VAA Virginia Asphalt Fall/Winter 2019

20 FALL/WINTER 2019 tests. As noted above, test results are not favorable for either the Ideal-CT or the Cantabro. Superior’s initial test results indicate average Ideal-CT results ranging from 23.9–55.1 (minimum is 70) and Can- tabro results ranging from 5.9–7.8 (maxi- mum is 7.0). The VTRC has not completed all testing as of the writing of this article. Boxley Asphalt Lynchburg Pilot Effort Boxley Asphalt joined the BMD pilot effort in July of this year with a primary focus on how the use of rejuvenators would impact their standard mixes. The control mix is an SM-9.5D with 26% RAP. They produced two mixes, both based on the control mix, utilizing two different rejuvenators. Boxley joined the effort after the initial design work of the control mix was completed. Therefore there is no as-designed performance data included. As with the other pilots, both Boxley and VDOT/VTRC are performing the referenced tests. Thus far, test results are mixed with Ideal CT, and Cantabro tests passing their preset targets on aver- age. Boxley’s initial test results indicate average Ideal-CT results ranging from 99.0–216.8 (minimum is 70) and Cantabro results ranging from 5.0–5.2 (maximum is 7.0). However, there is significant variability in the Ideal-CT data. Sample fabrication and processing seems to be the primary area of concern. The VTRC has not completed all testing as of the writing of this article. Andre Royal, Boxley’s Asphalt Quality Control Manager, indicates enthusiasm for the future, saying, “It’s nice to be on the cutting edge of tomorrow’s better mixes. Boxley is proud to be a participant in the Balanced Mix Design program.” Concerns with Sample Preparation Seen in NCAT Round Robin A recent article, Preliminary Results from NCAT Performance Test Round Robin, by Adam Taylor (Assistant Research Engi- neer, NCAT), highlights a potentially significant concern with how sample preparation can impact the Ideal-CT test results. “In this phase, the between-lab mean CT Index was 103.7, the standard deviation was 11.5, and the COV was 11.1%. These results reveal how much effect sample fabrication has on variability. In the case of the Ideal-CT test, the COV was reduced from 33.3%–11.1% from Phase 1 to Phase 2, indicating that differences in sample fabrication from lab to lab contributed to two-thirds of the overall between lab variability of the test. This is an important finding that emphasizes the need for thorough hands-on training as part of implementation plans for perfor- mance tests used in mix design or produc- tion testing.” This concern is validated with much of the testing performed to date during the pilot effort. While not reported here, to date, there is significant variability in Ideal-CT results (both in-lab and between-lab). A future focus on sam- ple fabrication and processing is necessary. Concerns with Pine Press During this initial phase of Virginia’s pilot effort, information became available from Pine Test Equipment, indicating that the Pine 850T Test Press did not meet the requirements for ASTM D8225-19 (the Ideal-CT test procedure). The issue stemmed from whether or not the Pine 850T maintained a consistent 50 ± 2 mm/ min for the entire test. There are generally two types of presses used for this testing, a servo-hydraulic machine (a.k.a Testquip, now distributed by Troxler) and the screw- type machine as produced by Pine. Since that time, some effort has been made to determine the true impact of this issue. Pre- liminary results indicate that while the Pine Press does not meet the load rate require- ment set forth in ASTM D8225-19, there is likely no statistically significant difference between the two types of machines. Cer- tainly, there is more information to come on this issue. While this issue has not directly impacted the data collected to date, it is one that is being followed closely. Conclusions If you solely looked at the initial effort from Superior Paving Corp’s Bull Run facility, you could easy conclude that there are no issues with meeting the performance requirements. In fact, there was a discussion as to whether or not the targets were set too low. Yet, as can be seen following the efforts from Superior Paving’s Powell Lane facility and Boxley’s Lynchburg facility, it is clear that there is much left to learn. This is a multi-year pilot effort that will certainly require many adjustments along the way. As testing and trials continue, Virginia will continue to be a leader in the field of Bal- ance Mix Design. △ continued from page 18 FINDING THE RIGHT BALANCE Boxley - Lynchburg Mix Ideal-CT Cantabro SM-9.5D Design Production Design Production 26% RAP Control N/A 99 N/A 5.1 Rejuvenator 1 N/A 216.8 N/A 5.2 Rejuvenator 2 N/A 156.1 N/A 5 Superior Paving Corp - Powell Lane Mix Ideal-CT Cantabro SM-9.5D Design Production Design Production 30% RAP Control 38.2 N/A 5.9 N/A 40% RAP PG64-22 23.9 N/A 7.4 N/A 40% RAP Rejuvenator A 45.9 N/A 7.5 N/A 40% RAP Rejuvenator B 55.1 N/A 7.8 N/A 40% RAP Rejuvenator C 50.7 N/A “ “ N/A