The influence of fly ash characteristics and reaction conditions on strength and structure of geopolymers

• Published in: Construction & building materials Vol. 94; pp. 361 - 370
• Main Authors: Nikolic, Violeta, Komljenovic, Miroslav, Bascarevic, Zvezdana, Marjanovic, Natasa, Miladinovic, Zoran, Petrovic, Rada
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 30.09.2015; Elsevier B.V
• Subjects: Aluminosilicates; Aluminum silicates; Analysis; Assessments; Atomic structure; Building materials; Compressive strength; Construction materials; Fly ash; Geopolymer; Mechanical properties; Reactivity; Strength; United States; Fly ash; Geopolymer; Compressive strength; Reactivity
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2015.07.014

•Effects of FA characteristics and reaction conditions on geopolymer strength were studied.•Development of FA-geopolymer structure was studied using SEM/EDS and NMR analyses.•The correlation of FA characteristics, structure and strength of geopolymer was given.•Strength of geopolymers was correlated with a fraction of Al-rich structural units.•Rapid test for assessment of FA reactivity was evaluated. Reactivity of Class F fly ash (FA), development of strength, and structure of FA-based geopolymers, depending on the reaction conditions, were examined in this paper. The results of SEM/EDS and NMR analyses revealed that the composition of aluminosilicate gel changed during reaction, i.e. Si/Al atomic ratio decreased with the reaction time. Higher strength of geopolymers was associated with a higher fraction of aluminum rich structural units, higher crosslinking, and more compact structure. A rapid test for the assessment of FA reactivity and thus the applicability of FA for geopolymer synthesis was proposed.