VAA Virginia Asphalt Fall/Winter 2020

34 FALL/WINTER 2020 OVEN CORRECTION FACTORS VDOT retrieves asphalt samples from the producer to calculate the same parameters. These are part of the Department’s Indepen- dent Assurance program and Verification, Sampling, and Testing program under the Quality Assurance program. While not directly used for payment, VDOT and contractor test results are compared using various statistical measures to identify potential testing or materials issues. It’s All About the Ovens For years, it has been recognized that each ignition oven has a unique influence on the OCF. As reported in an article titled “The Importance of Asphalt Content Ignition Furnace Correction Factors” for the AASHTO re:source newsletter in October 2010, “Studies have shown that asphalt and aggregate correction factors are unique to each ignition oven, regardless of manufac- turer.” In Virginia and several other states, a single OCF is calculated for a mixture and is listed on the JMF (TL-127). This OCF will be used if the contractor has more than one oven in a lab. VDOT and other third-party labs also use this OCF as part of the Quality Assurance Program. Unlike the process outlined in AASHTO T-308, each lab and oven performing testing would not determine the actual OCF per oven. So What? The bigger question for this article is—so what? Does it really matter? It does if it results in inaccurate results and pay adjustments or limited production. Both cost the contractor money. The contractor must match their determined OCF with a specific oven if more than one oven exists in a lab. For a lab with multiple ovens, the contractor should determine the OCF for each oven. With enoughmixes burned and OCFs determined, the contractor may be able to estimate a standard offset between ovens. For VDOT and third-party labs, determin- ing an OCF for each mix for each oven would be overwhelming. During any calendar year, contractors will produce more than 100 unique mixes for VDOT to test. Using a contractor supplied OCF for each mix is much easier, but not accurate in determining an AC content. For years, it has been recognized that each ignition oven has a unique influence on the OCF. As reported in an article titled “The Importance of Asphalt Content Ignition Furnace Correction Factors,” “Studies have shown that asphalt and aggregate correction factors are unique to each ignition oven, regardless of manufacturer.” Conclusion For more than two decades, ignition ovens have played a critical role in the mix design and acceptance process. Oven Correction Factors not only impact payment, but they assist the certified asphalt mix designer in making adjustments to the asphalt plant. Contractors using more than one ignition oven are strongly encouraged to determine an OCF per mix by oven. Likewise, industry and VDOT should review the impacts of OCF on the Quality Assurance Program and determine what steps should be taken to improve the process. △ continued from page 32 FIGURE 1: Dual Ignition Ovens, Colony Construction, Inc.