Book Description
In recent years, a group of technologies has been introduced in the United States that allows producing asphalt mixtures at temperatures 30 to 100oF lower than what is used in traditional hot mix asphalt (HMA). This group of technologies is commonly referred to as Warm Mix Asphalt (WMA). From among these technologies, foamed WMA produced by water injection has gained increased attention from the asphalt paving industry in Ohio since it does not require the use of costly additives. This study evaluated the low-temperature performance of foamed WMA and compared it to traditional HMA. Two asphalt binders (PG 70-22 and PG 64-28), two aggregate types (limestone and crushed gravel), and two aggregate gradations (12.5 mm NMAS and 19.0 mm NMAS) were used in this study. The low-temperature behavior of the asphalt mixtures was evaluated using the thermal stress restrained specimen test (TSRST). In addition, the low-temperature properties of the asphalt binders were measured using the bending beam rheometer (BBR). This allowed for comparing the fracture temperature obtained from the TSRST to the low-temperature performance grade obtained using the BBR test.In general, the foamed WMA mixtures exhibited warmer fracture temperatures and lower fracture stresses in the TSRST than the traditional HMA mixtures. This indicates that the HMA mixtures have better resistance to low-temperature cracking. It was found that the binder grade had the most significant effect on the fracture temperature followed by the mix type, while the aggregate type had the most significant effect on the fracture stress followed by the binder grade and the mix type. The fracture temperatures measured in the TSRST were also found to be consistent with the low-temperature performance grades obtained using the BBR test.
