concrete dissolve when exposed to acid, which results in its deterioration. Despite the reduction of strength (Table 2) due to the acid attack, geopolymer concrete performs well compared to OPC. Table 2. Key Findings on the Reduction of GPC Compressive Strength Due to Sulphuric Acid Exposure Across Multiple Studies Study Strength reduction of GPC subjected to sulphuric acid Abhilash et al., 2017 On a 28- day immersion in a 2% sulphuric acid solution, the geopolymer concrete's compressive strength was 5.72% lower. Çevik et al., 2018 After a month - long immersion in a 5% sulphuric acid solution, the geopolymer concrete's compressive strength was 19% lower. Valencia-Saavedra et al., 2020 After a 28- day immersion in a 1 molar concentration of sulphuric acid solution, the geopolymer concrete's compressive strength was 20% lower . (Hewayde et al., 2006) investigated the impact of geopolymer cement on the microstructure and sulphuric acid resistance of concrete. The research highlights the global issue of concrete sewer pipe corrosion caused by biogenic sulphuric acid, which results from hyd rogen sulphide (H₂S) produced by sulphate -reducing bacteria in anaerobic wastewater conditions. The sulphuric acid reacts with hydration products in concrete, forming gypsum and ettringite, leading to volume expansion, microcracking, and structural degradation. The study reveals that geopolymer cement enhances concrete's resistance to sulphuric acid. Microstructural analyses (XRD, SEM) showed denser matrices and the formation of new hydration products like calcium-magnesium-aluminium-oxide silicates (CMAOS), which contribute to improved durability and strength. The study concludes that geopolymer cement is a promising solution for enhancing concrete durability in acidic environments, though its effectiveness depends on the binder type and replacement level. Because of its distinct chemical structure, which excludes delicate hydration products like gypsum