Cement factory near New Berrima, NSW, Australia
Believe it or not, cement contributes 5% of the world total carbon output every year – more than the entire aviation industry. So the invention of carbon neutral cement would go a long way towards helping reduce mankind’s carbon footprint.
Portland cement is made by heating limestone or clay to around 1,500°C. The energy used to generate this heat, and the decomposition of the limestone as it cooks, produces copious amounts of CO². In fact, for every ton of cement produced, 0.4 tonnes of carbon dioxide is contributed to the atmosphere. So with around 2 billion tonnes of cement being produced every year, the production of cement contributes 800 million tonnes of CO² into the atmosphere.
However, a professor at Sheffield Hallam University in the UK thinks that he has come up with the answer. Liquid Granite, Professor Pal Mangat claims, replaces the need for more than two-thirds of Portland cement when making concrete. “By the time we’ve finished with this developmental technology, the amount [of Portland cement] used will be close to zero” states Mangat.
Mangat is keeping tight-lipped about the exact formulation of Liquid Granite until he has finished the development of the product, although you wouldn’t blame him – by 2020 the French bank Credit Agricole estimates that demand for cement will be 50% greater than today, and a new carbon-free building material could reap incredibly huge rewards. All he will say at this point is that Liquid Granite is made from inorganic powder, 30-70% of which is recycled industrial waste materials. Using the same aggregates as normal concrete, it could be used in any of the same applications as Portland cement is – only with a fraction of the carbon footprint.
Professor Mangat said of the new product: “In some applications it is even more suitable than normal concrete. For example, one of the main areas we are currently exploiting it is fire-resistant building materials. It has good fire-resistant properties, unlike concrete, which explodes upon exposure to high temperatures.”
There has already been interest from the building industry, with Liquid Granite having already been used in fire-rated lintels at the Olympic Village and Stratford Shopping Centre in east London.
Professor Mangat is not alone in his development of carbon neutral cement. Last year Novacem, based in London, created a cement that has a negative carbon footprint over its lifetime. Their invention uses magnesium silicates, which emit no CO2 when heated, and the processing is carried out at a much lower temperature than that required for Portland cement. In addition, the cement actually absorbs CO2 as it hardens – it is claimed that each tonne could remove around 0.6 tonnes of the greenhouse gas over its lifetime.
