- Patching and Edge Repair
Patching is one of the most expensive maintenance procedures for hot-mix asphalt (HMA) pavements, (per unit of measure such as cost/ton, cost/in2, or cost/yd2). It is routinely done prior to other forms of corrective maintenance, pavement preservation, or pre-treatment prior to an overlay. If done correctly, patching restores the pavement surface to a state in which subsequent preservation treatments will have a much better chance of success.
The primary methods of patching include the replacement of materials that have been lost due to localized pavement distress or disintegration, the complete removal (dig out) and replacement of continuous segments of failed pavement, or the application of a thin layer of HMA material over segments of pavement that exhibit more surface-related distress/distortion. Once patched, the distressed area is repaired or strengthened so that it can carry a significant traffic level with improved performance and slower rates of deterioration.
Patching may be temporary, semi-permanent, or permanent. The appropriate method depends on the traffic level, the time of the year during which the repair is made, the time until scheduled rehabilitation, and the availability of equipment and personnel.
Patching is best carried out during clear moderate weather. However, emergency repairs made in less than ideal weather conditions may adversely affect the patch durability such that the patch should be considered “temporary.” In this case, one should plan for a more semi-permanent when moderate weather conditions allow.
Before discussing the procedures and materials used for the various treatments let’s consider the terminology.
Patching is a process in which the material in a highly distressed area is either removed/replaced or additional material is added to cover up the distressed area. Merely filling a hole will not prevent the development of distress adjacent to or within the patch in many instances. Maximum performance is achieved when the boundaries of the distressed area are appropriately marked and cut, the failed material is removed, the remaining (underlying) material is re-compacted, the hole is properly prepared, and new material is added and compacted to a level similar to that for a new pavement.
The primary methods for pothole patching include temporary, semi-permanent and injection. The primary materials used include the following:
• hot-mix asphalt (preferred);
• cold-mix asphalt (temporary fix only);
• aggregate/asphalt emulsion combinations (ie, injection patching); and
• special patching mixes.
Dig outs are used when the pavement has failed in localized areas. The failure may be the result of one or more factors ? underlying support materials have disintegrated, become infiltrated with fine-grained materials and/or lost their load-carrying capacity. Unlike typical patching, dig outs require the removal and replacement of most, if not all, of the underlying base/sub base materials. The preferred material for dig outs is HMA, whereas cold mix is recommended for an emergency or temporary fix.
Edge repairs are required when the pavement has failed along the edges due to the action of traffic and the loss of edge support that occurs due to the presence of water, aggressive-vegetation growth, and material erosion due to wind or traffic. As the name implies, edge failures are not in the primary wheel path, but their presence can accelerate the normal deterioration of the pavement. The materials used for edge repairs are the same as those associated with patching and dig outs.
The main method used for surface reinstatement is skin patching. Typically, a thin layer of HMA or a cold mix blanket is applied to the existing surface or an emulsion is applied and covered with a layer of aggregate. The aggregate is either a washed sand or fine aggregate.
Next week, more on pothole patching and dig outs.
1) Caltrans, Maintenance Technical Advisory Guide, Volume I, Flexible Pavement Preservation, Second Edition, 2008.
2) T Wilson and A Romine, Materials and Procedures for Repair of Potholes in Asphalt- Surface Pavements, FHWA-RD-99-168, Washington, DC, 1999.
- About Century Paving
Century Paving is a general engineering contractor specializing in asphalt and concrete maintenance and repair. We offer a complete line of services to support your maintenance needs. Century Paving is based in Southern California and has a sister office in Northern California. Century Paving was established in 1974 and has successfully completed over 10,000 projects both large and small. Our staff and crews focus on quality work at a reasonable price.
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