Producing concrete has become a major source of global CO2 emissions. Simultaneously, 70 percent of the world's population is expected to live in cities by 2050. The growing need for infrastructure and housing means that the use of concrete will increase sharply. Therefore, there is an urgent need to find sustainable alternatives to traditional concrete. The industry understands the importance of this. According to RISE's concrete and materials experts, a new standard for recycled concrete could be introduced as early as 2025.
– It is already clear to some companies that traditional concrete sales will be difficult in just a few years' time. The big players are influencing the entire industry. There is a clear will among the country's cement and concrete producers, developers and building owners to move forward and reduce their carbon footprint. This is crucial for a real transition, says Jan Suchorzewski, unit manager for material design at RISE.
Alternative binders and the reuse of concrete elements are expected to be part of the solution in the future.
– There are a number of pieces to the puzzle that need to be put in place for reusing concrete to work in the marketplace, including technical safety in processes where we lack a standard in Sweden and the EU for ensuring the quality of reused concrete elements. There are methods developed in RISE research projects, but no current requirements. In addition, we need a link between demand and supply, i.e. a market place where we collect recycled building products for sale, explains Jan Suchorzewski.
There is a big difference between reusing products such as windows, doors, toilet seats and other construction-related products compared to load-bearing structures such as concrete frames in terms of requirements and safety.
– To ensure the quality of the material and its properties, such as strength, fire safety, sound insulation and so on, much more information and data is needed. But there is a lot of interest in both the construction and concrete industries. There are now several large-scale examples of successful projects from ambitious players, says Jan Suchorzewski.
We have started work on the development of a standard and quality assurance system for reusable precast concrete products.
Research with concrete results
A high-profile project has been carried out in Gothenburg, where RISE has been commissioned by NCC to reuse 3,000 square meters of hollow concrete slabs from the now-demolished Ikea store in Kållered. The hollow core slabs will now be part of a new housing development in another part of Gothenburg. This is after RISE has verified and tested the strength and life expectancy of the old concrete.
– When you have experience in this kind of mission, it goes pretty fast. That's also why we believe in standardizing to reuse. At Ikea, one of the things we did was research the technical documentation from when the store was built and compare it to the actual material. We re-examined the concrete and tested its compressive strength. It turned out that the concrete was of the same quality as when it was freshly produced and had the potential to last twice as long in the new buildings. That was fantastic, says Jan Suchorzewski.
A standard for recycled concrete is in the development stage. Hopefully as early as 2025. Jan Suchorzewski is a member of the Precast Concrete Committee at SIS, the Swedish Standards Institute.
– We have started work on the development of a standard and quality assurance system for reusable precast concrete products. There is a draft of the standard and we will be inviting the stakeholders in the industry to discuss it as early as the end of 2024. The hope is that a consultation will be sent out next year. The standard will be in place by the end of 2025, he says.
Alternative binders
An important part of concrete's future potential is recycling and reuse. Another is developing alternative binders to cement to make new concrete. Katarina Malaga, professor of sustainable construction with a doctorate in the chemical and mechanical degradation of stone and concrete, explains how this might be possible.
– Cement can be mixed with fly ash or slag. This is called climate-friendly concrete. However, there are technical requirements that limit the amount of alternative materials that can be used in concrete in order to have a quality guarantee. RISE is also working to develop and verify new alternative materials that have the potential to replace fly ash and slag, which are becoming less available as the power and steel industries transition. There are applications where we need to use a cement that will give us a robust and durable concrete structure that will last over 100 years, such as bridges and other infrastructure, she says.
Research, development and collaboration are the way forward
According to the two concrete experts: It's important to research and develop relevant, quality-assured solutions together with the industry.
One example is Betcrete 3.0, led by RISE with funding from Vinnova. This initiative brings together the entire value chain for the cement and concrete industry in a broad stakeholder collaboration. Another initiative is Återhus - building houses from houses, coordinated by RISE. 14 parties are involved, including Akademiska Hus, Heidelberg Materials, NCC, the City of Stockholm, Tyresö Municipality, Svensk Betong and others.
– Within Återhus we have, for example, the Lindome area development, which is managed by Förbo. The work includes the replacement of existing buildings with new ones. Here we will make an inventory of the buildings to be demolished and get a concrete picture of the current situation in terms of which load-bearing parts can be reused, says Jan Suchorzewski. This type of practical example will be useful for the entire industry, where we are pooling knowledge and experience.
Making innovations a reality
RISE has broad and deep expertise in concrete and cement. RISE has supported the Swedish concrete and construction industry with research, development, testing and education since the 1940s. The Nordic region's first large-scale test and demo environment for 3D printing of concrete was inaugurated in the spring of 2024.
– We provide an open platform for collaboration, development and learning. This accelerates innovation and ensures that things go from idea to reality. We can build prototypes, test them at full scale, and also develop everything from the material to the finished product, says Jan Suchorzewski.
Both he and Katarina Malaga are positive about the future and, above all, about the willingness of the various players in the industry, large and small, to embrace change.
– Many in the industry understand that climate concrete and circularity are the future if they want to survive, they conclude.
