Impact of pozzolanic additives on compressive strength and elastic modulus of high-strength self-compacting concrete

Abstract This study investigates the effects of using sugarcane bagasse ash (SCBA) and Alccofine (AF) as partial cement substitutes in M60 grade high-strength self-compacting concrete (HSSCC), focusing on their mechanical properties from both microstructural and durability perspectives. The research prioritizes assessing the fresh property performance, compressive strength, elastic modulus, microstructural behaviour, porosity, and coefficient of sorptivity across four different mixture compositions. The SCBA and AF combinations demonstrated excellent self-compactability, aligned with EFNARC standards, and were well suited for complex reinforcement configurations. Among the mixtures, 10SCBA30AF consistently showed superior results, with a 15.2% increase in elastic modulus and improved strength at both 28 and 90 days, despite having a higher total porosity compared to other ternary HSSCC mixtures. This was due to the reduced pore connectivity and denser interfacial transition zone (ITZ), as confirmed by SEM analysis. The XRD results revealed significant calcium silicate hydrate gel formation and reduced unreacted clinker phases, highlighting the accelerated hydration process facilitated by ultrafine particles of AF and reactive silica of SCBA. The 10SCBA30AF mix also achieved a 47.27% decrease in sorptivity, thereby effectively resisting moisture penetration. Overall, the combination of SCBA and AF resulted in concrete with refined microstructures, enhanced mechanical properties, and a reduced sorptivity coefficient, demonstrating their potential as sustainable high-performance materials for durable infrastructure.