Roman Concrete
Roman concrete was cool, but the new MIT result may be off-base
There was a story last month, Riddle solved: Why was Roman concrete so durable?, which attributed the longevity of the material to a self-healing form of lime. Cool story! But, as Brian Potter wrote in Construction Physics, the problem that the Romans were solving is not the problem that we solve for today. They solved for durability and strength in compression, but we use concrete quite differently, as steel-reinforced, which is a very nice building material with a different failure mode. Steel reinforced concrete fails because water gets in and degrades the steel, turning it (essentially) into rust-reinforced concrete. And as you may imagine, rust is not a particularly helpful reinforcement material.