Implementing modified triple blend technique for enhancing the microstructure of recycled aggregate with M-sand in concrete

This investigation explores the behavior of recycled aggregate concrete (RAC), employing a triple blend technique aimed at enhancing concrete properties with M- Sand. The triple blend comprises fly ash, ground granulated blast furnace slag (GGBS), and Alccofine, serving as partial replacements for cement of 60% to improve overall concrete performance when combined with recycled concrete aggregate (RCA). Concrete samples were then manufactured with varying RCA percentages, ranging from 25 to 100%. The study investigated the strength properties of the mix, including compressive strength, tensile strength, flexural strength, impact strength, bond strength, and overall concrete quality through non-destructive testing. Additionally, these samples underwent microstructural studies and phase assemblage analyses, including scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy tests. These analyses were conducted to determine the pore structure and mineralogical composition of the RAC. The results indicate that an increase in RCA content in the concrete mix tends to reduce compressive strength, primarily due to weaker bonding with the cement paste. However, this drawback can be partially mitigated by incorporating mineral admixtures in a modified triple mix blend. This modification leads to improved hydration, enhanced bonding, favourable morphology, and a refined pore structure. This study reveals that SRAC exhibits superior strength compared to Raw RAC, with considerable increase at 28 days and maintaining comparable strengths to CC at 28 days. This study suggests potential for sustainable structural concrete production with 25 to 50% RCA replacement and supplementary cementitious materials (SCM) incorporation.