Most of us think of concrete as a modern material, and associate it with buildings constructed from the 20th century onward, but in fact it’s been around for a long time. So if you think concrete has no place in a period home, we aim to persuade you to think again.
Concrete is a material made up of aggregate (coarse particulate matter such as sand, gravel, rubble, and so on) bonded together by cement (which is fluid, but which sets and hardens over time). Amazingly, 8000 years ago, in the Middle East, the Nabataeans were using rubble and cement to construct buildings, floors and underground cisterns. But it was the Romans who made the greatest use of concrete in the ancient world.
Roman Concrete
The Romans made concrete by burning limestone to produce quicklime, to which they added water and volcanic ash, producing a durable mortar. This was combined with fist-sized chunks of brick or rock, and packed into place.
The resulting material allowed the Romans to build arches, vaults and domes more easily than with brick or stone. Some very impressive Roman concrete structures survive to this day, such as the Pont du Gard in Provence, and the Pantheon in Rome, with its enormous dome.
After the fall of the Roman Empire, the techniques for making concrete were forgotten for hundreds of years, but after the 1300s people gradually started using cement again.
Modern Concrete
In 1824, Joseph Aspdin burnt finely ground chalk and clay in a kiln to produce Portland cement. The same technique is used to this day to produce one of the basic ingredients of modern concrete.
Modern concrete differs from Roman concrete in two respects. Unlike Roman concrete, which was made by packing chunks of brick and rock with cement, modern concrete is made by mixing Portland cement, water and aggregate (rock, sand or gravel) to form a liquid mixture that can be poured into forms or moulds.
Secondly, almost all modern concrete is reinforced, usually with steel bars embedded in the substrate. On its own, concrete has good resistance to compression, but little tensile strength. The addition of steel reinforcement gives additional strength and allows not only the construction of very large high rise buildings, but also bold and striking curved structures, such as the roofs of the Sydney Opera House.
Aesthetic Considerations
Throughout much of its history, concrete has been thought of primarily as a structural material, often covered by a variety of finishes. The Romans covered their concrete in brick or marble, and in modern times, concrete has been plastered over and painted, or designed to resemble masonry.
However, in the twentieth century, some architects designed buildings where the concrete was left exposed, the contemporary version of the stone buildings of earlier periods, as it were. A variety of textured finishes were used, including allowing the concrete to set with the impression of the grain of the wooden moulds into which it had been poured. These uncompromisingly modern buildings—such as the South Bank Centre in South London–were not always popular, but as time has passed they are becoming more widely appreciated.
So if you’re in the process of renovating a property with a distinguished history, don’t be too surprised if you uncover concrete. It’s not the ugly, Johnny-come-lately upstart we often assume it to be, but a versatile material with a long and venerable past. No wonder many home-owners and interior architects are beginning to welcome it as an addition to their repertoire of heritage design resources.
