It will probably be It will be several months before we know for sure what caused the catastrophic collapse of the Champlain Towers South building in Surfside, Florida last week, which killed at least 18 people. But it’s already clear that at least one culprit lacked concrete. In 2018, an engineering company warned that the concrete under the swimming pool and the entrance to the building showed “major structural damage” and found “abundant cracks” in the underground parking lot. Just a few months ago, the president of the building’s condominium association wrote that “Concrete deterioration is accelerating.
Although this kind of sudden and massive collapse of buildings is very rare, the problem of collapsing concrete is not at all. It is a slow crisis 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 generate staggering amounts of carbon emissions that fuel climate change.
Concrete, which is basically just sand and gravel glued together with cement, is by far the most widely used building material on earth. We pour enough of it every year to build a wall 88 feet high and 88 feet wide all around the equator. This is largely because the number and size of cities is exploding. The number of city dwellers has more than quadrupled since 1960 to over 4 billion, and it continues to increase. We add the equivalent of 10 New York City cities to the planet every year.
There is no way cities can grow so quickly without concrete. It’s an easy and almost magical way to quickly create relatively sturdy roads, bridges, dams, and sanitation housing for large numbers of people. It is estimated that 70 percent of the world’s population now lives in structures made at least in part of concrete.
But none of these structures will last forever. Concrete breaks and fractures in several ways. Heat, cold, chemicals, salt, and humidity all attack this seemingly solid man-made rock, working to weaken and break it from within. (Rising temperatures and atmospheric carbon levels should make things worst.)
This threatens not only high-rise buildings, but our concrete infrastructure. A 2021 report from the American Society of Civil Engineers found that over 20,000 concrete bridges across the United States are structurally deficient and almost half of the country’s public roads are in “bad” or “poor” condition.
Things are much worse in many developing countries, where building standards are low and regulations often ignored. To keep costs down, builders often use unwashed sea sand to make concrete. These grains are less expensive, but they are coated with salt which dangerously corrodes the rebar. Concrete buildings made from sea sand covered by dozens in the 2010 Haiti earthquake. Poor quality concrete was also probably one of the main reasons for a factory collapse in Bangladesh in 2013 which killed over 1,000 people. According to The Financial Times, as much as 30 percent Chinese cement is so low that it produces dangerously fragile structures called “tofu buildings”. Inexpensively manufactured concrete is one of the reasons why so many schools collapsed in the 2008 Sichuan earthquake in China, killing thousands.
This is all terrifying, considering that most of the concrete in the world has only been placed in the last few decades, and most of it in the developing world, China in the first place. China alone used more cement between 2011 and 2013 than the United States used throughout the 20th century. As a result, writes economist Vaclav Smil, “the post-2030 world will face an unprecedented burden of concrete deterioration… Future costs of material replacement will run into the trillions of dollars.
Digging out the billions of tons of sand and gravel needed to make all this concrete will inevitably damage countless riverbeds, lake bottoms and floodplains. Poorly regulated sand and gravel mining in many countries has wiped out large numbers of riparian fish and birds, damaged coral reefs and caused riverbanks to collapse. The industry has even spawned a criminal black market, riddled with corruption and violence.
As if all that weren’t enough, making all this concrete will have serious consequences for the environment. The cement industry produces 5 to 10 percent of global carbon dioxide emissions, behind only coal-fired power plants and automobiles as a source of greenhouse gases.