mix it up
Modifier Performs from Lab to Field A
An innovative asphalt binder modification additive from BASF, Wyandotte, Michigan, has completed its preliminary field-testing stages with promising results.
IN THE FIELD
BASF recently finished preliminary field testing of its new additive, B2Last®, a low-viscosity liquid asphalt modification additive used to improve adhesion performance of an asphalt mix. The field tests were performed on job sites across Kentucky where B2Last modifier was added to the standard asphalt binder. All other components—gradation, asphalt content, placement—remained the same. Blankenship Asphalt Tech and Training (BATT), a consulting engineering company in Richmond, Kentucky, was on site to monitor and sample the demo projects. Participants had some positive things to say about working with the new material. One of the first real tests of a new mix, according to Phil Blankenship, owner/founder of BATT, is what it does when the truck bed is raised. “It is important with any new material to pave well and stick together,” Blankenship said. “So, when I watch the first truck raise its bed and dump the mix, I watch for these indicators: does it release well from the bed, flow through the paver, set up under the screed, workable with tools, and finally compact well. I even like to grab a sample immediately and place on the side of the road to let cool. I then observe the mix as it cools to understand what we are dealing with concerning adhesion and workability.” Another interesting characteristic of the B2Last additive is that it did not initially perform like a traditional polymer when placed on the road during the field testing. Blankenship reported that the mix came out of the truck smoothly with no sticking issues at 320 degrees F. Blankenship added, “We were working around 320 degrees F.” He said he could not
10 // October 2020
tell that there was any modifier in the mix, but when the mix cooled and set up, he was impressed with the adhesion aspect of the mix. The B2Last modifier added something that he referred to as “toughness.” “I could not feel any stickiness until the mix began to cool after rolling,” he said. “I then went back to the pile that I had made on the roadside. While you can normally pick off aggregates from a typical mix, I could not get a stone to move. B2Last is extremely adhesive tough.” Zack McKay, laboratory operations manager for BATT, was also on site and had several observations. “Some of the immediate feedback I received was that it didn’t have that traditional asphalt smell,” McKay said. “It removed the odor of the asphalt.” During the field-testing stage, paving crews worked with a B2Last-modified mix and a non-modified mix for comparison purposes. The paving crew found a significant handling difference between the two as well. “When we transitioned to the B2Last binder, the paver operator to the crew working the back of the screed and the roller operator, all commented there was a noticeable difference,” McKay said. “All said it was a more workable mix to handle than the non-modified mix that we had started with.”
IN THE LAB Working with B2Last, similar results were seen in the lab. McKay tested materials sampled from the Kentucky field trials that compared the B2Last-modified mixes to the non-modified mixes. “While working with mixture in the lab, we saw that samples required less gyratory compactive effort than its non-modified counterpart [standard mix],” he said. “The repeatability we have seen in this trend may indicate that B2Last enhances compactibility.” Further studies into compactibility of the B2Last mixture are on the horizon at the BATT lab by analyzing the laboratory-pre-
One of the first real tests of a new mix, according to Phil Blankenship, owner/founder of BATT, is what it does when the truck bed is raised. Blankenship reported that the B2Lastmodified mix came out of the truck smoothly with no sticking issues at 320 degrees F. pared and plant-produced mixtures with non-modified mixtures. The IDEAL-CT (ASTM 8225) testing also showed positive results with the B2Last-modified mixes. “When we compared the Kentucky non-modified mixture to the modified mixture, we saw an improvement on the resistance to cracking,” McKay said. “B2Last test mix provided a higher CT index value, and those higher values are an indicator of better cracking resistance. This indicates a reduction in cracking pavement over time [as compared to the standard mix].” Further study at the BATT lab included evaluating a standard mix and comparing it to a B2Last-modified mix with the same job mix formula (JMF). Blankenship commented, “It is exciting to see how new materials perform in the lab. While materials can do well in the field, our testing is not always robust enough to pick up on performance characteristics of new materials. This means we have to keep our lab-eyes wide open and not just ‘run the test.’” “We conducted testing on formulations of B2Last with SBS polymer modified binders and compared it to a KY standard [3/8-inch NMAS surface] control mixture,” McKay said.
