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.
