Paper Number
PO127 

Session
Poster Session

Title
Structure formation in alkali-activated binders for development of sustainable construction materials

Presentation Date and Time
October 23, 2019 (Wednesday) 6:30

Track / Room
Poster Session / Ballroom C on 4th floor

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)
3. Mondal, Paramita (University of Delaware, Civil and Environmental Engineering)

Author and Affiliation Lines (in printed abstract book)
Jennifer N. Mills¹, Norman J. Wagner¹, and Paramita Mondal^2
1Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716; ²Civil and Environmental Engineering, University of Delaware, Newark, DE 19716

Speaker / Presenter 
Mills, Jennifer N.

Text of Abstract
Cement production and use is one of the leading contributors to anthropogenic CO₂ emissions. Alkali-activated binders present opportunities for significant reduction in CO₂ emissions as well as in-situ resource utilization for lunar and Martian construction in support of human space exploration. The chemical composition of these types of binders has been shown to impact macroscopic properties such as workability and strength, but there is a lack of connection to the microstructure responsible or to the reaction mechanism of the ‘geopolymer’ hydration reaction and subsequent binder formation. Understanding the rheology development in such systems is crucial for applications ranging from traditional pumping, pouring, and setting as well as with the growing interest in 3D printing. Consequently, a mechanistic and quantitative understanding of the chemical kinetics and dynamics of microstructure formation and associated rheology development in model geopolymer binders will facilitate the universal engineering of construction materials from a variety of raw materials here on Earth, as well as those found on the surface of the moon and Mars.

The current work focuses on structural characterization of aluminosilicate gel hydrates with the objective of relating chemical composition to phase behavior. Gel formation kinetics are simulated through the dosing of the aluminum concentration in solution, the species which acts as the limiting reactant in the geopolymer binder, dissolving from aluminosilicate grains. Small amplitude oscillatory shear (SAOS) experiments characterize the microstructure development during transitions from liquid to gel. Complementary scattering data shows the microstructure responsible for this rheological behavior. A percolation threshold is identified at a relative concentration of 0.25 moles aluminum to 2 moles of silica and 1 mole of sodium in solution. These model system studies provide insight into the more complex rheological behavior of geopolymer cements.