EAGER: Increased Service Life of Sustainable Cements via Electric Fields

Princeton University, Princeton NJ

Investigators

Abstract

This EArly-concept Grant for Exploratory Research (EAGER) project focuses on the modification of hardened cement internal structure via the application of electric field. Cement is a vital ingredient for the production of concrete, an irreplaceable construction material that is second only to water in terms of global usage. With population growth forecast to significantly increase over the coming decades and, with it, substantial urbanization, the world’s insatiable need for construction materials will continue. Thus, it is imperative that cement, which is currently responsible for 7% of anthropogenic CO2 emissions, undergoes rapid and drastic decarbonization to mitigate its effect on climate change. The use of more sustainable cements will significantly reduce these CO2 emissions; however, these cements also need to possess long service-lives and high levels of durability. This project addresses these needs via fundamental research aiming at using applied electric fields to deliberately change the atomic arrangements in sustainable cements prior to setting. It is envisioned that more crystalline cements will be more durable due to enhanced thermodynamic stability, elongating service-lives and thus providing additional CO2 savings in the concrete industry. This research will exploit electric fields to deliberately increase the thermodynamic stability of traditional and sustainable cements by enhancing the nanoscale ordering (i.e., degree of crystallinity) of their main binder gels. Given that the degree of crystallinity of a phase directly influences its thermodynamic stability, increasing the binder gel crystallinity will improve resistance to chemically-induced changes such as pH-induced decalcification. This will extend the service life of the concrete, and also has the potential to improve the physical and mechanical properties of the concrete. In this project, an electric field will be applied to silicate-activated flash calcined metakaolin, silicate-activated slag and ordinary Portland cement (OPC) paste, and its impact on reaction kinetics, mechanical properties and degree of crystallinity will be measured using a suite of experimental techniques that includes isothermal calorimetry, X-ray pair distribution function analysis and cryo-transmission electron microscopy (cryo-TEM). Moreover, to further enhance formation of crystalline binder phases the synergy between high dielectric constant dopant nanomaterials and electric fields will be explored, where the impact of (i) dopant morphology and (ii) dopant dielectric constant on the degree of crystallinity will be uncovered. Application of the electric field to these systems containing the high dielectric constant dopant nanoparticles should reduce the energy associated with electric-field-instigated crystal nucleation, and so too those containing anisotropic dopant nanoparticles, thereby further enhancing the formation of a crystalline binder. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.