Project management
BASF, NCAT Partner for Paving Trial A low viscosity reactive liquid asphalt additive, B2Last® by BASF Corporation, was recently introduced at the 2020 Petersen Asphalt Research Conference (PARC). It is a modification technology based upon a reactive chemistry that combines with the liquid asphalt at a molecular level to improve the functional characteristics of the neat asphalt. B2Last is compatible with most liquid asphalts thus is ideal for new pavement construction and pavement preservation initiatives. B2Last is designed to increase the useful temperature interval (UTI) of the liquid asphalt, maintain workable viscosity levels, and reduce stripping of the aggregates, leading to a more durable pavement. “Functional performance improvement levels can be tailored or made ‘on-demand’ by binder formulators to meet or exceed flexible pavement specifications,” said Bernie Malonson, B2Last marketing manager, BASF Monomers, North America. “Since B2Last is a liquid, there are no solids to grind or melt, less energy is required to produce modified asphalt pavements, and it supports the American Association of State and Highway Transportation Officials (AASHTO) specifications.” While specific states vary in their authorized materials, B2Last can support both AASHTO M320 and M332 performance grade (PG) specifications. In many cases, modified asphalt producers have noted that they are able to use less B2Last and simplify their formulations. Although successful paving operations have been conducted globally, BASF has partnered with the National Center for Asphalt Technology (NCAT) in Auburn to conduct a Phase I study as part of BASF’s ongoing program of B2Last trial evaluation.
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CHEMISTRY & STUDY DESIGN
B2Last is designed to improve adhesion of the asphalt mix by crosslinking the liquid binder asphaltenes. When handled with appropriate environmental controls, B2Last modification does not require any unique personnel protective equipment (PPE). NCAT Phase I paving studies typically take six to 12 months and include a laboratory testing program to determine the mechanistic and performance properties of asphalt binders and mixtures. The core NCAT research team led by Dr. Nam Tran, assistant director, NCAT, with paving operations overseen by Dr. Buzz Powell, associate director, NCAT, and additional support provided by Jason Nelson, test track manager, and Adam Taylor, assistant research engineer, were on site for the trial. The primary objective of this Phase I study is to evaluate the field constructability of an asphalt mixture modified with B2Last. The information obtained from this study will be used for a structural pavement analysis to plan and design a full-scale experiment for placement on the Pavement Test Track in 2021 to fully evaluate the B2Last modifier.
26 // November 2020
The material was continuously mixed at 350° F until shipping to achieve full reaction within the binder. To ensure completion, a portable on-site FT-IR took hourly readings. In May of 2020, Brian Orr, senior asphalt technologist, BASF Monomers, NA, and Joshua Compeau, technical specialist, BASF Monomers, NA, traveled to Alabama to oversee liquid asphalt terminal modification. In the case of a new asphalt binder modifier such as B2Last, it is best to produce these materials at a terminal asphalt plant and then pave the mix in a trial section with low traffic. A base binder of PG67-22 was used to meet the ALDOT required grade of binder. This binder was modified with a 2 percent concentration of B2Last to reach an acceptable PG76-22. The process used to modify the binder was achieved by injecting the B2Last with a 2-inch diaphragm pump through an injection port into 50 tons of asphalt binder, which was used to ensure the binder reached an adequate level for mixing and agitation in the modification tank. After injecting the B2Last, monitors took hourly readings around the work area for any potential off gassing. The material was continuously mixed at 350° F until shipping to achieve full reaction within the binder. To ensure completion, a portable, on-site Fourier Transform Infrared Spectrometer (FT-IR) took hourly readings. “The main challenge in using reactive chemistries is to ensure that the product is allowed sufficient time to completely react within the liquid asphalt,” Orr said. “The completion of this molecular reaction is what improves the functional characteristics of the liquid asphalt.”
