Concrete is a widely used construction material, and for good reason. The material is very hard and sturdy, fire-resistant and enormously versatile. Concrete has a long lifespan, requires little maintenance and retains structural integrity for a long time. A disadvantage, however, is its high carbon footprint, but great solutions are being devised for that.
Traditional concrete has a rather high carbon footprint and CO2 emissions are particularly high during production. Fortunately, the concrete sector is not sitting still, which means that there is now also considerably more environmentally friendly concrete and a lot of work is being done on CO2-neutral concrete. So sustainable concrete, without loss of attractive properties such as quality and hardness. This makes 'the new concrete' a nice addition to bio-based building materials.
Making components more sustainable
Concrete traditionally consists of a handful of constituents; besides water, these are a binder such as cement and so-called aggregates (aggregates) such as gravel and sand. Possibly supplemented by some other admixtures or fillers. CO2 emissions can be drastically reduced especially by using a binding agent other than cement. Furthermore, there is much to be gained by recycling aggregates. By addressing both, CO2-neutral concrete is within reach.
To start with aggregate, where a new building is constructed, an old building is often demolished first. By separating and recycling the resulting waste, great strides can be made in circular construction: fewer new raw materials are needed and at the same time, the amount of construction waste that must be sent to landfill decreases. Consider concrete granulate recovered from concrete rubble.
Alternative ingredients
In addition to replacing aggregate such as sand and gravel with materials recovered from rubble and demolition waste, it is important to look closely at the binder. After all, cement in particular leaves a big mark on the carbon footprint. Such as the well-known Portland cement, cement that contains crushed Portland clinker. Hence the search for alternative binding agents. By replacing part or preferably all of the Portland clinker, more sustainable concrete can be created.
Take geopolymer concrete, in which residual products such as blast furnace slag (residues from the steel industry) and fly ash (from coal-fired power plants) are used in the binder. Curing here takes place with an alkaline liquid through a chemical process called geopolymerization, a different process from hydration as in Portland cement. Hence it is also called alkaline-activated concrete. Calcined clay can also be used as a partial substitute for Portland clinker in geopolymer concrete. Incidentally, blast furnace slag and fly ash have long been used in the Netherlands, giving our concrete a lower carbon footprint compared with many other countries.
It only works together
Developing and producing sustainable concrete, adapting the production process accordingly and actually deploying the new concrete. All in all, this is a radical transition that is only possible if it is taken up chain-wide. In other words, parties such as clients, builders, concrete producers and waste processors must cooperate in this. Consider the development and optimization of sustainable concrete mixtures that have virtually the same properties as traditional concrete. For which there is then also sufficient demand from the construction industry. After which a constant, stable supply of demolition and rubble waste, residual products (such as blast furnace slag and fly ash), or other components is needed.
Not for nothing did companies, industry associations, knowledge institutions and government agencies, among others, launch the Concrete Agreement signed. Together, the aim is to halve CO2 emissions by 2030 (compared to 1990) and to have all concrete completely CO2 neutral by 2050.
