When a tunnel segment of the Princess Margriet Tunnel rose due to upward groundwater pressure at the end of 2022, the urgency was immediately clear. Such an incident calls for action and speed. At that moment, there often seems to be little room to think about sustainability.
However, Klaas Braaksma, senior work preparer at contractor Van Hattum en Blankevoort, thought differently. He demonstrated that urgency and sustainability can go hand in hand if approached just a little differently.
New Foundation Piles
To be able to drill new foundation piles, Rijkswaterstaat and Van Hattum en Blankevoort removed the old concrete barrier of the tunnel. A section of about 100 m long and nearly 3 m wide. After the work was completed, a barrier had to be replaced to keep enough weight on the structure. The original solution? Pouring about 250 m3 of concrete again, resulting in a CO₂ impact of about 296 kg per m3.
‘It really felt like a waste,’ Braaksma says. ‘And then I thought: if anyone can bring about change here, its me. I have the connections with all parties. Why shouldn’t we do this differently?’
Sustainable Solution on the Worksite
Together with, among others, the concrete specialist and constructor, Braaksma explored alternatives. ‘That solution turned out to be surprisingly close,’ Braaksma continues. ‘Namely: LEGIO blocks. Large concrete blocks that were still on the worksite. In other words: leftover material that we previously used to temporarily stabilize the tunnel or that originated from leftover concrete after pouring work.’
These blocks turned out to be perfectly usable. Braaksma: ‘We combined the blocks with the planned concrete mix. Without compromising on quality, safety, or planning. But with results. We saved about 90 m3 of concrete, prevented waste and disposal by reusing leftover material, and thus achieved cost neutrality and environmental benefits.’
Thinking Differently
‘These kinds of solutions show that sustainability doesn’t have to be an investment,’ Braaksma concludes. ‘It mainly requires thinking differently.’ By making use of what already exists and looking just a little further than the standard solution, opportunities arise. Opportunities that may also inspire others.