By trial and error to sustainable infrastructure

The desire of Rijkswaterstaat (RWS) to work completely climate-neutral and circular by 2030 is certainly ambitious. When constructing, replacing and renovating viaducts and bridges, the chain is currently not working in a sufficiently circular way. To accelerate the transition, RWS challenged companies a few years back with a Strategic Business Innovation Research (SBIR) call for tenders to develop solutions for circular viaducts. Of the original 32 entries, three remained in the final round to realize prototypes. Closing the Loop is one of them. This consortium of Nebest, GBN Groep, Antea Group and Strukton Civiel achieved a world first in March this year with the harvesting of girders from the Netherlands' busiest traffic artery in a DBFM billion-dollar project.

"High-quality reuse of artworks is a matter of chain cooperation, you don't do it alone," states Wouter van den Berg, Marketing & New Business Manager of Nebest. Together with Harry Hofman, Director of Circular Raw Materials at GBN Group, he initiated the consortium. "The ambition of Closing the Loop in our cooperation is to close the circle for high-quality reuse of bridges and viaducts. For this, Nebest inventories the reusability of existing engineering structures, deploying our own lab, inspectors and the reusability scan we developed ourselves. Antea designs new applications for the old parts, GBN takes care of the actual harvesting, dismantling and preparation of the materials, and Strukton realizes the new application. We also collaborate with a number of knowledge partners, including IMd Raadgevende Ingenieurs, NEN, Madaster, TNO and Gemeente Amsterdam."

The first concrete project is the reuse of concrete beams released during the widening and sunken construction of the A9 near Amstelveen. These will be reused in the construction of a new structure for the A76 near Nuth (Limburg), together with locally harvested beams. And riser plates, abutments and handrails, among other things, will also be reused. Hofman: "On March 16 was the very first harvest of 19 girders and on April 13 the second of 15. Now the big learning really begins. You do that by just getting started. We will definitely still encounter obstacles and setbacks, but we are going to overcome that. The problems are not so much technical, but are more in the area of working together in a complex environment. We are dealing with, in this case, construction consortium VeenIX that is taking care of the A9. This concerns ongoing contracts that were not concluded on sustainability ambitions. Together with RWS and VeenIX we managed to ensure that the girders could still be harvested. Normally the girders lapse to the contractor and end up somewhere via the crusher as foundation material." 

This actual harvest is preceded by several things. Van den Berg: "This begins with a reusability scan, in which the potential of engineering structures and their components is mapped out on the basis of existing information, damage reports, construction and fixing methods and previously conducted research by RWS, among other things. The next step within the reusability scan is a residual life analysis, which came out at over 100 years for the girders of the A9. GBN's harvesting plan should then ensure damage-free dismantling, including checks before, during and after. Veenix then created a work plan and harvested the girders."

The A9 beams are then cut to length for their new application and then go through a process of test loading. "This is because the girders are made without stirrup reinforcement, which deviates from existing laws and regulations. That need not be a problem, we have investigated together with experts from TU Delft, RWS and TNO, among others. Test loads are still useful to build in more certainties with regard to structural safety and for the development of standards. In a doctoral study we even want to demonstrate with TU that the structural potential is much higher than had been assumed."

The modification of the A9 alone will release more than 1,000 girders. Hofman: "The intention is to harvest as many girders as possible. You understand the task we face. Together with RWS and Liggers 2.0, one of the two other consortia from the last SBIR round, we are investigating how to harvest and matchmaking. RWS wants to use the A9 to further shape the scaling up of reuse of structures."

In cooperation, the key to success lies in achieving the ambitions that RWS but also BV Nederland has set for itself. Van den Berg: "In an ideal world, you already know where which usable structure parts are located and how to allocate them to other projects. That is the future. Currently we are trying to get a moving train on another track. We are putting an enormous amount of time and energy into optimizing the technical process and coordinating with RWS and VeenIX. And they also have to coordinate with each other. That is learning money that you have to bear collectively and from which we will later benefit collectively."