The effect of freeze-thaw cycle on the low-temperature properties of asphalt fine aggregate matrix utilizing bending beam rheometer

- FAM samples can capture the gradation differences of fine aggregate.
- BBR is effective to determine the optimal material preparation of FAM.
- More tiny air voids in FAM cause more serious moisture damage.
- The effect of freeze-thaw cycle becomes obvious as temperature rises.

Low-temperature cracking is one of main distresses in asphalt pavements and found to usually occur within fine aggregate matrix (FAM) from the perspective of meso-scale. In this study, the Bending Beam Rheometer was utilized to investigate the low-temperature properties of FAM. Temperature, gradation, asphalt content, and gyration level were designed to be variables included in the BBR test for FAM beams. Absorption, stiffness, and m-value were selected to be evaluation indexes to explore the effect of freeze-thaw cycle. Results show that the virgin beams in FAM I-2 are less likely to crack due to the smallest thermal stress and the largest relaxation rate. Poor and rich asphalt content as well as low- and over-compaction are demonstrated to degrade the freeze-thaw resistance of FAM. The absorption indicates that more air voids in FAM result in more moisture damage, and this trend becomes more significant as the bath temperature goes up. It could be concluded that the BBR is an effective tool to predict and control the cracking possibility of FAM. The tiny air voids lead to greater heaving pressure in FAM, which is remarked as the damage mechanism behind the freeze-thaw action. Warm climate and long-lasting heavy traffic are found to be adverse factors deteriorating the resistance of FAM in seasonally frozen regions.