An edge break is damage caused to the edge of the road surface due to the lack of lateral support afforded to the base and surfacing by the gravel shoulder. This lack of support may arise from a number of factors, such as tyre action on the gravel adjacent to the surfaced edge, water scouring and wind eddies from passing vehicles removing fines from the gravel shoulder. Edge breaks have the effect of reducing the road width and forming deep furrows at the edge, both a hazard to traffic.
Paveking repairs edge breaks using a range of materials. The method described will deal only with the repair of deep edge breaks with bitumen stabilized material and asphalt surfacing.
Bitumen stabilized material: The bitumen stabilized material consisting of a combination of aggregates is used to meet the recommended grading.
Wearing course asphalt: Either hot mix, or (bagged) cold mix asphalt can be used depending on the location, traffic and availability of materials.
Bitumen emulsion: Anionic stable mix grade bitumen 60% emulsion, diluted in equal parts with water is recommended as a tack for the edge break operation as is breaks more rapidly and allows the work to be completed sooner.
Solvent/water: Used to clean the equipment after use if an emulsion is used.
Sealant: A bitumen emulsion to seal over the edge break edges once repaired to prevent moisture ingress and seal off the top surface of the repaired pothole.
Shoulder gravel: Used to ensure a smooth transition from wearing course to the shoulder as well as to provide support to the area that has been repaired.
Some important aspects that Paveking pays attention to:
Compaction in the repair area should be applied in such a manner so as not to damage the existing surrounding pavement layers;
Bitumen stabilized material requires some time to set and harden. The wearing course should only be applied once the bitumen stabilized material layer has set sufficiently;
Regarding the selection of wearing course asphalt for a particular maintenance operation, the following factors need to be considered:
o Hot mix asphalt allows the road to be opened to traffic once it has cooled which is soon after the repair is complete, resulting in less traffic disruptions and earlier removal. As it is important to ensure that the HMA remains hot enough to be compacted, there is a risk of wastage.
o Cold mix asphalt wearing course can only be opened to traffic once the volatiles in the mixture have evaporated to prevent the layer yielding under traffic. Consequently, the repair area may cause an obstruction with signage having to be in place, typically overnight.
As with all repairs to roads under traffic, it is vitally important that road users are aware of the roadworks through proper signage and traffic accommodation