Scoop with high-quality circular concrete at Contactweg Amsterdam

At a railroad underpass in Amsterdam, a partition consisting of seventy-five percent recycled concrete was installed Sept. 9. The secondary raw materials come from project Buiksloterham, elsewhere in Amsterdam. This is a pilot of the City of Amsterdam, ProRail and Heijmans. The cooperation is an important step towards a sustainable concrete chain.

Chantal Serree, Sustainability Advisor at ProRail: "Innovative materials and high-quality reuse are the building blocks of sustainable infrastructure. Material use is therefore also one of the four tracks of our Sustainability Roadmap. Concrete is one of our spearheads in this respect. This practical test provides valuable insights and experience that will help us to apply sustainable material use more and more often, and thus elevate it to a standard. Through our participation in the National Concrete Agreement, we are sharing these experiences with the entire concrete chain."

Concrete is known to be an environmentally polluting product. For now, much of the pollution is caused by the use of cement. By recovering and recycling cement, much of the environmental burden is saved. New separation techniques from concrete supplier Rutte Groep make it possible to recover the original raw materials of concrete -sand, gravel and cement. From these loose products, a concrete mixture is then remade. With secondary cement i.c.m. recycled sand and gravel, the project at the Contactweg has a first. Never before has such a high percentage of recycled, reinforced concrete been used. As a result, this project is expected to save 27% of CO2 emissions and 26% of EQI (environmental cost indicator).

"A conscious decision was made not to use concrete granulate," Marc Ottelé says. He is a consultant on materials and technology at Heijmans. "By using high-quality recycled raw materials instead," Ottelé continues his story, "we achieve a much higher replacement rate for both sand and gravel, without decreasing the quality and constructive capabilities of the product. In other words, the functional performance requirements are maintained." Finally, Ottelé indicates that traditional reinforcement was chosen for the reinforcement instead of alternative reinforcement products. We do take this seriously, but we do not yet want to combine these influences with the changing of other raw materials for the simple reason that too little is known about their influence on both the durability and the structural safety of the construction.

This project used concrete composed of one hundred percent recycled gravel, fifty percent recycled sand and fifteen percent recycled cement. This leads to a secondary composition of seventy-five percent. Over the next five years, Heijmans will monitor how the circular concrete behaves during different weather conditions.

Adrie van der Burgt, Sustainability Advisor at Heijmans: "Heijmans' ambition is to build completely circularly from 2023. Central to this is limiting primary raw materials and reuse. To achieve this, we need to work together with our clients and partners and embrace new techniques. We are taking a big step towards a sustainable future and a healthy living environment with this sustainable concrete mix."