Cementless clinkers

't Centrum is one of three realisations within the European URBCON project, which shows how 'greener' concrete can be made and used. Via technology partner ResourceFull 't Centrum came to Ebema for a more sustainable pavement around their building. "That was the moment for us to innovate with a low-cement version of the water-level clinker Halter Classic," says Frank Gendera. "In May 2023, we delivered 420 square metres of Halter Classics made mostly of cement-free geopolymer concrete. This type of concrete paving stone looks like an ordinary clinker, is just as strong and has the same colour and dimensions , but it contains much less cement."

Less CO2 emissions

"Cement is the classic binding agent for concrete, but it puts a burden on our environment. This is mainly because it is used so much worldwide," explains Livia Tasco, sustainability project manager at Ebema. "To produce one tonne of Portland cement also creates one tonne of CO2. This is partly due to the energy needed to heat the limestone - from which cement is made - but largely due to the CO2 in the limestone released during this process. When we make concrete with other binders, we can significantly reduce the most polluting ingredient. We calculate the carbon footprint of our products and include emissions from cement production. Our Life Cycle Analysis (LCA) by Ebema takes a much broader view and also takes into account, for example, the origin of our electricity. This allows us to calculate how much CO2 we emit per square metre of product. That gives us a good basis to work with."

For the Halters at Kamp C, we note 43% less CO2 emissions per square metre of paving compared to the Halter in cementitious concrete. On an area of 420 m², this means 3,507 kg less CO2 emissions. If you compare with a standard concrete paving stone that is not levelling, and thus has larger concrete mass, the sustainability gains become even greater.

Levelling and low-cement: a double ecological gain

Halter Classic is a level concrete paving stone from the Eco Solutions range. It has a wider joint for rainwater to infiltrate into the ground. The rainwater no longer flows away and can, for example, feed the groundwater supply. A form of smart paving. "Now that we can also make this levelling clinker in a low-cement version, we are making two advances for the environment," says Livia Tasco. "The right substrate and correct placement are important to get the most out of the water-level clinkers, though. That is why we bundle all the advice in our placement instructions."

Eco-concrete is not one type of concrete

"We investigated a lot of cement alternatives within the URBCON project," says Marijke Aerts, URBCON project manager. "Greener concrete is therefore a range of different types, depending on class, strength and available residual flows. For example, concrete with less cement or no cement at all, such as geopolymer concrete. But also concrete with recycled aggregates or even recycled concrete. The trick is to apply the right type of eco-concrete in the right place. And not to immediately resort to classic concrete as a building material."

A sustainable future in motion

"Ebema has been looking for alternatives for a number of years. That's why we work with good partners, such as ResourceFull. They optimise our concrete compositions. Geopolymer concrete can be part of the solution, although a concrete paving stone with cement remains cheaper at the moment. By the way, concrete with geopolymers is not new. In fact, it has been around for more than a thousand years, but is now becoming topical again. It is a good track in the switch to less environmentally damaging types of concrete. But in addition, we continue to look for other alternatives to deal more sustainably with our raw materials and our environment," concludes Frank Gendera, consulting engineer at Ebema.

"Today, so to speak, we use the same cement for a large bridge over a motorway as for the foundation of a post in our garden," continues Wouter Crijns, business manager of ResourceFull. "It is smarter to apply cement or alternatives based on the technical properties needed. And in doing so, to choose the most ecologically responsible option. Apart from alternative binders for concrete, there are other developments: concrete printing, CO2 capture and reprocessing in building products, alternatives to steel reinforcement, energy-efficient process techniques ... Less environmentally damaging construction techniques will not depend on one solution, but on a combination of different innovations. Reducing waste, smart reuse and CO2 reduction are important common denominators here."