First pouring of circular concrete in the Benelux

End-of-life WTC concrete used in Befimmo’s ZIN project

Friday, 11 June 2021, is the day of the first ever pouring of circular concrete in the Benelux. The upcycled rubble from the old WTC towers is being redeployed in Befimmo’s innovative, multifunctional ZIN project in the north district of Brussels. ZIN will replace the former WTC. To achieve this ingenious process Befimmo joined forces with De Meuter, ABR, CCB Concrete and the ‘Open Minds’ building consortium. It is worth noting that CCB Concrete is the first company in the Benelux, and only the second worldwide, to have obtained the international C2C Silver certification for its ready-to-pour concrete. In deciding to make circularity central in its ZIN project, Befimmo set itself a stiff challenge and now ranks as a pioneer in building a greener building sector.

30,000 tons of circular, C2C-certified concrete

“We at Befimmo are enormously proud that our ZIN project is the first ever project in the Benelux where circular, C2C-certified concrete is being used as a core component,” says Jean-Philip Vroninks, CEO of Befimmo. It certainly is a story without precedent: old concrete is put through a number of processes in a wharfage area not big enough to swing a cat in and, several months later, returns as a sparkling new, high-value product. “The impetus to go for such a degree of circularity came from the Flemish government and, resolved to accept the gage, we asked our construction partners to join with us in a quest to make the building sector greener,” continues Vroninks. At Befimmo’s instigation and in order to square this particular circle, CCB became the first Benelux company and only the second anywhere in the world to secure the Silver C2C certification. The partnership with CCB bodes well for other projects utilising circular concrete, with Befimmo able to deploy recycled aggregate in the manufacture of new concrete on other sites as well.

From old concrete to new in seven stages

30,000 tons of rubble was collected, sorted, ground and re-constituted into 3,500 tons of A+ aggregate. This high-quality aggregate was in turn incorporated into newly made concrete, giving 30,000 tons of new, C2C-certified concrete. This is the first time ever that this process has been deployed on such a scale in Belgium, for compression plating, floor plating and pre-fabricated plating applications. To achieve this, Befimmo joined forces with a number of other partners, each located no farther than a stipulated 15 km from the ZIN project site.

There were seven stages to the process:

stage 1: whilst dismantling the old WTC towers, De Meuter collected and sorted the resulting rubble from the ground plate and towers;
stage 2: the sorted rubble was hauled by lorry to the processing plant operated by All Belgian Recycling (ABR);
stage 3: the rubble was further ground down, graded and cleaned, giving ABR high-value A+ aggregate, which is stockpiled on concrete plating on its site before being hauled to its next destination;
stage 4: ABR hauls the A+ aggregate to CCB;
stage 5: around 30% of the mixture comprises recycled aggregate, earning it the Cradle to Cradle™️ Silver label. This carries an assurance that the concrete does not endanger the health of people or the environment and that it is recyclable. The certification entails that CCB is now furthermore bent on a process of optimisation, as the certification doesn’t only concern the product itself but it is also about embracing an entire philosophy;
stage 6: the newly made concrete is carried to the ZIN project site by cement-mixer lorries;
stage 7: Befimmo and the ‘Open Minds’ construction consortium (consisting of CFE, Van Laere, BPC and VMA) utilise the new concrete in the course of the reconstruction phase

seven stages to the process of circular concrete

Preserve, re-use, recycle

It isn’t simply the concrete that’s been upcycled. In total, 95% of the materials from the old WTC towers is being preserved, re-used or recycled, the prime example being the preservation of 65% of the old towers in the ground level, the foundations and the circulation cores. Over 1,000 tons of material will find a new life elsewhere. What cannot be preserved or re-used will go to recycling. Moreover, most of the new materials (95% of those used in the Flemish government’s offices) will be C2C-certified or equivalent.

ZIN is moreover designed with change in mind: it is adaptable and alterable to today’s needs as also tomorrow’s; each of its component parts (other than the floors and outer walls) can be dismantled with ease, meaning the base elements can be reused if needed without any great complication. The uniformly dimensioned outer walls are designed to accord with any type of use, be it residential, office or as an hotel.

“The ZIN project, and especially this new way of producing concrete, has positioned Befimmo as a pioneer in making the building sector greener. The fact of being a joint cooperation between private and public sectors is an important element in that. The Flemish government made a particular point of encouraging us to make these sustainability endeavours right from the dismantling stage, continuing through construction and to the project’s prospective commissioning,” says Jean-Philip Vroninks, Befimmo’s CEO.

“Both our ecological and our societal awareness are central strands in our decision-making – now and in the future. The Cradle to Cradle Silver certification earned under this project is evidence of our commitment and serves to give prominence to it,” adds Marie-Sophie Foucart, Concrete Operations Manager (Belgium and France).

“The real estate and construction industry is currently responsible for 40 % of global CO2 emissions. We are aware of this responsibility. Thanks to the recycling or circular approach, we can make our construction methods even more sustainable and efficient.” Raymund Trost, CEO CFE Contracting.

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