Recently fellow member @TBA sent me a link reminding me about some new ideas in concrete technology I first heard about a year or so ago. Cracking, as you may suppose, is one of the biggest threats to the integrity of concrete structures. Water crystals freezing and thawing in a confined space of a crack can cause significant damage. Water can also deteriorate steel reinforcement, weakening critical parts of bridges, dams, etc…. Water and other chemicals and gasses can also make their way into a structure through micro-cracking, which is inherently present in concrete. The goal of “self healing” concrete is to figure out an additive to the mix that will repair cracks as they occur. Researchers have discovered a few kinds of ureolytic bacteria that can be mixed in the concrete when it is produced and lies dormant in the hardened concrete. If it is ever exposed to water through a crack however it will activate and produce limestone to fill the crack automatically. Here is a short video explaining the basics:
This is still in the research phase but there seems to have been significant progress made in the year or so since I first heard about it and could have tremendous impact on infrastructure projects like bridges, walls, damn and really any exterior concrete exposed to the elements.