The modern world has rediscovered how to build really tough concrete by using geopolymers, or concrete that does not need firing. Ancient Romans used the technique to build the Pantheon; Egyptians, the Pyramids. The US? Bunkers that resist all-but-nukes.
And runways that can support the full weight of the heaviest planes only hours after setting. The key process here is to add more alkaline activators to the mix, which helps concrete shrug off water and chemical wear. In ancient times, this meant mixing burnt lime with water and crushed stone. [Dangerroom]