More weight, less volume seems the most obvious reason to use MagnaDense concrete for a counterweight in a bridge because dimensions are often limited.
However, there are additional reasons to opt for high density concrete with our heavy magnetite aggregate.
New Kogerpolderbridge needs counterweight
The Kogerpolderbridge in the North-Holland province in The Netherlands needed replacement because it was at the end of its lifetime.
It was not a case of simple exchange; the authorities took the opportunity to make the bridge wider and create a different lane strategy on the bridge itself. Like many other Dutch bridges, this one now also has a separate lane for bicycles.
Because the authorities wanted to redesign the bridge completely, it was the perfect opportunity for the engineering and constructing company to include a MagnaDense concrete-based counterweight.
Alternative counterweight solutions vs high density concrete
“We’ve used a traditional concrete mix design for this project as this can achieve an even higher density than self-compacting concrete. This mix design was also better to guarantee a homogeneous mix and density at any point in the counterweight, which is crucial for this bascule bridge.” Daan Claessens, Project Coordinator for the engineering and constructing company SPIE, tells us.
Finally, the engineering company concluded that the most economical and design-fitting solution would be to use a magnetite aggregate to mix into the concrete.
Benefits of using heavyweight concrete
“Another benefit we got from using dense aggregate is the ease of use,” says Claessens. He continues, “In the alternative situation, after filling the counterweight with steel elements, you still had to pour everything in concrete, and weld large steel plates on it. Using high density concrete allows the contractor to pour the counterweight through holes. Finally, on these holes, they only have to bolt some smaller plates.”
“The third benefit we noticed from using MagnaDense concrete is time savings. We usually apply the counterweight of such a bridge during a blockage period where we need to do everything quickly. Therefore, saving time by not having to hoist crates with steel is very desirable. After applying the counterweight, there was no longer a need to weld plates, which no longer blocks the location for other work in the bridge cellar,” Daan Claessens concludes.
Custom-made MagnaDense solution
A crucial detail for this bascule bridge construction is that the high density concrete will be poured into place to create the counterweight with the bridge closed. As you might imagine, this being an existing water route, the contractor does not wish to maintain this bridge closed for any longer than necessary.
To make sure the concrete mixing company can create the perfect homogenous product, we supply a pre-blend of our MagnaDense 2 and MagnaDense 20S grades. The final density of the heavy concrete counterweight for this project is 3850 kg/m3.
Casting a bridge counterweight on-site
Fortunately, the casting of the counterweight could take place at the scheduled date. “During the concrete pouring we weighted the final counterweight, and this went according to expectations”, Daan lets us know.
The ballast crate has five chambers that are now filled with MagnaDense concrete. The construction company cast around 51 cubic metres heavyweight concrete in this project.
International references for bridge projects
Construction companies build a variety of well-known bridges which include the LKAB Minerals natural mineral magnetite. Examples of international bridges using our natural MagnaDense are:
- Samuel Beckett bridge – Ireland
- Kallo Sluice bridge – Belgium
- Öresunds bridge – Sweden/Denmark
- Great Belt bridge – Denmark
For some of these projects, we have a FREE detailed Case Study available upon request. Check for more information with your local sales manager.
Redesign and replacement of the existing Kogerpolderbrug bascule bridge and placement of a counterweight filled with high density concrete.