Stone Was Made, Not Only Carved: The Rumour of Roman Concrete and Egyptian Pyramids

A pyramid block looks as if it was cut from a mountain, dragged through desert and placed high above the ground. That is the familiar story. Another story begins with a material nobody can deny: Roman concrete. Romans mixed lime, volcanic ash, water and stone fragments to make a material that could be poured into forms, used in domes and harbors, and survive seawater for thousands of years. When modern scientists cut ancient concrete samples, they do not see ordinary rock. They see chemical reactions, new minerals and lime fragments that react again when water enters a crack.