Alkali-activated cements are low-CO2 alternatives to ordinary Portland cement-based concretes. These systems use aluminosilicate-rich earth materials (calcined clays such as metakaolin) or waste by-products (ground granulated blast furnace slag and/or coal-derived fly ash) as the main constituents and do not contain any OPC powder in mix designs. By alkali-activating the aluminosilicate and calcium precursors using hydroxide, silicate and/or carbonate-based activators, the resulting systems possess similar mechanical performance to OPC-based systems at a much reduced CO2 cost to the environment.
One of the main hurdles facing alkali-activated cements is the lack of long-term durability data. The Sustainable Concrete and Carbon Storage Group (SCCSG) at Princeton University is using advanced experimental and theoretical techniques to understand alkali-activated cements and subsequently to generate these crucial durability data.
Carbon Storage and Carbonate Materials
Carbon sequestration is an area of research to address the increasing amounts of CO2 being released into the atmosphere. One aspect of this technology involves injecting CO2 into depleted geological formations so that the CO2 molecules react with existing phases to form stable mineral compounds. Other technologies include sequestering CO2 above ground, such as via minerals carbonation. Therefore, understanding materials containing carbonate phases (various forms of CO3) is of relevance for carbon storage, together with the dissolution and formation mechanisms. Much remains unknown regarding the evolution of the atomic structure and nanoscale morphology of carbonate-based minerals in various environments (temperature and pressure). SCCSG is addressing these unknowns using a combination of advanced beamline techniques at synchrotron and neutron facilities together with ab initio and nano-scale theoretical methods. Furthermore, larger length-scale phenomena such as transport processes through the pores in geological formations (crustal conditions) at the micron level are also very important areas of research for this technology.