How do you actually know when a concrete casting has fully hardened?
The temperature tells about the hardening
The answer is that you can measure it by the temperature inside the concrete. That is, if you have a temperature sensor in there – and a device that can read the sensor. The combination of sensors, devices for reading and advanced software for that exercise is the Danish tech company Maturix’s speciality. Maturix has just won the contract to supply that solution for the Fehmarn project.
801 segments and a portal
89 tunnel elements are to be used for the Fehmarn Tunnel. Each element consists of nine segments, which are cast at the element factory in Rødbyhavn. That leaves 801 tunnel segments to keep an eye on. To this must be added the large tunnel portal, which is also an enormous concrete construction. And many places must be measured at the same time in each casting, so just like everything else about the Fehmarn project, the measurements are also an undertaking of an out-of-the-ordinary scope:
Right in the backyard
– It is not our biggest project, but it is one of the big ones, says Tobias Ejersbo, who is CEO of Odense-based Maturix.
– And it’s funny that it’s a project right here in our backyard – and not in the Ivory Coast or somewhere else abroad, says Tobias Ejersbo.
Sensor is moulded in
Maturix’s system can measure how concrete hardens. The system works by moulding a small temperature sensor in the form of a thin metal wire into the construction. Then you can continuously monitor the temperature inside the concrete on a wireless terminal. That temperature can be used as an indication of how far along the casting is in the curing process. And when you then combine that data with the temperature around the casting, you can also come up with a precise forecast of when the concrete has fully hardened.
Patents on the technology
Danish Maturix is one of less than a handful of companies in the world that can supply equipment that is precise enough for use in, for example, tunnel projects. Maturix also has a few patents on the technology. But it is also practical for much smaller projects, emphasizes the director:
– It can also be a drain for a campus building or a silo, says Tobias Ejersbo.
Even though the Fehmarn contract is one of the more fun ones, the company does not expect that they will beat the drum much on that particular project:
Can’t show off much
– It’s not a project we can brag about, because we are tied hand and foot when it comes to talking about the concrete content of the contract, says Tobias Ejersbo, referring to the NDAs (Non-Disclosure Agreement) that typically comes with a supplier contract with FLC or FBC. And Maturix must deliver to both consortia, as FBC is responsible for part of the tunnel portal, while FLC is responsible for the actual tunnel construction and the element factory.
Feelers out for years
– We got the contract after a tender that we bid for. But prior to that, we have had the feelers out since 2017-2018, when there were conferences and the like about the Fehmarn project, says Tobias Ejersbo. That advice has been passed on.
