Boulder Dam on the Colorado river (Photo by Keystone-France/Gamma-Keystone via Getty Images)

Brute pleasures

Let us now praise famous concrete

Artillery Row

Concrete is safe, strong, inert, able to be cast in flexible shapes, fire and moisture resistant, cost effective, easy to maintain, pest free, durable. It makes the infrastructure that makes modern life possible — overpasses, tunnels, hydroelectric power, wind turbine foundations, sewage treatment facilities, airport runways, drainage pipes, railway sleepers, car parks, roads, highways, motorways, blocks of flats, office buildings, pavements, foundations, seawalls, jetties, breakwaters, sewers.

When reinforced with steel, it makes buildings earthquake resistant. It holds back mighty rivers and prevents destructive flooding. It stops storm tides from destroying towns. It makes roads safer to use. It is insulating and energy efficient. It makes good sound insulation. Concrete has grandeur, too. It has given the world the Hoover Dam, the Pantheon dome, the Pentagon, London Bridge, the statue of Christ the Redeemer in Rio de Janeiro, the Panama Canal. 

Without concrete, we would not have the architecture of Frank Lloyd Wright: the continuous spiral ramp of the Gugenheim, the cantilevered balconies of Fallingwater, the cathedral-like columns (inspired by trees) of the Johnson Wax Company — all reliant on concrete to make them feasible. With concrete, Wright produces some of his most imaginative work like the futuristic, circular Annunciation Greek Orthodox Church. Wright often relied on a then-new type of concrete — steel reinforced concrete. Concrete is resistant to stress but susceptible to cracking under the wrong sort of tension. When reinforced with steel it becomes much stronger and less likely to buckle when it bends. 

Self-healing concrete contains bacteria that react with water to produce limestone

Steel reinforced concrete fails slowly — as seen in some of Wright’s buildings, it sags before it collapses. This is a huge safety improvement over unreinforced concrete. It is this that makes so many modern uses of concrete possible. The steel inside concrete naturally corrodes, leading to decay and relatively short lifespan of modern concrete compared to Roman concrete. As the Construction Physics blog has pointed out, this is less of a problem than it looks: it is expensive to reinforce concrete more than we usually do and most buildings get pulled down for other reasons long before they would reach any extended lifespan that additional reinforcement would give them. Modern concrete has traded longevity for safety and much wider application, making modern construction possible. 

Concrete can also be reinforced with glass, natural and synthetic fibres, and polypropylene. Reinforcement allows concrete to withstand shocks and to be made into longer, thinner shapes. It is this reinforcement that allows us to put concrete to so many uses, to withstand the pressure of buildings, vehicles, tides and times. The long arcs of motorway bridges and slip roads, the tall columns that hold up bridges, foundation slabs — all unimaginable without reinforced concrete. It is reinforcement that makes concrete less likely to break in an earthquake, giving people time to escape.

Some people want to move away from concrete and use timber, but this would require tripling the amount of timber harvested every year. The majority of the world’s concrete is used in China, and, as nations like India develop, concrete use will increase. The latest innovation in concrete is to produce it without traditional cement. Cement is what makes concrete environmentally unfriendly, accounting for some 10 per cent of the world’s carbon emissions. Industrial by-product materials like coal ash and furnace slag can be treated with alkalines to make them bind like cement. This provides a use for industrial waste and reduces the need to produce Portland cement. It is also possible to use materials like crushed bricks, plastic waste and scrap tyres. This is not an easy catch-all solution, but other innovations reduce emissions, such as green energy in production and carbon capture at the manufacturing stage

One of the advantages of traditional Roman concrete over modern reinforced concrete is longevity — the Pantheon is still here but modern buildings don’t have anything like that lifespan. Self-healing concrete is being developed, which contains bacteria that react with water and oxygen to multiply and produce limestone, thus filling any cracks that appear and increasing the lifespan of the building. Another form of self-healing concrete was recently used to repair a failing water tower in Malta. This form of concrete seems to be recyclable as well, thus extending the promise of concrete infrastructure to be sustainable and environmentally friendly.

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