Construction company TBI and concrete producers Voorbij Prefab and VBI say they have found the solution to the high CO₂ emissions in the production of concrete. In their so-called NEXT level shell, with which four houses are now being built in Roosendaal, cement is largely replaced.
"For precast concrete, the biggest gain lies in cement reduction," says Niki Loonen, sustainable concrete consultant at TBI WOONlab. "By using less cement and using alternative binders, and adding materials that are CO₂ store, we can drastically reduce the impact of concrete."
According to the Concrete Agreement, the average CO₂ level of traditional concrete should be 204 kg CO₂ per m³. At Voorbij Prefab, they have lowered the concrete mixes step by step over the past few years and now produce at 115 kg CO₂ per m³ as standard. The concrete walls also incorporate biochar, which permanently stores CO₂ in the material. This reduces the impact even further.
Floors without cement
In fact, there is no cement at all in VBI's hollow-core slabs used within the serial housing construction. That reduces CO₂-impact of the houses even further. With that combination, the prefabricated casco arise with the lowest CO₂ footprint in the Netherlands.
"Ideally, I would have liked the entire casco to be made of cementless concrete," says Dick van Ginkel, technical innovation manager at TBI WOONlab. "But there are no standards for cement substitutes yet. These floors required a declaration of equivalence from the municipality." Gemeente Roosendaal was very cooperative on this issue, but making the homes entirely of cementless concrete was a bridge too far.
"The main premise was to show that innovation is possible," Van Ginkel continues. "As a sector, we need to act a step higher to reduce our CO₂-ambitions. By working together with different parties, we can actually realize that innovation."
Demonstration for future applications
The first application of the NEXT level casco is taking place in the Beekhof project in Roosendaal, where TBI construction company Hazenberg built the concrete cascoes for four homes. The project serves as a demonstration for future applications and shows how innovative solutions can actually be applied on the construction site.
