Examining the structural viability of recycled fine aggregates in sustainable concrete

This study investigates the potential of incorporating recycled fine aggregates (RFA) into sustainable concrete. In this research, a conventional compaction technique is utilized to establish the order of compressive strength and, consequently, to assess particle packing density in terms of weight within a specific cylindrical volume and evaluate workability, compressive and flexural strengths, splitting tensile strength, elasticity modulus, and microstructural properties (analyzed through XRD, SEM, and EDAX). The study found that RFA can improve concrete properties, hardened characteristics, and microstructure up to an optimum 25 % RFA replacement threshold (RFA 25). Beyond this value, concrete strength and microstructure deteriorate. RFA 25 exhibits significantly higher compressive (14.75 %), flexural (6.61 %), and splitting tensile (13.14 %) strengths compared with the reference concrete, along with a 5.71 % decrease in the modulus of elasticity. Lower replacement levels promoted pozzolanic reactions, enhancing strength through additional hydration products, whereas higher replacements reduced strength.