Expansion joints in overpasses and bridges are often the Achilles’ heel of the road network. Due to the combination of movements that occur, they can be difficult and time-consuming to construct. These types of joints can require a great deal of maintenance. Their repair or replacement takes up a lot of time and requires lengthy road closures. In addition, the costs associated with damaged expansion joints are substantial for both the road owner and road user.

The most durable expansion joints have hard edges with a rubber profile between them. These often produce a considerable rumbling, pulsing sound when being driven across, which is often intensified by the “sound box” under the overpass. The pulsing sound when driving over the joints becomes an unacceptable nuisance and hinders the quality of life in busy urban areas.

The market has been demanding low-maintenance and silent expansion joints for some time. Bituminous (seamless) joints are often used, which generate little to no pulsing sound. However the lifespan of this type of expansion joint is substantially shorter than the surface layer, thus often requiring maintenance cycles.

The solution? Brainjoint

The market has a need for silent expansion joints with a lifespan that corresponds to the surface layer. Heijmans has responded to this market demand with the Brainjoint, an extremely quiet expansion joint that absorbs and distributes the movements of the bridge or overpass . This allows for the asphalt layer to be applied seamlessly over the joint. Brainjoint stands for “Buried Reinforced Asphalt Interlayer Noiseless Joint”. In other words, it is a concealed, invisible and silent joint based on special interlayers in the asphalt construction. The advantages of the Brainjoint are threefold: noiseless, easy to install and lower in maintenance.

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Brainjoint construction: The bridge deck (1) is constructed on the abutment surface of the bridge or overpass. A layer of thick asphalt concrete (2) is then applied to the bridge deck. A force-distributing insert (4) is added to the joint between this layer and Brugflex asphalt (3).

Construction

The most important feature of the Brainjoint is that it consists of several layers of asphalt. These layers can also be applied to the overpass directly. With this approach, there is no disruption of the surface layer of the asphalt construction before and after the joint. Moreover, during construction, application of the joint can be done by regular asphalt crews. There will be no hard edges in the driving lane that may cause pulsing noises. This way, there is no actual joint. Construction time is also considerably shorter compared to other types of expansion joints so the number and frequency of maintenance cycles can be significantly reduced. Another advantage of the Brainjoint is that it can be installed both as an individual joint construction and as an integral part of a completely new asphalt package on and around an overpass. It can be used in both existing and new overpasses, integral and traditional structures with span lengths of around 50 meters and transitional structures at the end of baffle plates in integral structures.

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Left: Installing the Brainjoint. Right: Invisible Brainjoint after adding asphalt layer.

Applications

The main road network in the Netherlands has many bridges and overpasses. The provincial road network also includes large numbers of structures, many of which are suitable for using the Brainjoint. In short, there are tens of thousands of potential meters of road that can be fitted with the Brainjoint. The Brainjoint was used on a major scale for the first time in September 2014, when placing of a new layer of asphalt on the A27 motorway in the Netherlands as part of maintenance work. The bituminous joints in 56 expansion joints with a total length of 695 meters (7000 feet) were replaced by the Brainjoint. This road has become quieter and more comfortable to drive on and, thanks to the use of the Brainjoint, there will be little to no need for more maintenance work on the joints over the next few years.

Since the first Brainjoint was applied, many more projects have followed, to the extent that other contractors have used the system to build and/or replace joints.

The Brainjoint was used for the very first time back in 2009 as part of the competition for "silent expansion joints" launched by the Dutch Ministry of Waterways and Public Works (Rijkswaterstaat). The A50 motorway in the Netherlands has a test lane with silent joints from four different market players. An inspection in 2014 showed that the Brainjoint is still intact on this section of road.