Netherlands Meet Sustainability Goals with Recycled Asphalt Paving
BY Hassan Tabatabaee and Susan Listberger
Sustainability is a way of life in the province of Friesland in northern Netherlands, including in its infrastructure. An important showpiece project for this region was the doubling of the provincial road N381 between Donkerbroek and Oosterwolde.
The work was awarded to construction company Heijmans, on the basis of its sustainable approach and circular high recycled asphalt pavement (RAP) ZOAB (porous asphalt) mixtures, made possible by incorporating a rejuvenator.
The N381 paving project is the latest example in circular road construction. In line with the sustainability objectives of the province, circular implementation is the guiding principle.
“It’s very stimulating, given our own sustainable ambitions at Heijmans,” said Gerbert van Bochove, innovation manager at Heijmans Infra. “We are happy when our clients recognize that we have the people, the knowledge and the technology to realize their plans together.”
The old surfaces of the road construction of this part of the N381 are recycled and processed in a circular two-layer porous pavement. Maximum circularity requires the reuse of the old layers.
This new approach guarantees the maximum achievable circularity for this project. In the field of circular porous pavements, Heijmans is building the showpiece in Friesland: a two-layer ZOAB with 60 percent recycled asphalt in the bottom layer and a top layer with 40 percent upcycled RAP.
“Recycling old porous asphalt is not as easy as it seems,” Van Bochove said. “The bitumen of porous pavement milling material is more oxidized and aged than that of SMA milling material, which has lost its necessary flexibility properties in the asphalt.”
As a result, it may lack the qualifications for the production of asphalt that meets the required technical specifications of a project. In that case, it becomes crucial to use an asphalt rejuvenator. Heijmans used a bio-based Anova rejuvenator from Cargill Bioindustrial to bring the chemical composition of aged bitumen back into balance.
“Heijmans has developed a special technique to produce a high RAP mix with the necessary properties using rejuvenation,” said Jan Struik, business development manager at Cargill Bioindustrial. “Heijmans conducted a great deal of research into the effect and functionality of rejuvenation products and their suppliers. Anova turned out to be very suitable for this purpose and thus making circular road construction possible. Besides the technical functionality, reliability of the supplier, cost per ton of asphalt and the sustainability profile played an important role in the consideration.”
On the N381 was an old two-layer porous pavement. These layers are now being reused in the circular mixes developed by Heijmans and validated by Rijkswaterstaat, which is the Directorate-General for Public Works and Water Management, for the new top layer.
“We have now gained a lot of experience with Anova, especially in bringing the bitumen to the desired specification,” van Bochove said. “We have already produced multiple high RAP mixtures in large volumes. The composition varies from 30 percent to more than 60 percent of old asphalt that has been brought to specification. We are increasingly working with circular asphalt with high percentages of reuse. By 2023, Heijmans wants to be able to process 100 percent circular asphalt on all projects.”
Heijmans is a listed company that combines activities related to property development, construction and technical services, and infrastructure. A constant focus on quality improvements, innovation and integrated solutions enables them to generate added value for their clients.
The Infra division focuses mainly on the construction, improvement, and maintenance of road infrastructure and public spaces in the Netherlands, including related installations and on-site objects. This could include roads, viaducts, tunnels, locks, water treatment plants, and work related to cables, pipelines and energy supply, but also technical work to make roads and public spaces safer, such as lighting, camera and referral systems are carried out by Heijmans Infra.
Hassan Tabatabaee is the global technical manager for Cargill Bioindustrial and Susan Listberger is the global product line manager for Cargill Bioindustrial. For more information, contact them through the Cargill website.