Talking Asphalt: Paving Parking Lots - February 2013
If you have been following my blog, you know that I focus a lot on commercial paving, driveways, parking lots and related pavements. I do this because I believe there is a need to improve this segment of the asphalt industry. Many commercial paving firms do very good work, but unfortunately, I’ve seen many poor commercial jobs.
In many cases, the pavement owner shares the responsibility for their poor performing pavements. There are poor, or no, specifications, and adequate inspection is not performed. The paving contractor needs a clear and detailed description of the owner’s expectations, and the owner needs to monitor the work as it progresses to make sure it is satisfactory. It is too late to identify shortcomings after the work is done.
Start the process of building a top performing parking lot (or other commercial paving) by choosing a competent contractor. Choose one who has experience and skilled personnel, adequate equipment and good references. Remember the lowest price may not be the best deal. Make sure both parties know the scope of work to be delivered.
A good pavement starts with a good foundation. If it is a new pavement, know the quality and strength of the subgrade soil. Make sure the subgrade is well compacted (proof roll it, etc.) Use a pavement thickness appropriate for the traffic the pavement will carry. Passenger vehicles (cars and SUVs, not buses) require only a minimal thickness, but commercial trucks absolutely require additional pavement structure (thickness.) Heads up! Garbage trucks can destroy a thin pavement. It’s good practice to build a thicker pavement at dumpster sites, loading docks and similar locations.
If you are doing a resurfacing job, take the time and effort to repair any failed areas. Soft spots need to be cut out and rebuilt. Potholes have to be addressed. Seal the cracks; apply reinforcing fabric, as needed. Clean the surface and apply a good tack coat. Minimize the handwork; let the paver place the mix.
Don’t forget about drainage. Water can undermine a pavement and cause early failures. You have to plan for both surface and sub-surface water. Provide adequate slope so the water drains. Also, you need to select a mix that will provide a tight surface texture to lessen moisture intrusion. Generally, fine graded mixes with relatively high asphalt contents are suited for parking lots. High traffic areas or locations subject to heavy loads may need more specialized mixes.
Proper compaction is critical for all pavements. Commercial jobs are no exception. Dense graded mixes should be compacted to an in-place air voids content of 8 percent or less. Higher voids contents allow water and air to enter the pavement and cause damage. Poorly compacted mixes are subject to durability problems such as potholes and raveling.
No new information here; just a reminder of some of the keys to good performance of commercial paving. Let’s build better pavements.
Email Dwight at firstname.lastname@example.org