Dina Kuttah's idea could change road technology

It began with an idea, but eight years work and fifteen academic papers later the result is a machine that might well prove to be a game-changer in road technology, not only in Sweden, but worldwide. The inventor is also hopeful that it will eventually be a commercial success.

– “Yes, that’s one objective. But not yet. First we need to make the machine more sustainable and conduct further trials. It also needs a shell, or bodywork,” says VTI senior researcher and innovator Dina Kuttah.

Let us start from the beginning. Measuring permanent deformations from dynamic loads in road layers, from the pavement to the subgrade, has long been a challenge for researchers and engineers. The two most common methods are to use very heavy machinery such as VTI’s Heavy Vehicle Simulator (HVS) – which is precise but very expensive – or to test the material in a laboratory, which has the disadvantage of no longer reflecting the state of the material in field conditions.

Falling weight deflectometer measurement (FWD), the method previously used, is unable to differentiate between permanent and temporary deformation in road layers. The test method is also limited to six repeated drops, which is insufficient to obtain the parameters needed for road design.

“This was what got me thinking: How could we measure cheaply and precisely in the field? When I couldn’t find anything on line, I decided to develop something myself,” explains Kuttah.

The machine standing in VTI’s garage eight years later was built by KUAB based on the VTI researcher’s concept. It is a development of an earlier project called the Repeated Lightweight Deflectometer (RLWD), two manual versions of which were built. This third version is automated. What appears to the layman to be a fairly complex metal construction of beams, chains, sensors, plates and springs comprises the Automized Lightweight Deflectometer (ALWD).

The machine works by repeatedly raising a baseplate and dropping it onto a surface of packed material and measuring the deformation. By varying the diameter of the plate and the drop height, the pressure can be adjusted from 20 to 200 kilopascals. The number of drops is programmed by the operator, after which the process is fully automated; thus far, a cycle of 10,000 drops has been achieved.

Compared to existing field equipment, the main advantages of the ALWD are that it is automated, that it can perform a large number of pressure tests, and that it can distinguish between temporary and permanent deformations. The last of these is accomplished using a small beam at the side of the baseplate.

“This makes it both cheaper and easier to collect data on different road materials, data that is vital to designing roads optimally in future,” says Kuttah.

The VTI researcher is a member of the Swedish Inventors Association (SUF) and has registered her idea for a modified deflectometer through the association.

Translation: CBG