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<p>This study investigates the thermo-mechanical behaviour of alkali-activated concrete (AAC) incorporating a binary binder of fly ash and ground granulated blast-furnace slag under elevated-temperature exposure. The primary objective is to evaluate the influence of sodium hydroxide concentration on mechanical performance, residual strength, and thermal conductivity. Three AAC mixes were prepared with constant sodium silicate content (8%) and varying sodium hydroxide concentrations of 8%, 9%, and 10%. Specimens were tested under ambient conditions and after exposure to 200&#xa0;°C and 400&#xa0;°C. Experimental evaluation included compressive strength, stress–strain response, residual capacity, mass loss, water absorption, and thermal conductivity. Microstructural characteristics were examined using scanning electron microscopy and energy-dispersive spectroscopy, while finite element modelling was employed to validate heat transfer behaviour. The results indicate that higher alkali concentration enhances geopolymerization, leading to improved strength and reduced porosity. The mix with 10% sodium hydroxide achieved a compressive strength of 53.62&#xa0;MPa and retained approximately 70% of its strength after exposure to 400&#xa0;°C. Thermal conductivity increased with alkali content, reflecting a denser microstructure, with values ranging from 1.58 to 2.57 W m<sup>−1</sup>·K<sup>−1</sup>. However, increased stiffness at higher concentrations resulted in relatively brittle behaviour under thermal loading, whereas the 9% mix exhibited a balanced response with improved ductility and thermal stability. Numerical simulations showed good agreement with experimental results, with deviations within 5%, and highlighted localized thermal gradients influenced by boundary conditions. Overall, the findings demonstrate that optimizing alkali concentration is essential for achieving a balance between mechanical integrity and thermal performance, supporting the application of AAC in heat-resistant and sustainable construction systems.</p>

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Experimental and numerical investigation of temperature-induced behaviour in fly ash–GGBFS alkali-activated concrete

  • 期刊论文

  • 发表日期：

    2026年7月25日

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  • Yellanki Deepti,
  • Sanjay Kumar,
  • Atrayee Bandyopadhyay,
  • Pramod Kumar

摘要

This study investigates the thermo-mechanical behaviour of alkali-activated concrete (AAC) incorporating a binary binder of fly ash and ground granulated blast-furnace slag under elevated-temperature exposure. The primary objective is to evaluate the influence of sodium hydroxide concentration on mechanical performance, residual strength, and thermal conductivity. Three AAC mixes were prepared with constant sodium silicate content (8%) and varying sodium hydroxide concentrations of 8%, 9%, and 10%. Specimens were tested under ambient conditions and after exposure to 200 °C and 400 °C. Experimental evaluation included compressive strength, stress–strain response, residual capacity, mass loss, water absorption, and thermal conductivity. Microstructural characteristics were examined using scanning electron microscopy and energy-dispersive spectroscopy, while finite element modelling was employed to validate heat transfer behaviour. The results indicate that higher alkali concentration enhances geopolymerization, leading to improved strength and reduced porosity. The mix with 10% sodium hydroxide achieved a compressive strength of 53.62 MPa and retained approximately 70% of its strength after exposure to 400 °C. Thermal conductivity increased with alkali content, reflecting a denser microstructure, with values ranging from 1.58 to 2.57 W m−1·K−1. However, increased stiffness at higher concentrations resulted in relatively brittle behaviour under thermal loading, whereas the 9% mix exhibited a balanced response with improved ductility and thermal stability. Numerical simulations showed good agreement with experimental results, with deviations within 5%, and highlighted localized thermal gradients influenced by boundary conditions. Overall, the findings demonstrate that optimizing alkali concentration is essential for achieving a balance between mechanical integrity and thermal performance, supporting the application of AAC in heat-resistant and sustainable construction systems.