Anchoring any device to an asphalt roadway is quite different from anchoring to concrete surfaces. Asphalt in made of small aggregate stones, held together by the bitumen blacktop. Over time, or under continuous pressure, the bitumen flows like a liquid, and the surfcae yields.
There are 4 ways to permanently attach devices to asphalt:
Adhesive: This is the simplest way, but it may not work reliably on older surfaces and it will offer a limited force resistance. The failure mode of gluing metal plates to asphalt is that the asphalt layer close to the surface peels off and the plate comes away with about 5mm (1/4") of asphalt. This does not happen overnight, and clearly depends on the quality of the surface as well as on the forces involved. We do not recommend using adhesive alone for the installation of our MySpot 200 barriers, but it is likely to produce good results for the MySpot 120.
Anchors: MySpot barriers are provided with CA6 concrete anchors (DPC part number 01-6305). These work superbly on masonry surfaces, but are not suitable for attaching barriers to asphalt. Optional asphalt anchors are available (SP14 family). Full information on these is available on this web site.
There are a few 3rd party asphalt anchors on the market. They use an adhesive to fill in the drilled hole in the asphalt, and the anchor is then pushed in or threaded in. One source is Hilti which offer short anchors offering a low pull resistance. Another source is Designated Parking (that is us); we make a specially long asphalt anchor (SP14)
that has been proven to work well with the MySpot 200 and other structures (signs, bike racks and more).
Anchors Plus Adhesive: This provides a reliable method for mounting our barriers to asphalt. Adding adhesive to attach the mounting plates to the ground reduces the sideways sliding forces on the anchors, which would over time loosen the asphalt and allow the anchors to lift.
Concrete Patches: This is the most reliable method, but likely to be the more expensive solution. The surface where the mounting bolts need to attach to the ground is drilled out to a radius of at least 3" (150mm diameter) to a depth of at least 7" (180 mm). The asphalt is removed and concrete is pured in instead. Once the concrete hardened, concrete anchors are installed as usual.
An application note covering this topic can be found and downloaded here.
