Much can be saved with in-situ reinforcement of the subsoil

But what is not in sight is perhaps just as special as the building itself: the Harderwijk-based RvB Group reinforced the subsoil in an extremely sustainable and innovative way, making foundation on piles unnecessary. 

"'Building on steel' is what we call it when we erect a building on solid ground," explains Roelof De Vries of the RvB Group. "That can offer advantages over building on piles. In many cases you can save on a thinner concrete floor or you need to use less reinforcing steel."

Incidentally, the Dutch subsurface is by no means always suitable for in-situ reinforcement, but RvB Group and business unit TerraStab are one of the few Dutch companies specialized in this method. De Vries: "We always look at it per site, but if we think the subsoil is suitable for improvement with the method we have developed, we advise the client and main structural engineer. For the construction of the warehouse in Haps, we did extensive research into the various soil layers, including probing and soil drilling. Because the load on the floors and subsoil will soon be enormous, partly because of the considerable height of the building and the products that will be stored there, you would need a large number of piles. But when you can reinforce the ground, that's not necessary."

Compacted

After soil testing and determining the weaker spots in the subsoil, the RvB Group's engineers and lab technicians investigate in their own laboratory whether that subsoil - with the addition of binders developed in-house - can be brought to the right strength. "In this case, that was quite possible," says De Vries. "Then our structural engineer consults our findings with the main structural engineer. In Haps, we ended up mixing the soil on site with our binder."

Besides saving on foundation piles and the thickness and reinforcement of the concrete floor, in-situ reinforcement has another advantage: the subsoil does not have to be moved. De Vries: "If, for example, there is PFAS in the soil that has to be removed, it can be quite expensive. With in-situ remediation you also limit the number of transport movements. So our method is quite sustainable and circular." 

RvB Group completely engineered and realized the civil part in a short time. "So in addition to taking care of the foundation, we also laid all cables, pipes, sewers and site paving, so that main contractor Martens could start work on a clean and ready site. All this in a tight schedule; Martens was very happy with it," De Vries concludes.