Influence of micro and nano eco-friendly materials on sustainable ultra high performance concrete properties

Abstract This study investigates the influence of micro- and nano-scale rice husk ash (RHA) and sugarcane bagasse ash (SBA) on the mechanical, durability, and microstructural performance of ultra-high-performance concrete (UHPC). Binary blends with micro-RHA (MRHA) and micro-SBA (MSBA) at 10–50% replacement, and ternary blends including nano-RHA (NRHA) and nano-SBA (NSBA) were compared to a control mix. Compressive strength, tensile strength, flexural strength, and modulus of elasticity were measured alongside durability tests (water permeability, chloride penetration, sorptivity, thermal and sulfate resistance). Optimal micro-scale replacements (20% MRHA and 20% MSBA) increased 28-day compressive strength by 10.5% and 15%, respectively, while ternary blends achieved up to 177.8 MPa, minimal permeability, and excellent sulfate resistance. SEM analyses confirmed matrix densification and enhanced C-S-H formation, demonstrating the synergistic benefits of micro- and nano-ashes as sustainable cementitious replacements for UHPC.