Abstract
Warm mix asphalt (WMA) has been widely accepted as a future asphalt paving technology. Besides clear advantages, there are still some concerns regarding durability and long-term performance of pavements made with this type of asphalt mixtures. One of the most important issues is low temperature behaviour of WMA because certain additives used for temperature reduction can affect bitumen properties. This paper presents the evaluation of low-temperature properties of laboratory-produced asphalt concrete for wearing course with selected WMA additives. One type of bitumen with paving grade 50/70 and five WMA additives of different nature (organic, surface tension reducer and combination of both) were used in this study. The production and compaction temperature of mixtures containing WMA additives was 25 °C lower in comparison with the temperature of the reference mix. To assess the susceptibility of WMA to low-temperature cracking, Semi-Circular Bending (SCB) and Thermal Stress Restrained Specimen Test (TSRST) were used. Supplementary rating was made by analysing Bending Beam Rheometer (BBR) test results of asphalt binders.
Highlights
For two wax-based Warm mix asphalt (WMA) additives, the highest values of σcry, failure and σcry, @−20 ◦ C were obtained while, for the rest of the additives, it can be assumed that stresses during fracture and at the temperature of −20 ◦ C were mostly unchanged in comparison with a reference mixture produced with the neat 50/70 binder
A similar correlation could be formulated for failure temperature Tfailure and tangent point (Tg) point that were highest for the Sasobit wax-based WMA additive
It should be noted that clear changes of bitumen properties, which shifted the binder with both wax-based WMA additives to the level of the Performance Grade (PG) grade did not affect behaviour of asphalt mixtures to the same extent
Summary
Warm mix asphalt technology is continuously gaining bigger share in total production volume of asphalt mixtures. There are several different technologies of reducing asphalt mixture working temperatures. These can be divided into three major groups: organic additives, chemical additives, and foaming technologies based on zeolite minerals or direct water injection into the binder stream with the use of plant-based systems [4]. Research efforts concerning warm mix asphalt additives are considered to be still when actual and new additives are being proposed [8,9,10,11,12,13] or combined with other substances [14,15,16] to achieve a higher degree of asphalt mixture sustainability
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