't Centrum built with cementless foundations thanks to the Interreg NWE URBCON project

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Kamp C , the provincial Center for Sustainability and Innovation in Construction in Westerlo , recently took the first steps in the construction of 't Centrum on its site in Westerlo. This innovative building combines different pillars of sustainable construction to the first circular office building in Belgium: an innovative learning process from which the entire construction sector can draw inspiration.

Circularity and sustainability as a foundation

In circular construction, the principles of the circular economy are of course paramount. In essence, it is about materials being reused and recycled to the highest degree as possible with the highest possible value retention. In this regard , the concrete foundations are designed and dimensioned in such a way that they can be easily dismantled at the end of their useful life . For example, the dimensions are standardized and can therefore be used perfectly again in a new construction project in the future . This makes the foundations circular, but not necessarily sustainable. Traditional concrete contains a lot of cement, a raw material that is responsible for 8% of the global CO2 emissions every year. In order to go for a more sustainable solution, the builder called upon the low carbon footprint concrete mixtures developed in the context of the URBCON project.

URBCON reduces the use of primary raw materials and CO2 emissions

Concrete is by far the most widely used building material in the world. The flip side of the coin is the enormous impact on our ecosystem. The cement industry in particular produces more than 4 billion tons of cementitious materials annually, responsible for more than 3 billion tons of CO2. Apart from this , tens of billions of tons of natural rocks and deposits are also excavated every year for use as sand or aggregate. The URBCON project subsidized by Interreg NWE combines leading-edge knowledge and know-how in sustainable concrete to tackle exactly these issues . URBCON optimizes the use of industrial by-products such as metallurgical slags or industrial ashes to produce circular, durable and high quality concrete.

From sample in the lab to 55 m³ foundation blocks in the ground

Led by ResourceFull and with the support of UGent a suitable concrete mixture was developed for the foundations' t Centrum with the least possible environmental impact. The research started with the development of sustainable binders based on industrial waste streams. Traditional cement reacts with water, after which it hardens and develops strength . Water alone is not sufficient to start the reaction of these industrial residual flows. To initiate the reaction mechanism, the addition of chemical activators is necessary. That is why the team worked hard in the lab on the right combination of raw materials and chemical activators and additives. At the mortar level, properties such as tensile and compressive strength, flow and shrinkage were examined. In the concrete labs , the mixtures were upscaled based on the material and concrete properties of the intended application. The granular skeleton was designed with an in-house developed granular packing model optimized on the basis of the available sands and aggregates at the producer. Based on the tests on fresh concrete (flow, flow stability , curing time), on cured samples (compressive strength, shrinkage, density, E-modulus) and on durability (freeze-thaw, resistance to carbonation , chloride penetration) equivalence with the two traditional blends : (i) C20/25 EE2 S5 and ( 2 ) C30/37 EE3 ZVB.

Strength measurment on mortar beam

Upscaling to concrete level

Preparation of concrete samples

The production of the foundation blocks was carried out by Willy Naessens Construct in  Oudenaarde. Since the raw materials are readily available in the production silos, the implementation of the developed low carbon binders was limited to the adaptation of the programmed mixing ratios, and the manual dosing of the ResourceFull activators (15 to 40 kg / m³). The mixtures had a flow stability of 60 minutes, which is more than sufficient in a prefab production environment. After a final quality check, all foundation elements were approved and successfully installed by Beneens in Westerlo. As icing on the cake, another 6 m³ of fresh eco-concrete was delivered from the ready-mix concrete plant J. Janssens & Zonen in St.-Lenaarts. By using the URBCON concrete compositions in these foundation blocks, 22 500 kg of secondary raw materials could be used and 13 000 kg of CO2 emissions have been saved compared to using traditional foundations.

ResourceFull activators and additives

Highly flowable

Foundation blocks without cement

Ready-mix low carbon concrete