Statewide Asphalt

Asphalt Paving

Two Types of Asphalt Paving

There are actually two general types of asphalt paving: one which is done as part of a new or re-construction project, and one which is an overlay.

The first type of paving is usually 2-3 inches is depth, and is the primary wear surface for the parking lot design. A self-propelled asphalt paver, sometimes referred to as a laydown machine, is used to spread the asphalt and cover up the ABC or exposed grade. Occasionally the paving is done on existing native soil, but this is not recommended for longevity.

As the asphalt is dumped in the hopper at the front of the paving machine, it is channeled back to a set of augers to spread the hot mixed asphalt in front of the screed. The screed is basically a giant free floating weight that spreads the asphalt to a desired width and depth. Once the “mix” has passed under the screed, the real work begins. It is raked and rolled to a nice smooth finish. Proper compaction is essential; otherwise there can be too many air voids in the compacted asphalt or “mat.” A combination of double steel drum and rubber tired rollers are used to achieve the correct amount of compaction.

An asphalt overlay is frequently performed as a maintenance project on a parking lot where there are some surface failures. This is a more economical alternative to re-paving an entire parking lot with a complete reconstruction, however there are a few drawbacks.

One drawback is reflective cracking. Anything underneath the pavement that is failing will eventually show through to the surface. Weather and load conditions will affect this, but generally within a year or so the cracks will be visible to some degree.  A parking lot that is completely repaved will last longer than one where an overlay has been applied.

There have been attempts by some contractors to “sell” the customers on applying a layer of geotextile fabric, as a helpmate to slow down the wear process.  However, engineering studies have shown that this is not effective. We recommend that you be leery of contactors who may attempt to “promise the world” by applying a fabric overlay. The other negative aspect to an overly is that it can cause adverse results in the drainage of the parking lot or road. Taking readings with lasers or other grade checking devices around doorways is necessary to be sure that water will be actually flow into buildings on the property.