In English | Issue 4/2021
Future binders for concrete
Changes in concrete binders will take place already in near future. Changes are boosted by the climate change. CO2-emissions of concrete are needed to reduce and thereby also the cements/binders need modifications. Portland cement has a long and successful history, but new alternatives are inevitably coming to Portland cement. In this article the probable future changes of concrete binders are estimated. Also timetable for the changes is forecast.
There is not a single solution for reduction CO2-emissions of concrete, but different approaches will be needed. The possibilities to reduce CO2-emissions of binders can be grouped into three methods:
- Large-scale use of blended cements
- Use of alternative binders
- Low carbon manufacturing process of Portland cement
More intensive use of blended cements, for example CEM III type cements, is considered as the fastest and easiest method for reduce CO2-emissions of concrete. The European standards allow high amount of secondary cementitious materials in concrete. Also, blended cements have been used for a long time in concrete manufacturing with good experiences. However, blended cements with high slag content will change the properties of concrete, especially the strength development is delayed and also the durability properties may change. In future, the availability of blast furnace slag can be a challenge.
Alternative binders are developed actively. Alternative binders do not contain Portland cement and therefore enable rather low CO2-emissions. There are several different types of alternative binders and the most common are alkali-activated binders and geopolymers. Alternative binders can be manufactured from different side materials of industry and also from some waste materials. However, the availability of raw materials is rather limited and therefore also the use of alternative binders will probably stay on rather low level. In addition, alternative binders are not fulfilling the requirements of the European standards, and this will restrict the use in the load-bearing structures.
The final solution for reducing CO2-emission of cement/concrete will be the low carbon production of Portland cement. Large investments are needed for capturing the CO2 from the clinker production process. Also, the calcination process can be carried out using electricity instead of fossil energy. CO2-emissions pf cement production can be radically reduced, and availability of raw materials will not cause such problems as with other methods.
Based on the estimations, the use of blended cements will increase significantly in near future. Also, alternative binders will be used more, but their share will remain on low level because of the limited availability of the raw materials and restrictions to use them in the load-bearing structures. It is estimated that the CO2-emissions of Portland cement production can be significantly reduced in 10 years. This will make concrete as carbon neutral material and even carbon negative material when the carbonation of concrete is taken into account.