Probably it will be many months before we know for sure what caused the catastrophic collapse of the Champlain Towers South building in Surfside, Florida, last week, in which at least 18 people were killed. But it is already clear that at least one culprit has failed on the concrete. In 2018, an engineering firm warned that the concrete under the pool and the entrance to the building showed “great structural damage” and found “abundant cracks” in the underground garage. Just a few months ago, the president of the building’s building association “The deterioration of concrete is accelerating.”
Although such a sudden, wholesale collapse of buildings is very rare, the problem is collapsing concrete not at all. The slow-moving crisis is affecting much of the world. Billions of tons of concrete in the form of buildings, roads, bridges and dams may need to be replaced in the coming decades. It will cost billions of dollars – and create staggering amounts of carbon emissions that drive climate change.
Concrete, which is basically just sand and gravel glued together with cement, is by far the most commonly used building material on earth. Every year we pour enough to make a wall 88 feet high and 88 feet wide right around the equator. This is mainly because the number and size of cities are exploding. The number of urban residents has more than quadrupled since 1960 to more than 4 billion, and is still growing. Every year we add the equivalent of 10 New York cities to the planet.
There’s no way cities are growing so fast without concrete. It’s an almost magically inexpensive, easy way to quickly create roads, bridges, dams, and a relatively solid sanitary housing for a huge number of people. It is estimated that 70 percent of the world’s population today lives in structures made at least in part of concrete.
But none of these structures will last forever. Concrete collapses and cracks in dozens of ways. Heat, cold, chemicals, salt and moisture attack the seemingly solid artificial rock working to weaken it and break it from within. (Rising temperatures and atmospheric carbon levels are expected to create things worse.)
This threatens not only the apartment towers, but also our concrete infrastructure. A report by the American Society of Civil Engineers from 2021 established that more than 20,000 concrete bridges across the United States have structural deficiencies and almost half of the state’s public roads are in “poor” or “mediocre” condition.
Things are far worse in many developing countries, where building standards are low and regulations are often ignored. To reduce costs, builders often use unwashed sea sand to make concrete. These grains are cheaper, but are coated with salt that dangerously corrodes the armature. Concrete buildings made of sea sand packed dozens in the 2010 earthquake in Haiti. Bad concrete was also probably the key reason for the collapse of the factory in Bangladesh in 2013, which killed more than 1,000 people. According to Financial Times, as much as 30 percent Chinese cement is so low grade that it produces dangerous brittle structures known as “tofu buildings”. Cheaply made concrete is one of the reasons why so many schools collapsed in the Chinese earthquake in Sichuan in 2008, killing thousands of people.
All this is frightening, considering that most of the concrete in the world has been laid only in the last few decades, and most in developing countries – primarily in China. Only China used more cement between 2011 and 2013 than the United States did throughout the 20th century. As a result, writes economist Vaclav Smil, “The world after 2030 will face an unprecedented burden of concrete decay … The future cost of replacing materials will be in the billions of dollars.”
Excavating the billions of tons of sand and gravel needed to make all that concrete will inevitably damage countless riverbeds, lake bottoms and floodplains. Poorly regulated extraction of sand and gravel in many countries has wiped out huge numbers of fish and birds living in rivers, damaged coral reefs and caused the banks of rivers to collapse. The industry has even created a criminal black market, full of it corruption and violence.
As if all this is not enough, the production of all that concrete will hardly affect the environment. The cement industry produces 5 to 10 percent of the world’s carbon dioxide emissions, behind only fuel-fired power plants and cars, as a source of global warming gases.