Condominiums and HOA communities often discover their asphalt roads, parking lots, and driveways are their most valuable assets. Not just in terms of capital costs, but also safety and curb appeal. These highly visible components periodically become major points of discussion at board or committee meetings. If one of those types of meetings is in your future, this article may serve as a primer for paving facts. There is no better way to have a meeting’s agenda go astray when no one knows the difference or benefits of sealcoating vs. an asphalt overlay.
So let us start with the basics. Asphalt pavement is bituminous concrete and called ‘concrete’ because like cement-based concrete, bituminous concrete has a mineral aggregate of stone and sand. This aggregate is held together with a binder of petroleum derivative asphalt. Its advantage over concrete is that it is more flexible and less expensive than concrete pavement. It also manages de-icing salt and sub-surface movement better than concrete.
Beneath typical roadways there is a sub-base of 4 to 8 inches of a well drained, compacted soil and gravel mix. The first layer of paving called the binder course is 1 ½ to 2 inches thick and covered by a topping coat of 1 ½ inches. If it were not for the sun and water, asphalt paving would last a long time, but paving begins to deteriorate as soon as water begins to penetrate the binder course and the UV rays remove asphalt from the topping coat. This can happen in less than five years. This is why adding a sealing coat in the first 2 to 5 years is recommended.
Sealing coat materials do not add back the asphalt lost due to UV deterioration. It only protects the pavement for a brief time from further deterioration such as shrinkage cracks and raveling (loss of surface aggregate). It does not bridge large cracks or fill roadway depressions. Therefore, if the pavement is over five years old and has never been seal coated, it has lost its chance for physical benefit to the life of the pavement. At that point it is only a cosmetic remedy.
When water begins to infiltrate the pavement, the freeze/thaw cycle takes its toll. The small cracks become larger in the binder course and eventually the sub-base begins to fail. At this point surface cracks, settlement, alligatoring, and other surface visible signs including potholes make an appearance. Your Preventive Maintenance Plan should include the filling of these cracks with standard joint filler to within 1/8 to ¼ inch of the top of the crack. Potholes and other localized damage can be cut out and filled with patching material as needed.
Similarly, surface depressions and sink areas should be annually addressed as well. These problems are typically due to poor sub-surface soil conditions causing continued settlement. It is important to not allow ponding of water in the roadway or parking lot to minimize water infiltration, hydroplaning, and eliminate slipping hazards.
The deteriorated paving conditions sometimes allow the postponement of a major project with all its attending traffic and extended project schedules with the use of an Overlay repair. This method uses an overlayment of asphalt material on top of the existing surface extending the life of the pavement and postponing complete reconstruction. An overlay is applied with or without a geotextile fabric layer. If an overlay solution is not suitable then a pavement reconstruction repair method is needed such as Milling and Asphalt Replacement (MAR) or Full-Depth Repair (FDR).
Milling and Asphalt Replacement projects use a milling machine on the top surface to a depth of 1 to 2 inches. The removed material is hauled to a recycling facility and is replaced with a new asphalt mix often containing recycled asphalt pavement (RAP). This method can add 10 to 15 years of life to the current roadway.
If the sub-base has failed, a Full-Depth Repair may be the only option. This may require removal of large areas of deterioration and repairing the sub-base followed by a 1 ½ inch binder with a 1 ½ inch top layer. If the roadway or parking area deterioration is widespread, the options include a reclamation project where the top 6 to 12 inches of pavement and sub-base is ground into a recycled material used for a compacted and graded foundation for a new paving surface with a life expectancy of 20 to 25 years.
Finally, paving projects are not just about bituminous concrete but also pavement markings. ADA and other safety codes have changed since the last pavement marking project. The parking lots and other areas need careful consideration of the new pavement markings impact on safety, parking efficiency, and local compliance as well as choosing the type of paint to use. This would also be a suitable time to consider the painting or improvement of bollards, car stops, and light pole bases. As with any endeavor, preparation and forethought are key to a successful project. Plan to succeed.
Written by Jack Carr, P.E., R.S., LEED-AP, Senior Consultant Criterium Engineers
Published in Condo Media