A Portable and Rechargeable Method for the Complete Recycling of Concrete

Abstract

Concrete is the most widely used construction material in the world. Although concrete waste is mechanically ground and used as fill for construction projects, it cannot be recycled into components that can be reused for concrete structures and other purposes. This limitation is due to the inability to break cement bonds between the aggregates that form the intrinsic concrete structure. Here, we describe an electrochemical method to recycle concrete into its pure components, such as calcium carbonate, silicates, and metals (Al3+, Fe2/3+, Ca2+) through reactions initiated by sulfuric acid and by selective precipitation to gypsum, sodium silicate, clay, iron nanoparticles, and calcium carbonate. These components were assessed and quantified by analytical techniques. We show that concrete decomposition and purification of its components can be arranged in a stepwise cyclic process to yield a device that is portable, allowing on-site recycling. The process only requires a small amount of input energy. A main component of the process is a three-chambered electrodialysis system that regenerates both acid and base in situ, enabling closed-loop direct raw concrete processing rather than preprocessed powdered feedstock, making it a methodology that is both portable and rechargeable. Overall, our process allows us to completely break down concrete matrices to create input products for new structurally sound concrete, supporting a circular economy.