Comparative Mechanical Performance of High-Strength Concrete Incorporating Locally Sourced Rice Husk Ash Nano-Silica and Imported Nano-Silica

Abstract

This study comparatively evaluated the mechanical performance of high-strength concrete incorporating locally sourced rice husk ash nano-silica and imported nano-silica as partial cement replacement. The research responds to the heavy reliance of nano-silica-modified concrete production on costly, industrially synthesized, imported material, and examines whether a locally producible alternative derived from an abundant agricultural waste can deliver comparable results. Rice husk ash nano-silica was produced through controlled combustion of rice husk followed by alkaline dissolution and acid precipitation, and its silica content, specific surface area, and specific gravity were determined alongside those of commercially sourced imported nano-silica. Twenty-seven high-strength concrete mixes were proportioned using a particle-packing-based mix design, incorporating each nano-silica type at replacement levels of 0 to 20 percent across three water-binder ratios, and evaluated for workability and for compressive, splitting tensile, and flexural strength at 7, 14, and 28 days. Both nano-silica types achieved an optimum replacement level of approximately 15 percent, beyond which strength declined. At this optimum, concrete containing imported nano-silica achieved a slightly higher 28-day compressive strength than concrete containing rice husk ash nano-silica, though statistical analysis found no significant interaction between nano-silica source and replacement level. The findings indicate that rice husk ash nano-silica is a mechanically viable substitute for imported nano-silica in high-strength concrete production, supporting its consideration as a lower-cost, locally sourced alternative, particularly in rice-producing regions.