The link to the web site for research results and publications of the geopolymer group at University of Illinois, Urbana-Champain, USA, lead by Prof. W. Kriven, is the following:
A paper titled
MICROSTRUCTURE AND MICROCHEMISTRY OF FULLY-REACTED GEOPOLYMERS AND GEOPOLYMER MATRIX COMPOSITES
Waltraud M. Kriven, Jonathon L. Bell and Matthew Gordon The University of Illinois at Urbana-Champaign, Department of Materials Science and Engineering 1304 W. Green St., Urbana, IL 61801,USA
has been published in CERAMIC TRANSACTIONS, 2003.
it is available at:
The very interesting conclusion reads as follows:
“CONCLUSION: The processing, intrinsic microstructure and properties of geopolymer materials and geopolymer composites have been investigated. Curing of geopolymers was achieved by one of three routes, viz., pressureless curing, warm pressing, and curing in a high-pressure autoclave. The materials were fabricated at ambient temperatures up to (40-80°C). The work has focused on elimination of entrapped air, increased degree of reactivity, improvement in dissolution chemistry and attainment of adequate workability. Composites have been made and tested using basalt fiber weaves and chopped basalt fibers. Using fiber reinforcement, the bending strength and work of fracture of geopolymer materials have been increased from an average of 2.8 MPa to 10.3 MPa and from 0.05 kJ/m 2 to 21.8 kJ/m2, respectively. Electron microscopy techniques (SEM, TEM/EDS, in situ hot stage TEM) were used to study the effect of processing variables on microstructure. The microstructure of fully reacted geopolymers was sponge-like and consisted of nanoparticulates separated by nanopores whose features are of the order of ≤10 nm. The local microchemistry of fully reacted geopolymer frequently observed corresponded to a silica (SiO2) to alumina (Al2O3) ratio of 4:1. This is sometimes called the polysialate siloxo (PSS) composition. In situ, hot-stage TEM observations made during heating for 4 h up to 1000°C showed that the nanosized microstructure was stable, although continuous evolution of (presumably) H2O was noticed upon heating in the hot stage TEM. “