PERFORMANCE OF NANO SILICA GEL PRODUCED FROM RISE HUSK ASH (RHA) IN CEMENTITIOUS MEDIA

Abstract

This study investigates the use of Nano-Silica Gel (NSG) derived from Rice Husk Ash (RHA) as a sustainable alternative in cement-based composites. RHA, rich in amorphous silica, is an eco-friendly source for NSG production, which can enhance cement performance and reduce environmental impact. Experimental tests were conducted on pastes and mortars by replacing cement with NSG dosages of 1%, 2%, 3%, and 5% to evaluate flowability, density, setting time, compressive strength, flexural strength, shrinkage, soundness, electrical resistivity, and pozzolanic activity. Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) were also used to analyze microstructural changes at 7, 28, and 90 days. Results showed that 1% NSG significantly improved compressive strength (53.9 MPa) and flexural strength (6.94 MPa) at 90 days, compared to the control mix. This improvement is due to the highly reactive nature of NSG, which accelerates the formation of calcium-silicate-hydrate (C-S-H) gel, enhancing the matrix and pore structure. However, higher NSG dosages (≥3%) decreased strength and stability due to increased water demand and particle agglomeration. Pozzolanic activity was moderate at 1–2% NSG but declined at 5%. The Frattini test confirmed moderate pozzolanic activity at lower dosages; however, the benefits diminished at the highest replacement level (5%). Lower NSG levels improved electrical resistivity, while higher dosages increased porosity. In conclusion, NSG derived from RHA could be a viable and effective supplementary cementitious material when used at optimal replacement levels. Specifically, a 1% NSG substitution shows the best balance of enhanced strength and other relevant properties. The use of RHA-derived NSG also contributes to sustainability goals by reducing the demand for cement, an energy intensive material. This work offers valuable insights into advancing sustainable practices in the construction industry by promoting waste utilization and reducing the carbon footprint associated with cement production.