Presently, in North Carolina the baghouse materials used in hot mix asphalt (HMA) are purged intermittently into the AC mixtures rather than being stored in a silo and added to the mixture as mineral filler in a uniform, controlled manner. Previous studies have shown that the volumetric properties of asphalt mixtures are greatly influenced by the source and gradation of the baghouse fines. Due to this reason, several states require contractors to waste baghouse fines. However, there are some environmental concerns with wasting the fines.
Recent research (Research Project 1999-03) suggests that baghouse fines with gradation similar to the natural and manufactured fines passing #200 sieve, seem to have a beneficial effect on the stiffness and rutting characteristics of the asphalt mix. However, this recent research did note that these mixes containing baghouse fines were susceptible, and recommended that baghouse fines be metered into the mix to create a uniform percentage throughout the mix.
This project will be a laboratory study of moisture sensitivity of asphalt mixes containing controlled percentages of baghouse fines in the amount of 0, 4, and 8-percent. Antistripping agent(s) selected in consultation with NCDOT will be used to determine their effectiveness in mitigating moisture damage. The study outcome should result in clear recommendations regarding maximum level of baghouse fines, the appropriate type and amount of antistripping agent, and any significant performance issues that are uncovered by the research team.
