Understanding Early-Age Properties of Sustainable Concrete Binder

The concrete industry is facing a huge challenge to reduce its carbon footprint as cement production alone is responsible for 5-7% of overall anthropogenic carbon dioxide emissions. Alkali activated aluminosilicate gel, which is a class of semi-crystalline or amorphous 3D aluminosilicate (SiO2/Al2O3: 1-6) binders synthesized from alkaline activation of fly ash, metakaolin, and slag, is an immediate and reliable alternative to cement for reducing the CO2 emissions (by 80-90%) and has potential for immobilizing heavy metals or low level nuclear waste [1]. This material, often known as low-CO2 geopolymer cement, is a green, sustainable alternative to cement. However, due to limited understanding of the development of its nanostructure that directly influences the early age properties (i.e. rheology, setting, and shrinkage), as well as the final properties (i.e. strength, durability), control over such properties is inadequate. Earlier studies on elemental distribution (few atoms) or chemical environment of aluminum and silicon in alkali activated aluminosilicate gel provided useful information however, do not provide any information about the medium/long range order and morphological development [2-4].

Information regarding the structural development of alkali activated aluminosilicate gel is critically important in understanding the early age properties and developing admixture to control rheology, liquid to solid transition (setting), and autogenous shrinkage. Limited understanding and control over such properties is prohibiting the wide spread application of a potentially high impact sustainable alternative binder in the construction industry. We propose to investigate the formation of synthesized alkali activated aluminosilicate gel at early age using NMR, rheology, and scattering techniques to investigate the gel formation, and explore the effect of organic molecules on the structural development.

Furthermore, we are interested in the application of geopolymer binders for in-situ resource utilization (ISRU) for NASA’s ambition of human space exploration through Project Artemis. We are investigating the chemistry and kinetics of lunar and Martian regolith geopolymer binders for sustainable, low cost construction extra-terrestrial materials. This work is being supported by the Delaware Space Grant Consortium.

References

1. Van Deventer, J. S.J., Provis, J. L., Duxson, P., Technical and Commercial progress in the adoption of geopolymer cement, Minerals Engineering, 29 (2012) 89-104

2. Criado, M., Fernandez-Jimenez, A., Palomo, A., Sanz, J. S., Effect of SiO2/Na2O ratio on the alkali activation of fly ash. Part II: 29 Si MAS-NMR survey, Microporous and Mesoporous Materials, 109 (2008) 525-534

3. Bell, J. L., Sarin, P., Drimeyer, P. E., Haggerty, R. E., Chupas P.J., Kriven, W. M., X-ray pair distribution function analysis of a metakaolin-based, KAlSi2O6, 5.5H2O inorganic polymer (geopolymer), Journal of Materials Chemistry, 18 (2008) 5974-5981

4. White, C. E.,  Provis, J. L., Proffen, T.,  van  Deventer, J. S. J.,  The  effects  of  temperature  on  the  local  structure  of  metakaolin-based  geopolymer  binder:  a neutron  pair  distribution  function  investigation,  Journal of the American Ceramic  Society,  93  (2010) 3486–3492

Publications

1. Mills JN, Wagner NJ, Mondal P. Relating chemical composition, structure, and rheology in alkali‐activated aluminosilicate gels. J Am Ceram Soc. 2021;104(1):572–583. https://doi.org/10.1111/jace.17459

2. Mills J, Mondal P, Wagner N. Structure-property relationships and state behavior of alkali-activated aluminosilicate gels. Cem Concr Res. 2022;151:106618. https://doi.org/10.1016/j.cemconres.2021.106618

3. Mills JN, Katzarova M, Wagner NJ. Comparison of lunar and Martian regolith simulant-based geopolymer cements formed by alkali-activation for in-situ resource utilization. Adv Sp Res. 2021. https://doi.org/10.1016/j.asr.2021.10.045