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<p>This study investigates the feasibility of recycled concrete fine aggregate (RFA) as a green alternative to river sand (RS) as a replacement for structural grade concrete as per UN Sustainable Development Goal 12. The aim was to evaluate the effects of RFA replacement on the workability, compressive strength, and microstructure of fresh concrete. Experimental blends, divided into five groups (A to E), were tested for five levels of substitution (0, 25, 50, 75, and 100%) of RS by RFA. Groups A and B were aimed at slumps of 75&#xa0;mm and 100&#xa0;mm, respectively, whereas Groups C and D included filtered aggregates, with Group D including additional water to simulate the saturated surface dry (SSD) condition of aggregates. In SSD, the aggregates were saturated with water internally, and were made to surface-dry condition to regulate the water-to-cement ratio. Group E utilized a superplasticizer in place of extra water to meet the desired slump. The results showed that Group E mixtures alone satisfied both workability and strength requirements, with E5 (100% RFA) performing best. Microstructural characterization using EDX and FESEM attested to an increased content of C-S–H gel and decreased Ca/Si ratio, both of which aided in increased strength. Thermogravimetric analysis showed increased thermal stability to 750&#xa0;°C. The E5 mix additionally demonstrated a modest decrease in CO₂ emissions and cost, marking its environmental and economic feasibility. The research concludes that 100% RS replacement with RFA is viable for structural concrete, providing a sustainable option for the future. </p>

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Recycled concrete fine aggregate: a sustainable substitute for river sand in fresh concrete

  • 期刊论文

  • 发表日期：

    2025年6月8日

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  • Anasna Kareem,
  • Dipak Kumar Sahoo,
  • S. Ramadass

摘要

This study investigates the feasibility of recycled concrete fine aggregate (RFA) as a green alternative to river sand (RS) as a replacement for structural grade concrete as per UN Sustainable Development Goal 12. The aim was to evaluate the effects of RFA replacement on the workability, compressive strength, and microstructure of fresh concrete. Experimental blends, divided into five groups (A to E), were tested for five levels of substitution (0, 25, 50, 75, and 100%) of RS by RFA. Groups A and B were aimed at slumps of 75 mm and 100 mm, respectively, whereas Groups C and D included filtered aggregates, with Group D including additional water to simulate the saturated surface dry (SSD) condition of aggregates. In SSD, the aggregates were saturated with water internally, and were made to surface-dry condition to regulate the water-to-cement ratio. Group E utilized a superplasticizer in place of extra water to meet the desired slump. The results showed that Group E mixtures alone satisfied both workability and strength requirements, with E5 (100% RFA) performing best. Microstructural characterization using EDX and FESEM attested to an increased content of C-S–H gel and decreased Ca/Si ratio, both of which aided in increased strength. Thermogravimetric analysis showed increased thermal stability to 750 °C. The E5 mix additionally demonstrated a modest decrease in CO₂ emissions and cost, marking its environmental and economic feasibility. The research concludes that 100% RS replacement with RFA is viable for structural concrete, providing a sustainable option for the future.