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Effects of Precursor Nanostructure on Geopolymer Structure and Properties

Effects of Precursor Nanostructure on Geopolymer Structure and Properties Leslie J. Struble , University of Illinois at Urbana-Champaign, DMR 1008102.

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Effects of Precursor Nanostructure on Geopolymer Structure and Properties

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  1. Effects of Precursor Nanostructure on Geopolymer Structure and Properties Leslie J. Struble, University of Illinois at Urbana-Champaign, DMR 1008102 The cement industry produces the second highest carbon dioxide emissions. Currently there is a big push to produce more sustainable and environmentally friendly alternative cements. One of the leading alternatives that shows considerable promise to replace portland cement as the binder in structural concrete is geopolymers, a class of materials produced by reaction of an amorphous aluminosilicate precursor with an alkali hydroxide solution. Geopolymers significantly reduce the amount of greenhouse gas emissions. The technology is receiving much attention worldwide but so far very little application. The objective of the work proposed here is to determine how chemical composition and molecular structure of the precursor affect the nanostructure, microstructure, and engineering behavior of the geopolymer reaction products, mainly focusing on high lime fly ash. This proposal also responds to the NSF Materials World Network solicitation through collaboration with Prof. Lauren Gómez-Zamorano of the Universidad Autónoma de Nuevo Leon (UANL) in Mexico. Figure 1 represents the stages in formation of geopolymers. In the first stage, dissolution, a solid precursor, typically an amorphous aluminosilicate (often calcined kaolin) is dissolved in a high pH solution (typically a concentrated solution of NaOH in water). In the next stages the dissolved species rearrange to form a gel and finally a well polymerized aluminosilicate, which may be compared to an amorphous zeolite. The kinetics of dissolution mainly control the setting. The details of the gelation and polymerization stages control the microstructure of final product, and therefore its strength and stiffness. This project is new and has no results to report at this time. • Figure 1. Conceptual model of geopolymerization (Duxson et al., Journal of Material Science, Vol. 42 2007)

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