Towards Sustainable Ultra-High-Performance Concrete: Role of Nano Rice Husk Ash and Nano Sugarcane Bagasse Ash

Abstract

Ultra-high-performance concrete (UHPC) has gained considerable attention owing to its superior mechanical properties and durability; however, its performance can be further enhanced by incorporating nanoscale supplementary cementitious materials. This study investigates the effects of nano rice husk ash (NRHA) and nano sugarcane bagasse ash (NSCBA) on the mechanical and durability performance of ultra-high-performance concrete (UHPC) incorporating end-hooked steel fibers. Both nanomaterials were produced through controlled calcination at 700 °C for 3 h, followed by ball milling to achieve nano-sized particles, ensuring high pozzolanic reactivity and effective dispersion. UHPC mixtures were prepared with varying nano contents, and a comprehensive experimental program was conducted to evaluate the compressive strength, splitting tensile strength, flexural strength, and sorptivity at different curing ages.

The results demonstrated that the incorporation of NRHA and NSCBA significantly enhanced the mechanical performance of UHPC at both early and later ages. At 7 and 28 d, the compressive, splitting tensile, and flexural strengths showed notable improvements compared to those of the control mixture, with optimum nano contents yielding the highest strength gains. In particular, mixtures containing an intermediate dosage of NRHA exhibited the highest enhancements in tensile and flexural performance, indicating improved crack-bridging efficiency and fiber–matrix interaction. Durability assessment based on sorptivity measurements at 28 days revealed a substantial reduction in capillary water absorption for nano-modified UHPC, with NRHA-based mixtures showing the greatest improvement owing to pronounced pore refinement and matrix densification. Overall, the findings confirm that the use of agricultural waste-derived nanomaterials can effectively improve both the mechanical and durability properties of UHPC. Among the investigated mixtures, NRHA at the optimum dosage demonstrated superior overall performance, highlighting its potential as a sustainable and high efficiency nanoadditive for advanced UHPC applications.