As the article in the url below notes, concrete is very useful. It is also highly problematic:
"The most widely used construction material on the planet, it has given us sculptural buildings, sturdy bridges and dams, parking garages and countless other structures that surround us. But concrete is also responsible for about 8 percent of global carbon emissions. If concrete were a country, it would rank third in emissions behind China and the United States."
And, given how popular and versatile concrete is, this is not a small problem:
"In the United States alone, 370 million cubic yards of concrete was produced last year, with nearly 40 percent of it going into commercial real estate, according to the National Ready Mixed Concrete Association, a trade group."
This reminds me of a fact that I saw in the Financial Times a few years ago. While the U.S. uses a large amount of concrete, it pales into comparison when compared to its use in China, which "poured more concrete between 2010 and 2013 than the U.S. did in the entire 20th century." The cement industry knows this and is trying to do something about it. Who knew, but there is a lot of innovating going on in the cement industry:
"Before climate change became a pressing issue, concrete producers sought to reduce the amount of cement in their mixes for the simple reason that it tended to be expensive, in part because of the energy-intensive heating in producing it. Decades ago, they began substituting some of the cement with cheaper fly ash, a byproduct of coal-burning plants, and slag, a byproduct of steel production. Using such materials had the added benefit of diverting them from landfills, and they were also found to improve concrete's performance. Only in recent years has concrete with fly ash and slag been promoted as a greener product. But now there's a hitch: With coal plants being retired, fly ash is not as plentiful as it once was. The decline of steel production in some parts of the country has made slag scarcer. The shortages have set off price increases for these materials, adding to the urgency of experimentation with alternative concrete mixes."
Today, rather than cost on the supply side, the innovation is being driven by the demand side – i.e., architects and developers who are under pressure from their customers to producer more environmentally sustainable buildings:
"Recycled post-consumer glass — which otherwise might be sent to landfills — is being crushed into a powder, known as ground-glass pozzolan, that can be used in place of some of the cement in concrete. The cement industry is promoting Portland-limestone cement, which reduces carbon 10 percent, according to the Portland Cement Association, a trade group. Several new ways to make concrete greener employ waste carbon dioxide."
There are a number of examples detailed in the article, but this one from Canada illustrates the level of creativity currently re-shaping the concrete industry:
"CarbonCure Technologies, a company based in Halifax, Nova Scotia, invented a process that involves shooting liquid carbon dioxide into concrete during mixing. Doing so not only keeps the greenhouse gas out of the air but also strengthens the concrete and reduces the amount of cement needed. So far, CarbonCure concrete has a net carbon reduction of only 5 to 7 percent, but the technology has already been installed at 225 plants in the United States."
Take care
David
David Chandler
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A Fixture of Construction Gets a Lot Greener
By Jane Margolis
August 12, 2020
The New York Times
Late Edition – Final
B7
