Heard about the concrete catastrophe? Early last century, cement made up only 15 per cent of all global construction materials. By the 1970s, it was 60 per cent and still climbing. Almost all large buildings and many smaller ones are made of concrete, along with most public structures, all tunnels, airport runways, footpaths, bridges and many roads. It’s the second-most consumed substance on the planet – the only thing we use more of is water.
And every kilogram of cement produces half a kilogram of CO2. Concrete accounts for 8 per cent of the world’s greenhouse gas emissions.
This has now created another problem. While concrete is almost impossible to crush, it doesn’t easily hold together. For that, you need reinforcing steel (what Americans call rebar, or reinforcing bars). But concrete is permeable, which means CO2 gets in. This causes the rebar to rust, and when it rusts it expands, and when it expands it cracks the concrete.
This wasn’t a big problem for the first few decades of the post-war construction boom, but there is vastly more CO2 in the atmosphere now, in part because of concrete.
Reinforced concrete has an estimated lifespan of perhaps 100 years and already some structures are failing or showing clear signs they will soon fail. Concrete has begun to eat itself.
