RUBBER CONCRETE
Entrepreneur and innovator Johan Engdahl has always worked with concrete, having bought a mobile concrete plant at the age of just twenty. When people told him his plan wouldn’t work out, he simply replied: “But what if it does?” And it did. He still lives by the same motto today, which has led him beyond the purchase of a concrete plant to something bigger – and more unexpected: Rubber Concrete, a start-up business producing a brand new material made by using concrete and rubber from worn-out tyres.
The product consists of two materials that don’t normally go together, for the simple reason that one is a soft material and the other is hard. However, thanks to a combination of determination, patience and above all huge interest, Rubber Concrete has shown the value of following your instincts, even in the face of overwhelming odds.
Today, Johan runs Rubber Concrete together with Lars Roepstorff, a professor and veterinary surgeon at the Swedish University of Agricultural Sciences in Uppsala. His specialism as a world leader in horse riding surfaces means that Lars is often called upon to certify riding arenas. But how did it all begin?
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Rubber Concrete lectures at the annual event Däckbranschdagen / 10 maj, 2022
In 2020, Johan was commissioned to help his municipal equestrian school to build a new riding centre. When the time came to choose a material for the riding surface, Johan consulted ten people with varying degrees of horse riding expertise. To his surprise, he got ten different answers. He wondered whether this could really be true – surely there should only be one material? Johan contacted a professor at Chalmers University of Technology in Gothenburg, who turned out to be the project manager for the Chalmers jump at the Gothenburg Horse Show. After reading countless reports, he found that, rather than being any the wiser, he was only more hesitant about the best solution.
However, Johan noted that the same name cropped up time and time again in these reports: Professor Lars Roepstorff.
Johan contacted Lars, asking him about the municipal equestrian school and his thoughts about how he could help. Lars explained that unfortunately there was no easy answer, as every riding arena has its own unique conditions. He went on to describe how, during his 40 years working in the field, he had not come across a single material that provides a surface with even flexibility, joking that it would be ideal if someone could come up with a material that featured consistent cushioning across the entire surface – a kind of ‘rubber concrete’. With his entrepreneurial spirit, Johan resolved to turn Lars’ jokey aside into a serious reality.
The very next day, Johan called a friend who managed a concrete factory and asked to use the factory’s laboratory. Here, he began mixing and combining different quantities of rubber and concrete. After three days with little success, the mixture began to resemble rubber concrete. Johan called Lars and announced that he now had the requested material, which he could come and collect from Gothenburg. Filled with enthusiasm and surprise, and not yet entirely convinced that the results could be all he had hoped for, Lars travelled to the lab the same day. A couple of days later, it was Lars who contacted Johan to confirm that the mixture was indeed excellent.
Rubber Concrete becomes a fact
Without any clearly formulated idea about where their meeting would lead, this moment – albeit as yet unknown to Johan and Lars – was to become the beginning of something that Johan himself describes as “wonderful”: Rubber Concrete, the company that they now run together.
Two thousand attempts
Since the creation of those first mixtures in the laboratory, they have experimented with, mixed and tested many different variations. And the process has not always been easy. Out of around two thousand tests, about nineteen hundred have not worked out as intended. According to Johan, this is because you have a hard material meeting a soft one – something that shouldn’t actually work. However, with a combination of determination, curiosity and patience – as well as Johan’s ever-present motto “But what if it does?” – it did work in the end.
Recycled tyres
Rubber Concrete has entered into partnership with the Swedish Tyre Recycling Association (SDAB), a non-profit company which organises the collection and recycling of used tyres in Sweden based on the statutory producer responsibility for tyres. SDAB supplies worn-out tyres to Rubber Concrete, which then uses them as a raw material to be mixed with concrete. The resulting product is rubber concrete. Tyres usually have a lifespan of around four years, but when mixed into concrete this can be extended by at least 25 years.
“It’s fantastic that we can use a product which was originally intended for one use, and then recycle it and use it for a completely different purpose,” enthuses Johan.
Two materials for equestrian use
Rubber Concrete now manufactures products with two different types of rubber concrete. One is used to make walls for stables, while the other is laid under the sand in riding arenas. Today, Rubber Concrete produces stable walls for the Swedish company Ydre Grinden, which has manufactured products for Swedish agriculture – primarily for stables and other livestock buildings – since the 1940s. Other projects undertaken by Rubber Concrete include creating a 600 m² rubber concrete floor for a veterinary clinic in Kungsbacka near Gothenburg.
A wealth of advantages
The company soon came to understand that its rubber concrete product offers a wealth of advantages, both in general terms but also specifically for horses and equestrianism. As Johan explains, concrete itself does not have any insulation value, but rubber does. It is also light and springy, almost slightly elastic, as well as having sound-damping properties and absorbing vibrations. This means that when stable walls are made with rubber concrete, it is less noisy when horses kick. When a horse jumps and lands, it exerts around two tonnes of pressure on one hoof. This energy needs to be absorbed somewhere, and rubber concrete can help.
A stable wall made from rubber concrete weighs around 50% less than regular concrete, making it considerably lighter. Johan describes how a 350 kg three-metre stable wall would have weighed considerably more had it been made from ordinary concrete. Another benefit of the company’s rubber material is its excellent drainage properties, bringing many advantages for stables.
Less risk of injury
When observing how a horse moves and deals with challenges, this is done on a hard surface – usually concrete or asphalt. If the horse doesn’t trust the surface, it will be quite tense. Johan says that the opposite has been seen when the surface is made from rubber concrete: the horse relaxes. Rubber concrete is also shock-absorbing, which reduces the risk of the horse being injured. Furthermore, the material can be used to avoid slippery stable walkways. If a horse slips, the risk of injury is extremely high. Rubber concrete, on the other hand, puts the horse on a much firmer footing.
Leaching tests
The structure of concrete can be compared to pasta dough, with the fine-grained sand being bound together with the cement and forming a glue. Rubber Concrete takes small particles – the dust created when shredding tyres – and uses them to make this ‘pasta dough’. The small particles are bound in with the larger particles, creating elasticity in the concrete. The company has conducted leaching tests, which show that rubber concrete does not leach any more than regular concrete. Working with SDAB and RISE Research Institutes of Sweden, Rubber Concrete has carried out ‘fire and ice’ tests, examining how the material behaves at temperatures of -20°C and 150°C.
A focus on rubber concrete buildings and horses
In summer 2021, Johan bought a farm with a stable and a manège which he fitted out with rubber concrete. The stable walls are made from rubber, cement and a small amount of admixture, but no ballast.
Rubber Concrete moved to new premises in Skepplanda on Sweden’s west coast in March 2022. Here, the company will produce rubber concrete on a larger scale, carrying out the entire process itself due to the product’s unique properties. Rubber Concrete is currently focusing on using the material in stables and riding arenas, but also intends to explore whether it can be used in housebuilding.
Johan believes that there are countless exciting applications for which investing in rubber concrete could – and should – be investigated, including its use in buildings. He explains that one challenge when building homes in cities relates to noise and vibrations, and so it is simply a matter of thinking about what the material could do – and this could lead to all sorts of possibilities. For the time being, however, the focus is firmly on horses and the equestrian industry – the field that Johan and Lars know best of all.