Abstract
This study evaluated the low-temperature performance of foamed warmmix asphalt (WMA) produced by water injection and compared it with that of hot-mix asphalt (HMA). Two asphalt binders (PG 70–22 and PG 64–28), two aggregate types (limestone and crushed gravel), and two aggregate gradations [nominal maximum aggregate size (NMAS)] (12.5-mm NMAS and 19.0-mm NMAS) were used in this study. The low-temperature properties of the asphalt binders were measured with the bending beam rheometer, and the low-temperature behavior of the asphalt mixtures was evaluated with the thermal stress restrained specimen test after being subjected to short-term and long-term aging. As expected, the fracture temperatures obtained for the short-term aged specimens were lower than those obtained for the long-term aged specimens. This was the case for both foamed WMA and HMA mixtures. The HMA mixtures exhibited colder fracture temperatures than did the foamed WMA mixtures for the short-term aged specimens, but fracture temperatures comparable to those for the long-term aged specimens. This comparison suggests that the traditional HMA mixtures may have better resistance to low-temperature cracking than foamed WMA does during the initial service life of the asphalt layer, but may have similar resistance to low-temperature cracking at later stages. This study also showed that the low-temperature binder grade had the most significant effect on fracture temperature, whereas the aggregate type had the most significant effect on fracture stress.
Get full access to this article
View all access options for this article.