In 2023, researchers at MIT and Harvard showed that ordinary cement, water, and a small amount of carbon black can be combined into a material that stores electricity, not in a battery embedded in the structure, but in the hardened concrete itself. As the cement hydrates, it consumes water and leaves a network of fine pores behind. The hydrophobic carbon black migrates into these spaces and self-assembles into a percolating, fractal-like electron-conducting network threaded through the calcium-silicate-hydrate (C-S-H) matrix. Soaked in an electrolyte and paired across a thin separator, two such electrodes form an electric double-layer capacitor, a supercapacitor, that stores charge electrostatically across an enormous internal surface area. The more interfacial surface inside the block, the more charge it holds. By the researchers’ calculation, a foundation-scale block of roughly 45 cubic metres, a cube about 3.5 metres across, could store on the order of 10 kilowatt-hours, comparable to a household’s average daily electricity use, while still bearing structural load. A 2025 follow-up reported a roughly tenfold increase in energy density, shrinking the volume needed for the same storage. This remains laboratory-scale work, demonstrated so far in small cells and prototypes, not a deployed foundation. Open questions include cycle life, self-discharge, and real-world scaling. References Chanut, N., Stefaniuk, D., Weaver, J. C., Zhu, Y., Shao-Horn, Y., Masic, A., & Ulm, F.-J. (2023). Carbon–cement supercapacitors as a scalable bulk energy storage solution. Proceedings of the National Academy of Sciences, 120(32), e2304318120. Stefaniuk, D., Weaver, J. C., Ulm, F.-J., & Masic, A. (2025). High energy density carbon–cement supercapacitors for architectural energy storage. Proceedings of the National Academy of Sciences, 122(40), e2511912122. PHENOMICA — contemplative, precise science, one phenomenon at a time. #science #materialscience #supercapacitor #energystorage #concrete …