An enzymatic self-healing cementitious material

Concrete is the most widely used material in the world and is responsible for 8% of global carbon emissions. It is inherently brittle, and it requires frequent repair or replacement, which are expensive and generate large volumes of CO2. Current methods of repair by agents such as mortar and epoxies result in structures with reduced strength and resiliency due to material mismatch, therefore, a self-healing cement paste (concrete’s main matrix) is needed to overcome this problem. The leading self-healing mechanism is based on the use of bacteria and microbes, which are slow and have limited applications, as well as unknown health effects. Inspired by the extremely efficient process of CO2 transfer in biological cells, this study introduces a method to develop a self-healing mechanism in a cementitious matrix using trace amounts of the enzyme Carbonic Anhydrase (CA). CA catalyzes the reaction between Ca2+ ions and atmospheric CO2 to create calcium carbonate crystals with similar thermomechanical properties as the cementitious matrix. The crystal growth rate using this method is orders of magnitude faster and more efficient than bacterial methods, resulting in the healing of large flaws on timescale orders of magnitude shorter. This method is capable of self-healing samples with millimeter-scale flaws within 24-hours and is significantly faster than all current methods that need a minimum of 28-days for strength recovery of microscale cracks. This inexpensive method is biologically safe, actively consumes CO2, and avoids using unhealthy reagents. It can be an efficient mechanism to repair and strengthen the existing concrete structures.