Paper Number
MC4 

Session
Rheology of Soil, Mud and Construction Materials

Title
Kinetic modeling of the rheological extent of reaction in model geopolymer gels

Presentation Date and Time
October 10, 2022 (Monday) 10:50

Track / Room
Track 7 / Ontario

Authors (Click on name to view author profile)

1. Mills, Jennifer N. (University of Delaware, Chemical and Biomolecular Engineering)
2. Wagner, Norman J. (University of Delaware, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Jennifer N. Mills and Norman J. Wagner
Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716

Speaker / Presenter 
Mills, Jennifer N.

Keywords
experimental methods; colloids; construction materials; jammed systems

Text of Abstract
Geopolymers are an amorphous inorganic polymer produced via the alkaline-activation of clays, fly ash, and other aluminosilicate materials that are studied as a low-CO2 alternative to ordinary Portland cement (OPC). The structure of these binders forms as the result of a polycondensation reaction of reactive silicates and aluminates which dissolve from the aluminosilicate precursor in the alkaline solution. Differences in chemical composition and reaction kinetics between geopolymers and OPC necessitate measurements connecting chemistry, kinetics, and structure-property relationships of geopolymers for the design of these sustainable construction materials. Model aluminosilicate gel systems are studied to gain direct insight to the structure formation resulting from the polycondensation reaction. Modeling the kinetics of this structure formation as a function of chemical composition yields insight to the parallel structure formation in denser geopolymer binder systems. This work follows the development of the storage modulus of alkali-activated aluminosilicate gels to quantify the rheological extent of reaction of gels with variable aluminum concentration at fixed silicon and sodium concentrations. While the apparent gel time and equilibrium modulus depend on aluminum concentration, rescaling each dataset enables the creation of a master curve unifying the nucleation and growth kinetic mechanisms of gel formation, which is successfully fit to both an autocatalytic reaction model and an Avrami model. Preliminary measurements for the rheological development of alkaline-activated BP-1 lunar regolith simulant geopolymer binders indicate that denser systems follow a similar trend as the model gels. These results therefore provide key insights to structure formation and property development of geopolymers, crucial to design of sustainable construction materials.