As Congress navigates another last-minute scramble to approve funding for the nation’s highways ahead of a July 31 deadline, engineers far-removed from the Capitol Hill gridlock are hard at work improving the stuff that sustains our nation’s roads and bridges: concrete. Technology exists for self-healing concrete, an auto-mending material containing limestone-producing bacteria that activates when wet. The bacteria can lie dormant for up to 200 years, according to the European Patent Office, where the technology is registered.