The path to low carbon concrete

Cement Works, Ipswich, Suffolk, UK.  (Photo by BuildPix / Construction Photography / Avalon / Getty Images)
Zoom in / Cement Works, Ipswich, Suffolk, UK. (Photo by BuildPix / Construction Photography / Avalon / Getty Images)

No one knows who did it first, or when. But by the second or third century BC, Roman engineers were routinely grinding burnt limestone and volcanic ash to make it. corn: A powder that begins to harden once it is mixed with water.

They made extensive use of still wet clay as a mortar for their stone and brickwork. But they also learned the value of stirring in pumice, pebbles, or pot shards along with the water: Get the proportions right, and the cement will eventually bind it all into a strong, durable, rock-like conglomerate called opus caementicium or – in a later term derived from a Latin verb meaning “to collect” –concrete.

The Romans used these marvels throughout their empire—in bridges, breakwaters, the amphitheater, and even temples like the Pantheon, which still stands in the center of Rome and still boasts the largest unreinforced concrete dome in the world.

Two millennia later, we did the same thing, pouring concrete with gigatons for roads, bridges, tall buildings, and all the other large parts of modern civilization. Globally, in fact, mankind now uses an estimated 30 billion metric tons of concrete annually—more than any other material except water. And with fast-growing countries like China and India continuing their decades-old building boom, that number is only set to go up.

Unfortunately, it also added our longstanding love of concrete Our climate problem. diversity corn It is most commonly used to bind concrete today, a 19th-century innovation known as Portland cement, and made in energy-intensive kilns that produce more than half a ton of cement. Carbon Dioxide per ton of product. Multiply that by global utilization rates in gigatonnes, and it turns out that the cement industry contributes about 8 percent of total carbon dioxide2 emissions.

True, that’s nowhere near the parts attributed to transportation or energy production, both of which are over 20 percent. But as the urgency to address climate change increases public scrutiny of cement emissions, combined with potential government regulatory pressures in both the United States and Europe, they are becoming too great to ignore. “Now we’ve realized that we need to get net global emissions to zero by 2050,” says Robbie Andrew, a senior researcher at the CICERO Center for International Climate Research in Oslo, Norway. “And the concrete industry doesn’t want to be the bad guy, so it’s looking for solutions.”

Major industry groups such as London based World Association of Cement and Concrete Based in Illinois Portland Cement Association They have now released detailed roadmaps to bring that 8 percent down to zero by 2050. Many of their strategies are based on emerging technologies; What’s more is expanding the range of underutilized alternative materials and practices that have been around for decades. All of this can be understood in terms of the three chemical reactions that characterize the life cycle of concrete: calcination, hydration, and carbonization.

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