With VDOT marching toward balanced mix design (BMD) in the next few years, many questions must be answered. One of the biggest questions surrounds the variability of the testing. Given the same mix, how different will the results be between technicians, labs, and equipment? To start understanding that variability, VAA and VTRC have partnered to host a round robin investigating the Ideal-CT test. Using two different mixes – 9.5 mm NMAS and 12.5 mm NMAS, five gyratory pills for each mix will be supplied to participating labs and companies. Upon receipt of the pills, technicians will perform the Ideal-CT test using their equipment and report the results to VTRC. VTRC will accumulate the data, perform numerous statistical analyses, and provide a report.
A third-party lab will produce all mixes in a very controlled environment. Aggregates will be sieved to specific sizes and weights; the asphalt content will be carefully introduced and mixing performed. This procedure will remove material variability from the mixes used during the round robin.
Once this round robin is completed, future round robin efforts are envisioned to investigate the impacts of material variability and other factors on test results. To learn more about this round robin, please contact Mike Dudley.