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

Author : Saturno, Mary Joy Mendez
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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Geopolymerization is the chemical reaction between aluminosilicates source and activator. In this study, mixture design for geopolymer paste derived from class F fly ash and sodium hydroxide-sodium silicate as the alkali activator was developed. Massfractions of fly ash, Na₂SiOc with silicate modulus of 2.2 and 10 M NaOH were considered while compressive strength and workability were the responses used. The samples were subjected to 24 hours pre-curing, 24 hours of thermal curing at 60 °C and seven days ambient curing prior to compressive testing. Based from the compositional and XRD analysis of the fly ash, the sample was verified as class F fly ash and amorphous in nature. The lowest and highest area factors obtained were 1.00 and 39.07 respectively while the lowest and highest compressive strength obtained were 0.30 MPa and 9.65 MPa respectively. Fly ash, Na2SiO3 and NaOH have significant effects in compressive strength and workability with fly ash as the dominating main effect. Mass ratios of alkali activator to fly ash and Na₂SiO₃ to NaOH were also considered where both ratios were found to be significant factors. SEM micrographs showed that highest compressive strength resulted from compact structure and fewer amounts of unreacted fly ash and FTIR results confirmed the presence of Si-O-Si and Si-O-Al which are indicators of the presence of the geopolymer chain. Material costing was done based from the industrial cost of all the raw materials cost and the prce of geopolymers with lowest and highest compressive strength are Php. 10.42 and Php. 11.02 respectively.

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