Cements 2013 Della Roy Lecture
Dr. Leslie J. Struble, Department of Civil Engineering, University of Illinois
Biography: Struble has been a member of the faculty at University of Illinois since 1989. She teaches courses related to composition, microstructure, and performance of building materials; and she carries out research and consulting activities involving various aspects of concrete performance. She was Associate Director of the Center for Advanced Cement Based Materials from 2000 to 2003. Prior to joining the faculty of the University of Illinois, Dr. Struble worked at the National Institute of Standards and Technology, Martin Marietta Laboratories, and California Portland Cement Company. Struble earned her BA in Chemistry from Pitzer College (1970), and her MS and PhD in Civil Engineering from Purdue University (1979 and 1987, respectively). She has authored or co-authored more than 140 publications dealing with various aspects of cement and concrete. In 2003 she received the ASTM Sanford E. Thompson Award for a paper on alkali-silica reaction. Struble is a member and a Fellow of The American Ceramic Society, where she has served as Chairman of the Cements Division and as Trustee and where she currently is an Associate Editor for the Journal of the American Ceramic Society. She is a member and a Fellow of the American Society for Testing and Materials, where she is Editor in Chief of the Journal of Advances in Civil Engineering Materials. She is a member and a Fellow of the American Concrete Institute.
Title: Calcium in Geopolymers
Abstract: The geopolymer system is being widely studied for many ceramic applications, not the least of which is a binder in structural concrete. Geopolymers form by reaction of a powdered aluminosilicate precursor with an aqueous alkali hydroxide solution. The precursor most widely studied is metakaolin, whose reaction occasionally forms a crystalline zeolite but in our experiments always forms an amorphous gel, whose molecular structure we are probing mainly with nuclear magnetic resonance (MAS-NMR). Calcium is often present in the reaction and is seen to speed up setting and increase strength of the geopolymer. When calcium is present, calcium silicate hydrate is presumed to form in addition to the geopolymer gel, although no direct experimental evidence for this phase is seen in the literature. Identifying calcium silicate hydrate in the presence of geopolymer gel is rather difficult, but we have successfully identified both phases using MAS-NMR. Evidence for this identification will be shown and discussed.