Asphalt Overlay

St. Mary's County's overlay program is used to restore paved road surfaces to add structural capacity, riding comfort and skid resistance which add to the road's safety. While newly overlaid roads are aesthetically pleasing, roads are not overlaid to improve appearance. Pavement deterioration is cumulative. Factors including weather, traffic impacts, frequency of maintenance etc. all contribute to a roads longevity. The average life of a paved road in St. Mary's County is between 15 and 20 years (that is from the time the road is newly paved to a point where reconstruction becomes necessary). When a paved road reaches about 75% of its service life deterioration accelerates. If routine maintenance is not performed restoration costs are four to five times higher. Please refer to our Asphalt Overlay Program Listing for additional information.

Pavement Preparation

It is the contractor's responsibility to sweep and remove any soil, sod or debris from the area of the roadway surface and to otherwise prepare the existing pavement for resurfacing. Any roadway in St. Mary's County in need of maintenance patching / base repair may be identified by the Inspector and performed under this contract. Areas that are to be patched are marked by the Inspector and include broken pavements and pipe crossings. For County construction projects, please view our Overlay Preparation page.

Application

The asphalt overlay program widens, improves drainage, and extends the service life of a road up to fifteen (15) years. Approximately $3,000,000 per year is now dedicated to this program, which results in the improvement of between 10-15 miles of County-maintained roadways. Overlay thicknesses vary from 2" to 4" and work is usually performed between April 15th and November 15th. All pavements that are striped and/or otherwise marked with paint are swept to remove loose stones and debris to assure maximum adhesion. Shoulder adjustments must also be made to provide the needed lateral structural support for the new surface and to raise the shoulder to the proper elevation and cross-slope. Any full depth patching, paving fabric or culvert repairs are also performed in preparation for an asphalt overlay. The greatest advantage of this application is that the roadway surface may be immediately opened to traffic.

Cape Seal

It is often that a surface treatment is subsequently slurried (cape sealed) or overlaid with asphalt the following year(s). Cape Seals are used where a chip seal is too rough and requires a smooth finish, for example in residential streets. In instances where cracking is a problem a chip seal can alleviate cracking and the slurry can provide the smooth and hard wearing surface. The addition of a slurry capping not only makes the surface smooth but locks the aggregate of the chip seal in place eliminating stone loss. A cape seal can last longer, can treat cracks, is smoother than a chip seal, more durable than a slurry and could last as long as ten (10) years depending on traffic volumes.

Alternatives

As landfill costs for construction and demolition debris continue to rise it makes sense to seek alternative means of disposal of asphalt that is removed during construction of roadways. The Department is considering the use of recycled asphalt, "RAP" ,as an economical alternative to new asphalt. RAP is already being used and approved on many new subdivision streets. The level of recycled asphalt that can be used on a project varies, typically 10-20% recycled material is incorporated into mixes. In many cases this application can significantly reduce costs, but from a performance standpoint has a higher occurrence of pot-holing. Hot In-Place Recycling, "HIPR", is a process of correcting asphalt pavement surface distress by softening the existing surface with heat; mechanically removing the pavement surface; mixing with a recycling agent; possibly adding virgin asphalt and/or aggregate; and placing it on the pavement without removing the recycled material from the original site. The existing pavement must be structurally sound because this process is limited to surface rehabilitation. This alternative is viable for asphalt pavements with a thickness of at least 3 inches. The process can be performed in a single pass which recombines the restored pavement with virgin material which also minimizes traffic disruptions; or a two-pass procedure in which the restored material is re-compacted and a separate new wearing surface is later applied. For larger scaled projects, when all factors are considered, a savings of between 10-50% may be achieved when a 1 inch HIPR layer is applied in lieu of a new 1 inch overlay.

Parking

During an overlay project, residents must remove all vehicles from the street. If curb and gutter is present the old pavement will be milled along each edge so that when the overlay is applied the surface of the new pavement is level with the gutter. The street is then sprayed with a thin layer of asphalt called a tack coat to ensure the new pavement will adhere to the old pavement. Once the overlay is applied, it would be ideal for traffic to be kept off the new pavement for at least four (4) hours. Traffic may travel on a newly paved roadway after it has been rolled once. It is preferred, however, to have the second rolling completed prior to opening up the road to traffic. Sharp turning movements on the new surface must be avoided until the pavement has had a chance to cure. Operations are performed to ensure at least one lane of traffic remains open at all times.