Last week we began our discussion of different types of asphalt. The exploration began with stone-matrix asphalt, perpetual pavement, and porous asphalt. However, there are more types of asphalt to look at. Read on to learn all about the other three types of asphalt. All of the information about the different kinds of asphalt comes from the National Asphalt Pavement Association.
Thin Overlays
Thin overlays are effectively a rescue operation for an old asphalt road. Pavers come through and leave a thin layer of asphalt over the existing road. The thin overlay is made up of recycled aggregate combined with fresh asphalt. As surprising as it may be, the small sliver of asphalt extends the life of the existing road. The extension may amount to over a decade. This is primarily because the additional layer carries structural weight.
An experienced paver has the ability to get the thin overlay to a depth of only 5/8 of an inch. The low amount of asphalt in use also increases how cost effective the thin overlay asphalt is. In fact, the price can go as low as 25 cents per square yard.
Warm-Mix Asphalt
Warm-mix asphalt has many subcategories, so the term should be viewed more as an umbrella term than something specific. Usually asphalt is a hot-mix substance and is poured while hot. Warm-mix asphalt technologies allow contractors to use the asphalt when it is approximately 50 to 100 degrees cooler than hot-mix standards. The dramatic decrease in temperature offers a few major benefits for asphalt pavers as well as the general public.
- Reduction in fuel consumption.
- Lesser environmental impact by lowering greenhouse gas emissions and increasing recyclability.
- Other construction benefits, such as ability to pave at lower temperature, an extension of the paving season, and better compaction in the asphalt.
The warm-mix technology developed a little less than a decade ago and has grown rapidly over the past couple of years.
Quiet Pavement
Quiet pavement, much like warm-mix asphalt, is a general term that is more appropriately described as a category. The ultimate goal of quiet pavement is to mute the noise pollution generated by traffic, especially heavy traffic. There are two primary types of quiet pavement.
- Stone-matrix asphalt, also known as stone mastic asphalt or SMA. We discussed this type of asphalt extensively in part one.
- Open-graded friction course, also known as OGFC. This is another heavy duty asphalt mix.
Quiet pavement reduces noise pollution, on average, three to five decibels according to research done on major highways in the United States and Europe. Depending on the quality of the paving, it can be even more. That amount of noise reduction is essentially the same as doubling the distance between the listener and the noise source.