The most common type of cement in the world is Portland cement, which is made from limestone. Baked in a giant kiln at very high temperatures — think around 2,700 degrees Fahrenheit — limestone transforms into carbon dioxide and calcium oxide. That calcium oxide, or lime, is a key ingredient in the cement that holds our bridges, apartment buildings and roads together.
As a result, the cement industry generates 8 per cent of global carbon emissions — triple the emissions of the aviation industry.Article content Some producers are slowly trying to implement solutions. One option is simply making concrete with less cement. Hessam AzariJafari, the deputy director of the MIT Concrete Sustainability Hub, says producers can substitute fly ash – a product of coal combustion – or waste from steel production instead of limestone. These materials can also help bind concrete together without the need for copious amounts of Portland cement.
But progress is slow. Concrete is a crucial component in modern construction; changing its ingredients poses not only an engineering problem but also a regulatory and safety problem. When it comes to innovating in the concrete industry, “everybody wants to be third,” Toone said. In the United States, many individual states have their own specifications for how concrete should be made and with what materials; changing the ingredients of concrete will mean a painful regulatory overhaul.
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