Development of Geopolymer Paste Mixture made from Low-Calcium Fly Ash using Sodium Silicate and Potassium Hydroxide Combination as Activator

Author : Belen, Mae Khrystelle Manalo
Major Adviser : Laurio, Michael Vincent O.
Committee Members : Alfafara, Catalino G.; Borines, Myra G.; De Castro, Leandro T. 
Year : 2017
Month : June
Type : Thesis
Degree: BS
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Geopolymer technology is a promising emerging technology which can cater to sustainable development and solve waste problems. Geopolymerization is a reaction between an aluminosilicate source and a chemical activator. Geopolymer paste samples were made from different amount combinations of low-calcium fly ash, 10 M potassium hydroxide solution, and sodium silicate solution with Ms of 2.20. The samples underwent 24-hr setting time, 24-hr thermal curing at 60 °C, and 7-day ambient curing before compression testing. The factors considered in this study are the mass fractions of FA, KOH, and SS and the ratios SS/KOH and AA/FA, while the responses are compressive strength and workability (quantified by area factor using polar graph). The lowest and highest area factors obtained in the experiment are 1.00 and 58.78, respectively. The lowest and highest compressive strengths recorded are 0.31 MPa and 16.54 MPa, respectively. KOH, SS, SS/KOH and AA/FA were found to be significant terms in the statistical analyses for both responses. However, significant lack of fit existed. Characterization of fly ash and geopolymer pastes were done through XRD, SEM and FTIR analyses. By XRD analysis, the fly ash was found to be amorphous. SEM analysis showed that samples having better microstructure, with few pores and of compact structure, have high compressive strength. FTIR spectroscopy reported that silicon links and oligomers are present like dioxosilane, DOSi⁺, HOSi⁺ , Si₄ and Si₃. The cost of the least workable, most workable, LCS, HCS, and blank samples are 15.86, 19.13, 18.97, 19.95, and 10.44 pesos per kg FA utilized.

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