CAREER: SusChEM: Controlling Carbonation Degradation in Sustainable Cements by Stabilizing Amorphous Calcium Carbonate

Princeton University, Princeton NJ

Investigators

Abstract

NON-TECHNICAL DESCRIPTION: Portland cement manufacturing accounts for 5-8% of global anthropogenic carbon dioxide emissions, and with concrete utilization set to double over the next few decades there is a pressing need for sustainable concrete alternatives. One such alternative is alkali-activated materials (AAMs), a class of cement whose manufacture emits less carbon dioxide than Portland cement. However, the long term durability of new cementitious materials must be understood and optimized prior to employment in the construction industry. This project investigates the chemical reactions that occur during degradation of AAMs due to exposure to atmospheric carbon dioxide, a form of degradation that plagues both Portland cement and new cementitious materials. The ability to arrest the degradation reaction(s) is being explored by exploiting the stabilizing effect of magnesium on the carbonate-based reaction products (amorphous calcium carbonate). The development of durable and sustainable cementitious materials will lead to the implementation of sustainable products in residential and commercial construction industry, which will significantly reduce the associated carbon dioxide emissions. The project promotes and encourages underrepresented minorities and women in science, technology, engineering and mathematics (STEM) through outreach components centered on the new applied science/engineering curriculum that is being instituted in high schools in New Jersey. TECHNICAL DETAILS: This project will provide a deep understanding of the complex phase formation processes that occur during carbonation-induced degradation of slag-based AAM pastes. Key objectives include (i) obtaining a fundamental understanding of the role of magnesium in stabilizing the precipitated amorphous carbonate phase and (ii) determining the short and long-term stability of the disordered phases, including calcium-(sodium)-alumino-silicate-hydrate gel and amorphous carbonates. Highly carbonation-resistant slag-based AAMs are being developed through this research, which have the potential to supplant existing cement technologies. To obtain this understanding a suite of state-of-the-art experimental techniques are being used, including training the next generation of scientists (undergraduate and graduate students) in cutting-edge research. Techniques include: micron-resolved atomic structural information obtained using X-ray pair distribution function analysis combined with micro-tomography, nanoscale elemental mapping using nano-fluorescence, X-ray diffraction, infrared spectroscopy, thermal analysis and synchrotron X-ray absorption fine structure.