When new pavement surfaces are sought after for your property – there are two options to consider: Asphalt Re-construction or an Asphalt Overlay.
In this article we will discuss the differences, pros and cons of each, and some facts relating to them that will help the reader not only understand more, but help them make educated and informed decisions.
Asphalt Re-Construction involves the complete removal of existing asphalt down to the base course. This option is highly recommended when the current condition is beyond repair – for example, there is more repair to do than areas that are in good shape. The steps involved to achieve a well done asphalt re-construction the following steps should be followed:
- The first step is to remove all of the existing asphalt down to the base course with either the use of a cold planer or tearing it out in chunks.
- Cold planers definitely make for a better efficient job. They make a recyclable product (RAP) that can be re-used for many purposes such as base course or put back into asphalt during production – most asphalt product made today has anywhere from 18 to 20% RAP in it. Not many smaller paving contractors own a cold planer due to their high point of entry for cost.
- Chunks tend to be cumbersome and difficult to get rid of. In addition, it takes more trucks to move the material – it does not load as tightly as RAP from a cold planer.
- Once down to the base course, the contractor needs to assess the base course – sometimes new base course needs to be added, or areas such as soft spots with mud need to be removed and replaced – then re-graded and compacted.
- Next, SS-1H tack coat needs to put down to help with adhesion.
- Now the contractor is ready to pave. The industry standard for new asphalt is a minimum of 2” thick – sometimes you will encounter the project requires 3” or 4” thick asphalt. This is due to a heavy traffic situation where large trucks such as garbage trucks, semi-tractors, or forklifts are common and used daily over the asphalt. Please note: when paving at 4” or thicker is being done, it needs to be done in 2 lifts to achieve proper compaction.
The great thing about an asphalt re-construction is that you end up with a brand new great looking parking lot that will have a long life of 18 – 20+ plus years – even longer with a proper maintenance program (please refer to our article we wrote for BMH – December 2013 issue for highly effective maintenance programs)
The downside to an asphalt re-construction is that it tends to be more expensive than an overlay, unless the overlay project has so many areas to correct – then the tables reverse and the re-construction is the more logical choice. Your normal asphalt re-construction can range from $3.95 psf to $5.00 psf or more while an overlay ranges from $2.50 psf to $3.35 psf.
Asphalt Overlay is the process of placing new asphalt over existing asphalt. We normally only suggest this method when the existing asphalt is in decent shape – no heavy cracking or deteriation of binder. The steps to achieve a good overlay are as follows:
- Clean and prep the area to be over-layed by thoroughly cleaning the area with sweeping, washing, and/or blowing it free of all debris such as rocks, dirt, leaves, etc.
- Apply a uniform coat of SS-1H tack coat – this will ensure proper adhesion of the new mat. This is a must!! Many below standard contractors try to fool people by not doing this or by using seal coat instead of SS-1H tack coat.
- Pave the overlay asphalt material at 1 ½” thick or greater. Important note: many contractors will try to pave at 1” sometimes even less – this is not recommended. Use fine State Mix 5 or City & County mix 4 and apply it when the material is still hot.
- Finally – compact with only the correct equipment and achieve the maximum compaction – 95% or greater. Insist that your contractor use a rubber tire roller for finishing the mat
The minimum thickness we recommend for overlay is 1 ½” thick – at this thickness the product turns out to have the ability to last much longer than the micro overlays some companies perform. Although this process sounds simple and an easy answer to new asphalt, it has issues that need to be discussed:
- If there is existing damaged asphalt, such as potholes or alligatoring – these areas will need to be cut-out and repaired prior to the overlay. Normally, there is a base failure and it also needs to be corrected as well.
- In the event, these areas are not corrected, they will fail again very shortly after the overlay and reflect right through the new mat.
- The original height of the surface will be raised. Sometimes this causes trouble with grades that were originally set for water to move out of the lot or area and now it ends up not moving out. Also, it can cause trouble for gates and doors not closing correctly.
- If there is heavy cracking in the asphalt – it needs to be corrected prior to overlay otherwise these cracks will reflect through the new mat in a short time.
Chris R. Laird is President & RME for DC Asphalt Services, Inc. He is co-owner of DC Asphalt Services, Inc. along with Dene Schnaible. The two have more than 30 years of combined experience in the Hawaii asphalt industry. Located in Campbell Industrial Park, the company performs asphalt and concrete work throughout the islands. Please visit their website at www.dcasphalthawaii.com