Talking Asphalt: Commercial pavement repair — April 2011

Talking Asphalt: Commercial pavement repair -- April 2011At the Asphalt Institute, we get many inquiries requesting assistance or advice on repairing parking lots, access roads and other commercial (and residential) pavements. The typical inquiry goes something like, “I have this parking lot (or I represent a property owners’ association), and our pavement needs some work. I need some help.”

In fact, the first email I received in response to this column started off just that way. At AI, we are not staffed to respond to these requests, so I thought I would try to provide some guidance in this month’s column.

It is a fact of ownership that pavements eventually will need some remedial work. And there is a process for getting the work done. I’ll try to go through a summary of the process here. It is not a particularly difficult deal; it just involves a series of steps which must be followed.

Step 1. Get professional help. You likely have a considerable investment in your pavement. You need to hire a competent, local expert. Competent—because there is knowledge and experience involved. And local, because knowledge of the locally available materials and services is important. A pavement professional should not try to sell you something; he should assess the problem and make recommendations for repairs.

For homeowners, with small driveway repairs, hiring a pavement consultant is probably not practical. In this case, it becomes more important to find the right contractor. More on that below.

Step 2. Determine the cause of the pavement distress. There is no way to make an effective repair without identifying and addressing the cause of the problem. This is where the pavement professional comes in.

In determining the cause of the existing problems, there are several things to look for. Drainage and too little pavement structure (either support or thickness) are common causes of pavement failure. Other causes include poor materials and/or construction of the existing pavement and simple wear-and-tear.

So, is the distress related to a drainage problem? Is the foundation solid? Is there sufficient pavement structure/thickness to carry the loads? Delivery trucks in commercial developments need more pavement thickness than cars. Similarly, garbage trucks can be heavy and need additional support.

Is the problem due to poor construction of the original pavement? Examples of poor construction are joint failures and segregated (open) areas (which eventually become potholes).

Maybe the problem is that the pavement is just getting old. Pavement surfaces are like shingle roofs on houses. After enough time, they become brittle and dry and need to be replaced.

Step 3. Have a written plan for the repair work. This needs to provide detailed, written instructions, including the scope of work, prep work details, mix type, compacted thicknesses of layers, and placement and compaction requirements. Also include any warranty information, time frame and scheduling limits, and clean-up details.

I stress “compacted” thickness because quoting estimates based on loose layer thicknesses is misleading. This may result in a lower price but a poorer pavement. All pavement designs are based on compacted layer thicknesses. The strength and quality of a pavement is largely controlled by the compaction, and there must be enough thickness placed to allow for the asphalt-coated stone particles to re-orient under the rollerin addition to having enough structure to support the loads. More on construction later.

Your pavement consultant can help develop the job documents.

Step 4. Selecting a contractor. This is probably the most critical part. The lowest price is not necessarily the best price. Ask around, if you see a job that looks good, ask who did it. Once you think you know who you want to do the work, ask to see examples of their work and check their references. Check with the Better Business Bureau. Do your homework now; it may take a little time and effort to find a good contractor, but it is worth the trouble.

Step 5. Construction details. Choosing the right materials for the repairs is important. For the base layer(s), a stable mix is needed. For the surface, a workable, smooth-textured mix is generally preferred. The old pavement should be prepped before the new paving begins. Any drainage problems have to be corrected. All failed material has to be removed. A bond or tack coat should be applied to the old pavement before placing the new mix.

Workmanship is critical. Segregation of the asphalt mixture must be minimized at the plant and at the paving site. This includes not doing excess hand-working of the mix. You can mess up a good mat by over-raking and by throwing back the collected loose coarse particles.

Compaction is absolutely critical. Maintain the temperature of the mix; roll the mix while it is still compactable. Work quickly and with sufficient size and numbers of equipment. Apply proper joint construction techniques.

Last Step. Maintenance. After you have a good repair job in place, timely maintenance and preservation are the keys to achieving long pavement life and avoiding costly, premature failures. But that?s the subject of another column.

Helpful publications. I can’t cover every detail of repair work here, and I have tried to hit the high points. But if you follow the process/path outlined here, you have made a good start.

The Asphalt Institute has several very good publications which can help you with this type of effort. One I highly recommend is “MS-4, The Asphalt Handbook.” I call this one the “encyclopedia of asphalt.” It covers most everything you need to work with asphalt. And if you want more details, AI has additional manuals on pavement design, construction, and maintenance.