ABSTRACT
The current study focused on the utilization of local clay for synthesis
and characterization of meta-kaolin based geopolymers with and without
nano-silica. The control geopolymers, for a compressive strength of 30 MPa,
were optimized by using Liquid/Solid ratio of 0.55, NaOH concentration of 10 M
and curing at 80°C. The nano silica was added in an extended range of 1%, 2%,
3%, 5%, 7% and 10%. The synthesized nano-silica metakaolin based geopolymers was investigated by using compressive strength, XRD, XRF, FTIR, SEM, MIP, TG,
UV/VIS spectroscopy, in addition to density, water absorption and initial
setting times. The results indicated an increase in the compressive strength
value with the incorporation of nano-silica in geopolymer mixes until the
optimum percentage of 5%, while the 10% addition of nano-silica decreased the
compressive strength by 5% as compared to the control geopolymer. The increase
in the compressive strength was accredited to the increase in the content of
N-A-S-H gel and the amorphous structure as shown by XRD and FTIR analysis. In
addition, the optical transmittance analysis, MIP and SEM scans along with the results
of density and water absorption have clearly shown the densification of the
matrix formed for the optimal percentage of nano-silica. However, the initial
setting time was found to reduce substantially with increase of nano-silica
content. Moreover, the TG results have shown the 5% nano-added geopolymers to
have greater thermal stability as compared to reference geopolymers.
Finally, the adopted methodology in this research has shown that 5%
nano-silica, is the optimal result for the synthesis and the production of
local meta kaolin based geopolymer, with regard to the improvement of physical
properties, micro structure and compressive strength.