| dc.description.abstract | The use of ordinary Portland cement is evident for centuries now especially in civil industries. Lacking of greener option with equal or enhanced properties forced consumers to ignore the shortcomings of ordinary Portland cement. Investigation of kaolin based geopolymer coating was aimed to not only increase the productivity and applications of
geopolymer but also to potentially replace the use of ordinary Portland cement in terms
of coating technology. Initial aim for this study was to prepare an optimum geopolymer
coating paste made up of kaolin, as the aluminosilicate source and alkaline activator
solution. The optimum mix design was mainly judged by its mechanical strength,
followed by physical, phase analysis and scanning electron microscopy micrographs as
crucial parameters of sodium chloride concentration, solids-to-liquid (S/L) ratio and
alkaline activator ratio was studied. Kaolin, the geopolymer source material was
characterized by using particle size analysis, phase, chemical composition, and scanning
electron microscopy testing. Kaolin geopolymer paste with 8 M sodium hydroxide
molarity, solids-to-liquid (S/L) ratio of 0.9 and alkaline activator ratio of 0.40 cured at 70
°C for 24 hours, gave highest strength values of 2.4 MPa (7 days), 2.98 MPa (28 days)
and 4.56 MPa (90 days). This mix design also proven to have good workability, density,
semi crystalline phase, and homogeneous compacted geopolymer matrix through
morphology micrographs, in agreement to strength values. Continues improvement of
kaolin geopolymer paste over time showed promising potentials towards preparation of
kaolin based geopolymer coating. To the best of our knowledge, no attempts have been
made previously to produce kaolin based geopolymer coating for lumber wood
application, thus making it a novel work. The geopolymer paste were then coated on most
unlikely substrate to investigate the extent of its bonding capabilities. This was evidently
studied through bonding, physical, mechanical and morphological results. Optimum
kaolin geopolymer coating successfully adhered to lumber wood substrate and provided
high strength value of 4.3 MPa (7 days), 4.9 MPa (28 days) and 5.96 MPa (90 days).
Early mechanical strength of kaolin geopolymer coated lumber wood differs from
mechanical strength exhibited by kaolin geopolymer paste due to moisture absorption
into substrate as supported by interfacial layer micro images. Hardness value was in
agreement with flexural strength of kaolin geopolymer coated lumber wood and phase
analysis of kaolin geopolymer paste. Zeolite peak contributes to high early strength
development but disrupts geopolymer structure over time that leads to drop in strength
upon sample age. Investigation of sample over different time period is proven to be
important for long term usage of geopolymer coating. Ultimately, this study clearly
demonstrated the processing and feasibility of kaolin geopolymer coating material. | en_US |
