Plasticizing Geopolymer-Type Auspensions: A Challenge


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Title: Plasticizing Geopolymer-Type Auspensions: A Challenge

Author(s): L. Nicoleau, M. Pulkin, and T. Mitkina

Publication: Special Publication

Volume: 302


Appears on pages(s): 477-490

Keywords: geopolymer; high-alkalinity; silicate adsorption

Date: 6/1/2015

The composition of the aqueous solution in alkali-activated binders, i.e., the high alkalinity and the high ionic strength challenge chemists to design molecules exhibiting the same plasticizing effects as in cementitious materials. The highest difficulty probably lies in alkali-silicate activated systems due to the presence of multivalent silicate oligomers in solution. Reported here are new insights about the adsorption of polymers in presence of various concentrated electrolyte solutions in order to mimic the harsh conditions present in geopolymer pastes. In order to eliminate the problem of the reactivity of such systems, TiO2 nanoparticles were used as a model substrate. The adsorption of polymer molecules as well as the specific adsorption of monovalent and divalent ions is revealed. Those results are compared to the rheological characteristics of alkali-hydroxide or alkali-silicate activated geopolymers. The conclusions which can be drawn from the model system fit qualitatively very well with the classical slump tests done on real systems.