The next important area is the liquid AC being delivered. Several producers over the last five years have expressed concern that there was inconsistency in the liquid AC delivered from their suppliers. Until the last couple of years, it appeared just a fluke or some unknown reason that a shipment had different handling characteristics or that some of the ACs were purchased at a certain grade and type, but performed differently from one another.
Some companies had their own methods of thorough quality control (QC) and lab testing. As an experiment, they started taking samples of incoming loads. A number of them reported dramatic findings. In one area of the Midwest, the PG grade of the liquid was way off from what appeared on the bill of lading. This wasn’t true on one load—but on several. After this contractor made the issue known to the supplier and made it clear he would continue to test incoming loads, the consistency cleared up. Another contractor and mix producer in the south had a job running over 50,000 tons of mix on a major highway project. About three weeks after both the eastbound and westbound lanes were paved, one side of the highway was gray and the other black.
Upon further investigation, it seemed like they had used different AC suppliers for each set of lanes. Even though they were “delivered the same” AC from the two suppliers, the materials performed differently. They learned that one liquid had a high percentage of re-refined engine oil bottoms (REOB). Another representative of a large asphalt producing company stated that he found the state of Florida actually allows (it is in the specification) up to 8 percent REOB.
After some unannounced testing, this contractor found that some of the liquid AC had 12 percent REOB, some 18 percent, and some over 22 percent. Therefore, listening to the contractors and various situations on these projects, Stansteel/Hotmix Parts now supplies a PG-verifying sampling station. The AC Verification Station™ is placed on all inbound material lines between the unloading pump and the AC tanks. It’s developed similarly to the Stansteel Safe-T-Station™ so liquid AC samples can be taken in a safe manner to verify either every load, or at least randomly. This becomes more important with the multiple grades of AC that many government agencies are calling for. Over the last couple of years, there have been states that have in their material of mix design formulas 11 different PG grades of asphalt. It seems like a lot, but that is what that agency has decided. We’ve also had reports that it is not uncommon to have a PG88-22 and, in a couple of cases, there have been specified a PG98-22.
The need for the device is greater than ever and there could be a significant financial impact for the hot mix producer if he’s not providing the right liquid and other ingredients.