The role of alkaline activator in geopolymerization of low-calcium fly ash based geopolymers
Inorganic polymers or simply geopolymers were synthesized in this study by the alkaline activation of local low-calcium (Class F) fly ash. The alkaline activator liquid used for the activation process was a mixture of sodium silicate (waterglass) and sodium hydroxide (NaOH) solution. The main pur...
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| Format: | Thesis |
| Language: | English |
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| Online Access: | http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/12843/1/p.%201-24.pdf http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/12843/2/Full%20Text.pdf |
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| Summary: | Inorganic polymers or simply geopolymers were synthesized in this study by the
alkaline activation of local low-calcium (Class F) fly ash. The alkaline activator liquid used for
the activation process was a mixture of sodium silicate (waterglass) and sodium hydroxide
(NaOH) solution. The main purpose of the research was to study the effect of the alkaline
activator content and the alkaline activator constituents (Waterglass and NaOH solution)
mixing ratio, on the compressive strength and on the microstructure of the resulted lowcalcium
(Class F) Fly ash-based geopolymer. The geopolymers were prepared at fixed
operation parameters, which were including: the concentration of NaOH solution (15M),
additional water (17% of the geopolymer weight), mixing time (15min), dilation time (24hr),
curing temperature (70°C), curing time (24hr), and aging time of (24hr). The alkaline activator
content was verified according to the Activator/Fly ash mass ratios utilized in the current
research, which were (0.3, 0.35, and 0.4), and verified the mixing ratios of the alkaline
activator constituents or waterglass/NaOH ratios were (0.6, 0.8, 1.00, and 1.2). The highest
compressive strength was obtained at highest alkaline activator content (Activator/Fly ash
=0.4). The compressive strength and the SEM data also showed that for each Activator/Fly ash
ratio (0.3, 0.35, and 0.4), an optimum waterglass/NaOH ratio of (0.8, 1.00, and 1.00
respectively); give the highest compressive strength and a homogenous, less porosity
microstructure with less unreacted fly ash spheres. XRD analysis showed that the formed
geopolymers at the optimum waterglass/NaOH ratios were mainly amorphous with presence of
crystalline phases existed in the original fly ash and some zeolitic phases were formed during
the geopolymerization process. The optimum compressive strength geopolymer (8.61 MPa,
Activator/Fly ash ratio = 0.4, and waterglass/NaOH =1.00), shows low thermal durability at
400°C, by the formation of macrocracks on the sample surface due to the water evaporation
and further deterioration and sintering process takes place at higher temperatures of 600 &
800°C. |
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