Setting and nanostructural evolution of metakaolin geopolymer. Issue 5 (16th March 2017)

• Record Type: Journal Article
• Authors: Chen, Xu; Sutrisno, Andre; Zhu, Lingyang; Struble, Leslie J.
• Is Part Of: Journal of the American Ceramic Society. Volume 100:Issue 5(2017)
• Page Start: 2285
• Page End: 2295
• Publication Date: 2017-03-16
• Subjects: geopolymers -- nuclear magnetic resonance -- set -- structure; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.14641
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: The nanostructural evolution during formation of geopolymers and its correlation with setting have not been well understood. In this study, penetration resistance and ultrasonic wave reflection tests were conducted to measure setting, and solid‐state 27 Al NMR and liquid‐state 29 Si NMR were used to examine nanostructural changes in a metakaolin geopolymer as a function of time. Aluminum was released rapidly during the first 10 hour after mixing and immediately condensed with silicate species in solution to form larger sized aluminosilicate oligomers, which then condensed to form large structural units. Our evidence suggests these units form near metakaolin particle surface. Smaller sized silicate ions in the sol phase then attach to these units to form a gel with a more interconnected network structure. The initial stage of this attaching process was seen to be associated with set, which in this mixture occurred at 15 hour.