The cement industry is one of the largest industrial emitters of greenhouse gases. Denmark’s Aalborg Portland, part of the international Cementir Group, is gearing up to bring a new type of cement to the market, which could cut the industry’s emissions by up to 30%. The product is expected to be commercial by the end of 2020

Cement, used to make concrete, involves decomposing limestone (calcium carbonate) to produce clinker, a process that accounts for two-thirds of the industry’s carbon dioxide (CO2) emissions. Reducing the clinker content of cement is a key climate lever. Calcined clay has for some time been hailed as a potential replacement for clinker. Denmark’s Aalborg Portland, a producer of cement, says it will have cement made from calcined clay commercially available by 2020.

The cement industry is the third-largest industrial energy consumer in the world and the second-largest industrial emitter of carbon dioxide, responsible for about 7% of global CO2 emissions, says the International Energy Agency. As the global population rises and urbanisation grows, the agency forecasts an increase in cement production of 12% to 23% by 2050.

“We have developed the technology needed to produce the cement of the future,” says Michael Lundgaard Thomsen, CEO at Aalborg Portland. “The combination of calcined clay, limestone filler and cement clinker may reduce the consumption of traditional cement clinker by up to 30% and has the potential to reduce CO2 emissions by 30%,” says Lars Thrane, project manager at the Danish Technological Institute, which has optimised and tested the technology.

Thrane sees potential for the new cement globally, to reduce emissions and solve related challenges facing the industry. The traditional use of fly ash from coal-fired power plants will become problematic as coal is phased out. “Fly ash has been widely used in the concrete industry with good results as it has helped keep down CO2 emissions. But when fly ash disappears, we must find an alternative and this technology is by far one of the best bids,” says Thrane. The fact it uses clay, a raw material available in vast quantities everywhere, is another advantage.

Testing, testing

The green cement has been tested and documented in laboratory conditions and is being tested at four demonstration sites across Denmark, three motorway bridges with moderate traffic and in a concrete floor and wall in a new laboratory at the Technical University of Denmark, a partner in the project. Preliminary laboratory results show the green concrete is fairly similar in quality to traditional concrete. “We have looked at a number of applications, both large constructions in aggressive environments such as bridges and ports, but also buildings,” says Thrane.

In addition, large blocks of concrete, made from different compositions of the cement, are being trialled in two ports, Rødby, in the most southern part of Denmark, and Hirtshals, in the most northern part of the country, to see how the cement reacts to sea salt. “There are significant differences between the two ports in terms of seawater concentration, especially the content of chlorides,” says Thrane.“Hirtshals probably represents some of the most extreme exposure conditions concrete can be subjected to in terms of wind and weather.”

The concrete blocks have been lowered halfway into the sea to examine the splash-zone, the area moving in and out of the water due to waves and tidal water. “The splash-zone is one of the most vulnerable parts of a concrete structure, partly due to salt from the sea and partly because of oxygen from the air,” says Thrane. In Hirtshals, surveillance equipment has been installed so live data can be monitored to detect signs of corrosion such as the formation of rust.

“As soon as we see signs of something happening, we raise the blocks and take out core samples to examine the chloride ion concentration,” he continues. “The chloride threshold value — how much chloride is needed under given conditions to initiate corrosion — is a decisive factor when determining the service life of a concrete construction,” says Thrane. Large infrastructure projects are typically designed to have a lifespan of around 120 years, he adds. The concrete blocks were examined before being lowered into the water. A year later, core samples were taken to see how far into the concrete the salt had penetrated.

Eight concrete blocks, also fitted with surveillance equipment, are likewise in place on one of Denmark’s busiest roads near Copenhagen to test how the cement reacts to road salt in winter. Winters in the country’s capital can be hard, with weeks, sometimes months, of ice and snow.

“The great thing with these exposure sites is that there are no risks, so we have been able to make cement compositions with higher amounts of clay than at the demo-sites,” says Thrane.

Pricing and costs

The final steps to commercialisation include getting paperwork in order and field testing the technology. The company is selecting customers for field tests, which will initially focus on ready-mix concrete used in on-site castings such as foundations.

Interest in testing the cement is substantial, but it is too early to determine the real sales potential. One decisive factor will clearly be price. “We have not yet determined a price, but it will not be cheaper than the cement types we sell today,” says Lundgaard Thomsen. “The materials are more expensive, but the final price will depend on a number of factors, demand, availability of raw materials and, not least, how fast the new cement will replace existing cement types.”

He acknowledges it is likely to take some time before the green cement catches on, but expects it to corner a significant part of the market in the longer term. “The cement sector is characterised by knowledge of durability and safety and my guess is that customers will want to take their time before replacing their usual type of cement with a new product,” say Lundgaard Thomsen. “They will want to be sure there are no quality issues and that everything has been tested before massively entering this new market.”

The cement was developed in a four-year research and development project supported by the Danish Innovation Fund with a total budget of DKK 29 million (€3.9 million). Large investments will be needed in the future too, says Lundgaard Thomsen. “If the green cement ends up with the same amount of demand as other types of cement, we are looking at three-digit million amounts in investment for new production processes.” New types of machinery will be needed such as new rotary kilns used to raise materials to high temperatures. Aalborg Portland will carry the investment, he adds.

Other green cement technologies are being developed around the world, some similar to Aalborg Portland’s, but the mix of calcined clay and limestone filler with cement clinker is unique, insists the company. “The way we mix the ingredients is patented by us and the patent runs for ten years,” says Lundgaard Thomsen.

This article was originally posted in FORESIGHT’s technology section




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