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<p>This study investigates the optimization of strength and durability parameters of fly ash (FA) and ground granulated blast furnace slag (GGBFS)-based geopolymer concrete (GPC) incorporating nano-silica, activator aging, and carbonation curing. A central composite design (CCD) was employed with four key factors: FA: GGBFS ratio, nano-silica content, activator aging, and carbonation CO₂ concentration. The responses studied were compressive strength, water absorption, porosity, and carbonation depth. Experimental results showed that compressive strength ranged between 23.5 and 69.1&#xa0;MPa, water absorption between 1.6 and 11.9%, porosity between 7 and 22%, and carbonation depth between 0 and 18&#xa0;mm. ANOVA analysis identified FA: GGBFS ratio and nano-silica dosage as the most influential factors for strength and porosity, while carbonation concentration dominated carbonation depth. SEM confirmed that slag-rich, nano-silica–modified mixes exhibited dense gel matrices with fewer cracks, while XRD revealed the characteristic amorphous hump of geopolymer gels and, together with SEM observations, supported the coexistence of N–A–S–H and C–A–S–H gels in optimized mixes. Linear regression models achieved high accuracy (R² &gt; 0.9) for compressive strength, porosity, and water absorption, while ensemble methods (e.g., Random Forest, Gradient Boosting) were more effective in capturing the nonlinear trends of carbonation depth (R² = 0.85). The findings demonstrate that an optimal binder ratio (40–60% FA with 60–40% GGBFS), 3–4% nano-silica, moderate activator aging (12–24&#xa0;h), and controlled CO₂ curing (25%) yield high-performance and durable GPC. This integrated experimental, microstructural, and ML-based approach provides a sustainable pathway for developing low-carbon, high-strength concretes tailored to Indian conditions.</p> Graphical abstract <p></p>

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Strength and Durability Optimization of Geopolymer Concrete Using Nano-Silica and CO₂ Curing

  • 期刊论文

  • 发表日期：

    2026年4月18日

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  • Sandeep Singh,
  • A. K. Dasarathy,
  • Jagdeep Singh,
  • S. Vanitha,
  • Priyadarshi Das,
  • Gaurav thakur,
  • Priyanka Singh

摘要

This study investigates the optimization of strength and durability parameters of fly ash (FA) and ground granulated blast furnace slag (GGBFS)-based geopolymer concrete (GPC) incorporating nano-silica, activator aging, and carbonation curing. A central composite design (CCD) was employed with four key factors: FA: GGBFS ratio, nano-silica content, activator aging, and carbonation CO₂ concentration. The responses studied were compressive strength, water absorption, porosity, and carbonation depth. Experimental results showed that compressive strength ranged between 23.5 and 69.1 MPa, water absorption between 1.6 and 11.9%, porosity between 7 and 22%, and carbonation depth between 0 and 18 mm. ANOVA analysis identified FA: GGBFS ratio and nano-silica dosage as the most influential factors for strength and porosity, while carbonation concentration dominated carbonation depth. SEM confirmed that slag-rich, nano-silica–modified mixes exhibited dense gel matrices with fewer cracks, while XRD revealed the characteristic amorphous hump of geopolymer gels and, together with SEM observations, supported the coexistence of N–A–S–H and C–A–S–H gels in optimized mixes. Linear regression models achieved high accuracy (R² > 0.9) for compressive strength, porosity, and water absorption, while ensemble methods (e.g., Random Forest, Gradient Boosting) were more effective in capturing the nonlinear trends of carbonation depth (R² = 0.85). The findings demonstrate that an optimal binder ratio (40–60% FA with 60–40% GGBFS), 3–4% nano-silica, moderate activator aging (12–24 h), and controlled CO₂ curing (25%) yield high-performance and durable GPC. This integrated experimental, microstructural, and ML-based approach provides a sustainable pathway for developing low-carbon, high-strength concretes tailored to Indian conditions.

Graphical abstract