Development of thermally efficient high volume fly ash-rubberized concrete using nano silica: A sustainable solution for energy-sensitive construction

Abstract

The construction industry faces increasing pressure to adopt sustainable materials that not only minimize environmental impact but also improve thermal efficiency in buildings and pavements. Conventional concrete, despite its structural strength, is thermally inefficient and contributes significantly to CO₂ emissions. While previous studies have explored either high-volume fly ash (HVFA) or rubberized concrete independently, this study presents a novel integration of HVFA with crumb rubber (CR) and nano silica (NS) to achieve both environmental and thermal performance goals. Additionally, it incorporates computational fluid dynamics (CFD) simulation to evaluate heat transfer behavior—an approach not commonly employed in similar material systems. This study addresses these limitations by developing a High-Volume Fly Ash Rubberized Concrete (HVFA-RC) incorporating 50 % fly ash as partial cement replacement, crumb rubber (0–30 %) as fine aggregate substitute, and 2 % nano silica by weight of binder to improve early-age strength and microstructure. Five mix designs were tested for mechanical, durability, and thermal properties, and further analyzed using CFD-based simulations in ANSYS CFX. Results revealed that increasing CR content reduced compressive strength and increased porosity; however, the addition of NS mitigated these effects by densifying the matrix. The optimized mix (C30N3) exhibited the lowest thermal conductivity (0.87 W/m·K), reduced thermal expansion (6.17 × 10⁻⁶/°C), and minimal heat transfer coefficient (5 W/m²·K), indicating superior insulation performance. This research demonstrates the practical feasibility of producing multifunctional concrete from industrial by-products and nanomaterials. The proposed composite offers enhanced thermal resistance and sustainability, making it a promising candidate for energy-efficient and thermally sensitive construction applications.