Photo: Mikal Schlosser

New sensors function as eyes in concrete

Tuesday 26 Jul 16
by Marianne Vang Ryde

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A new spin-out from DTU has recently marketed a sensor system allowing you to monitor activity inside concrete structures from your desk.

For some time, DTU Fotonik has been developing optical fibres made of Plexiglas for different purposes. And recently the researchers have discovered that optical fibres can be equipped with sensors for measuring moisture, temperature, and load. When embedding the flexible and durable plastic sensors into the concrete, they can simply function as eyes in the concrete. The idea has resulted in the spin-out Shute.

One of the founders of the company is Kristian Nielsen, Development Engineer, and he says:

“Embedding sensors into concrete isn’t something new, but you would normally use electrical temperature sensors which are only capable of measuring one point and require two cables per measuring point. Experiments have been conducted using glass fibres, but glass is more rigid than plastic and breaks easily. Concrete is cast using cement and aggregate, and during the drying process, the aggregate risks moving and breaking the glass. Our sensor, however, can be stretched and bent without being damaged.”

The new sensor is connected to a light source and a light analyser. When transmitting laser light into the fibre, the light penetrates the fibre and is reflected by the measuring point, after which the analyser detects what has happened at the measuring point. The analysis continues on a computer, and the client is then able to monitor the process at home. 

The company is quite new and therefore still in the process of documenting the durability of the product. But the first results are rolling in, for instance in connection with NCC Building, one of the leading construction and property development companies in Northern Europe, which has cast the plastic fibre sensor into one of their floors.

“During the construction phase, it’s very important to keep focus on the moisture level of the concrete, especially if installing wooden floors over the concrete. To ensure that the concrete has the right moisture level, we normally take samples, but the Shut sensor system allows us to monitor the drying process and continue the work as soon as the moisture level is satisfactory. If it works as intended, we will be able to save time and possibly money, and we avoid having to take regular samples from the concrete. Another advantage is that we obtain data on the drying which we can use throughout the entire construction process,” says Timmi Sargentoni, Contract Manager at NCC.

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