The construction industry took real action regarding low-carbon construction only a few years ago, at least judging by the demand for low-carbon construction products. The sudden rise in demand also got the concrete industry on the move regarding low carbon.
Low-carbon concrete construction is based on low-carbon cement, where a significant part of the clinker has been replaced with low-emission blast furnace slag. Low carbon based on blast furnace slag is a safe solution because slag has been used in concrete for decades. The technology is therefore tried and tested, the behavior and properties of low-carbon concrete are well known, and there are no unknown "newness risks" associated with the material.
With the introduction of low-carbon binders, the industry has rapidly brought to market a whole range of low-carbon concrete construction products, from hollow core tiles and other elements to paving stones, and everything in between. Of course, low-carbon ready-mixed concrete has been on the market for more than 10 years.
The carbon footprint of new low-carbon concrete construction products is significantly lower than before, typically around half of the original level. The change is significant, as the lowest-carbon apartment buildings on the market will be built from concrete in the future.
Low-carbon concrete elements are a clear solution for the builder, because the hardened concrete products are completely equivalent to traditional products in their other properties. Instead, the contractor pouring with low-carbon ready-mixed concrete should be aware of the concrete's slower strength development, especially in cool weather. Low-carbon site castings must be carefully planned and during construction, preparations must be made to protect the castings and possibly also to heat them.
However, blast furnace slag is only an intermediate solution. As steel manufacturing becomes low-carbon starting in the 2030s, the manufacturing process will hardly produce slag suitable as an admixture for cement. However, this does not pose a problem, as it can be seen that the cement industry smoothly transitions from the use of slag to the recovery of carbon dioxide. Thanks to this, conventional portland cement can be manufactured with very low emissions.
Carbon dioxide recovery is a well-known technology, but it requires large investments. Norway is already on the move. Carbon dioxide recovery is being introduced at a cement factory near Oslo. The purpose is that the carbon dioxide is stored in the drained oil pockets. We do not have this kind of storage facility in Finland. Instead, carbon dioxide has come to be harnessed as a "carrier" for green energy.
As Finland's wind power capacity increases to around 20.000 MW by the end of the decade, we will have several thousand megawatts of "extra" green electricity in windy times, which must be used. This is one of the reasons why the energy company St1 is planning a plant where carbon dioxide from the Lappeenranta cement plant is used to produce methanol. Methanol is much more suitable than electricity or hydrogen as a low-emission energy source of the future, for example in heavy and air traffic. Therefore, the cement industry will also be a significant part of the green energy system in the future.
Jussi Mattila
CEO, Betoniteollisuus ry
The article has been published On the Näkökulma section of Rakennuslehti 4.11.2022.
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