Hydraulic lime is a general term for a variety of lime different from calcium oxide that sets by hydration, and consists of calcium silicate and calcium aluminate, compounds that can harden in contact
Smeaton's Eddystone Lighthouse. John Smeaton is credited with pioneering hydraulic lime in the 18th century, which led to the development of Portland cement and thus modern concrete. Painting by John Lynn.
Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid. It is the second-most-used substance, the most widely used building material, and the m
A single concrete block, as used for construction
Exterior of the Roman Pantheon, finished 128 AD, the largest unreinforced concrete dome in the world.
Interior of the Pantheon dome, seen from beneath. The concrete for the coffered dome was laid on moulds, mounted on temporary scaffolding.
Opus caementicium exposed in a characteristic Roman arch. In contrast to modern concrete structures, the concrete used in Roman buildings was usually covered with brick or stone.