Cement as a Super-capacitor: Expanding the Functionalities of Hardened Cement Paste

More than 20 billion tons of concrete are produced every year, more than any other material on Earth, such that concrete production is responsible for about 10% of the whole anthropogenic production of CO2. Reducing CO2 emissions for concrete production, designing and optimizing material performances, resilience, and durability is hence crucial to sustainable growth and to meeting greenhouse gas emissions reduction goals.

 

Here we explore the possibility to expand the functionalities of hardened cement paste, which is the glue that provides strength to concrete. By adding carbon nanoparticles to the mix of cement powder and water, we demonstrate how hardened cement paste can be turned into an electrically conductive material without losing its mechanical strength. Such hybrid cementitious materials are promising candidates for designing structural super-capacitor that would allow the traditional walls of a household to serve as an energy storage device. In this talk, we will review the various steps involved in preparing a cement super-capacitor device. First, we will illustrate the rheological properties of aqueous dispersions of carbon nanoparticles and quantify the impact of the nanoparticles on the cement hydration process. Second, we will show that conductivity measurements on samples of hardened cement paste prepared with carbon nanoparticles allow us to identify a critical volume fraction in carbon nanoparticles above which the cement paste is electrically conductive and can, therefore, be used as an electrode whose mechanical properties will be quantified by nano- and micro-indentation. Finally, we will provide capacitance measurements of a cement super-capacitor prototype, confirming that the device is indeed a "super-capacitor" before emphasizing the key technical challenges that remain to be addressed for upscaling our project.