Buildings, regrettably, don't last forever. Until recently, the only way to increase a building's lifespan was ongoing maintenance, which can be expensive, time-consuming and in the case of infrastructure such as bridges or roads, inconvenient. Beyond that, periodic replacement of the entire structure was an option, however this is clearly not a sustainable solution, especially considering the amount of CO2-releasing concrete used in modern construction.
But in the 21st century, another alternative is emerging. This article on CityLab uncovers three self-healing materials that could significantly extend the lifespan of a construction, including Erik Schlangen's asphalt that re-sets itself with a dose of induction heating, concrete developed at TU Delft (and elsewhere) that patches up cracks with the help of its living bacterial aggregate, and a recent discovery by MIT scientists that some metals have self-healing properties.