HOLBÆK HAVE – CONSTRUCTION SITE 10

DAY-TO-DAY DELIVERY OF C20 ELEMENTS DRIVES CO₂ REDUCTION

Although it is not visible to the naked eye, Holbæk Have’s Building Plot 10 consists of something special — namely a considerable proportion of C20 concrete elements, where C35 concrete elements would previously have been used. This is made possible because CRH Concrete can now deliver C20 elements on a day-to-day basis at the same pace as other elements. This represents a unique and significant step forward in the use of CO₂-reduced concrete elements in construction.

The Holbæk Have district consists of a combination of owner-occupied and rental housing. Here, project developer FB Gruppen A/S and managing contractor Ingcon A/S have constructed 320 homes, which are already occupied, and they are now working on the blocks in Building Plot 10. CRH Concrete has supplied elements to all of FB Gruppen’s homes in Holbæk Have, and all concrete elements in passive environmental class — both C20 and C35 — are standard low carbon concrete (LCC) elements.

SUCCESS WITH DESIGN OPTIMISATION

— In connection with BF10 in Holbæk Have, we were involved in the design optimisation early in the project, and we therefore had time to develop new products together with our client. This is entirely unique to our collaboration with Ingcon. It has been a long time in the making, and there has been a great deal of testing to ensure that the concrete could be demoulded at the correct strengths, says Camilla Dyring, Head of Sustainability at CRH Concrete.

If the climate impact of a construction project is to be minimised, it requires all parties involved to invest time and effort in design optimisation from the very start of the project.

Illustration: The climate impact of the C20 elements has been reduced by 38% compared to our concrete elements in standard concrete C35, as we produced them a few years ago. However, we have also optimised our C35 elements in passive environmental class this year, and therefore the CO₂ reduction of the C20 elements is 21% compared to our standard LCC concrete elements in C35.

— To achieve the desired result, we worked closely with both our consultant and CRH Concrete from an early stage in the process to design-optimise the entire construction and reduce CO₂ emissions from this particular project, explains Jacob Bidstrup from Ingcon. Both FB Gruppen and Ingcon are focused on reducing their CO₂ footprint. At Ingcon, there is a dedication to continuously pursuing the next CO₂ reduction in construction projects.

— It is our overall objective to continuously reduce CO₂ consumption in our construction projects, and this has led us to the collaboration with CRH Concrete and our consultant regarding the C20 concrete elements. In connection with the design optimisation, it became apparent that there were several places in BF10 in Holbæk Have where we could reduce the strength requirements in the construction and did not need to use C35 concrete, but could make do with something less, says Jacob Bidstrup.

Hear Camilla Dyring (Head of Sustainability) and Dennis Mathiasen (Operations Director) talk about the use of C20 elements.

INNOVATIVE PRODUCTION AND DELIVERY

The quantity of C20 concrete elements required for the construction in Holbæk Have meant that CRH Concrete needed to be able to deliver elements every day in line with the progress of the construction. This placed new demands on production, and a great deal of calculation, testing and demoulding took place until the desired result was achieved.

— With day-to-day delivery of C20 concrete elements, we now have the opportunity to offer a different product where C35 elements would previously have been used in all walls. This also means that the CO₂ footprint of the construction becomes significantly different, says Camilla Dyring.

For Ingcon, it has been an instructive experience to be involved in the actual development of the elements.

— It has been very interesting to follow the material development and the challenges that arose, and to see how they were resolved. The actual delivery of the C20 concrete elements has also proceeded according to plan. They have arrived at the construction site at the agreed time. So CRH Concrete has completed the task to our full satisfaction, says Jacob Bidstrup.

HOLBÆK HAVE - BYGGE-FELT 10

CO₂ GAINS — NOW AND IN THE FUTURE

Work is currently under way on the project’s EPD. However, it is only once all C20 elements have been produced that it will be possible to see the specific concrete mix, the specific reinforcement level and obtain the precise figure for where the project lands in relation to CO₂ limit values. Nevertheless, it is already clear that the C20 elements result in a significant CO₂ reduction.

— When we produce C20 elements compared to ordinary traditional concrete walls in C35, we can reduce the cement content markedly. Specifically, the climate impact of the C20 elements has been reduced by 38% compared to our concrete elements in standard concrete C35, as we produced them a few years ago, says Camilla Dyring.

— However, we have also optimised our C35 elements in passive environmental class this year, and therefore the CO₂ reduction of the C20 elements today is 21% compared to our standard LCC concrete elements in C35, elaborates Camilla Dyring.

Day-to-day delivery of C20 elements is yet another important step towards reducing CO₂ emissions from concrete in construction. The same applies to the collaboration on design optimisation.

— In reality, it is about expanding our product catalogue so that we have different products on the shelf that can meet different functional requirements. That is how we optimise our products and achieve the lowest possible CO₂ emissions for the overall construction, concludes Camilla Dyring.

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Client: FB Gruppen
Managing contractor: Ingcon
Structural engineers: AFRY

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