All Pavements Are Created to Perform Equally, or Are They?

"Sustainability is moving ahead of testing technology," relates TransTech Systems president and CEO David Apkarian. Among a long list of products and services, TransTech Systems manufactures the Pavement Quality Indicator, a non nuclear gauge designed to measure asphalt density, temperature, and moisture content.

"The industry has the technology to perform accurate lab and field tests on asphalt made with asphalt-based shingles, crumb rubber, RAP, and steel slag, among other recycled materials," he explains. "Warm mix, however, is another story. The issue is the amount and type of additives used."

"Warm mix comes out at a lower temperature than hot mix, 230 degree F versus 300 degrees F. Because of this there is less off-gasing and it's more economical for plants to make. Warm mix is also easier to work with." All of this is good, he says, except one detail. Plants have to put additives in the warm mix to make it viscous at lower temperatures. The additives create the challenge.

"As a gauge manufacturer, we don't always know what additives are being used or what they will do to gauge readings, and we need to know what to measure and adjust accordingly to feel comfortable about the results. This is not Star Trek and we don't use tri-corders on the asphalt."

Apkarian is confident that his company and others can develop the right measuring tools for warm mix, but they need more information about the additive content and what it does to gauge readings. "Currently, we have the technology to test Double Barrel Green warm mix and other warm mixes have undergone limited successful testing, he adds. "Warm mix holds a lot of promise and is currently right for applications on secondary roads, but it's not ready for prime time on our highway systems."

Like Apkarian, Dick Reaves, North American Sales Manager for Troxler Electronic Laboratories, Inc., says that most recycled materials pose few if any challenges for current testing technology. Troxler's extensive line of testing equipment includes a wide range of nuclear moisture density gauges and PavTracker Plus, a non nuclear gauge for the field, along with gyratory compactors, asphalt ignition ovens, and nuclear asphaltcontent gauges for the lab.

"RAP, shingles, and crumb rubber don't adversely impact in-lab testing for mix design, quality assurance, or quality control," he explains. "The same can be said for most field compaction control tests. However, there may be issues with warm mix, more specifically with additives that may add water to the mix, which, may affect readings."

Time will tell, adds Apkarian. "The industry wants to make some necessary changes that will lower the costs associated with paving roads and help the environment. From a test equipment manufacturer's viewpoint, though, we need to be brought into the loop early on to ensure that current technology will get the quality-control job done, especially for all the variations of warm mix. "

The challenges are different yet similar for both the plant automation experts and test equipment manufacturers, and they begin and end with knowledge. Computers can handled the wide variety of recycled material going through a plant, if they know the makeup of the material. Lab and field test equipment can provide accurate test results, if their manufacturers have full knowledge of what's being tested. The goal is the same for all industry participants. Tomorrow's roads may not be created equally, but they will all have to meet and perform to the same high standards. ƒÞ

Specializing in the construction industry, Rod Dickens is a freelance writer based in Neenah, WI.