Influence of compaction direction on performance characteristics of roller-compacted HMA specimens

Abstract

Hot mix asphalt (HMA) slabs produced by roller compaction can be used to core and cut specimens for further testing. The relation between the direction of compaction and testing in the laboratory is not always the same relation as it is between the direction of compaction and actual loading in the field. This paper presents outcomes of a study analysing the influence of the compaction direction on performance characteristics of roller-compacted HMA specimens. Performance parameters of a base layer mix are obtained from performance-based test methods, including high-temperature, stiffness, fatigue and low-temperature tests. The relation between direction of compaction and specimen testing is varied in all three dimensions to find relevant influences. From the results, it can be concluded that all obtained performance parameters are sensitive to the anisotropy of the material due to compaction, especially for stiffness and fatigue performance. For the high-temperature performance, specimens from path-and force-controlled compaction were compared. The applied compaction work rather than the compaction method is linked to the difference in the corresponding results. The uniformity of the compaction in terms of the variation of bulk density of the specimens reflects on the scattering of test results.

Introducing a nitrogen conditioning to separate oxidative from non-oxidative ageing effects of hot mix asphalt

“…This is a necessary precondition since all specimens were tested twice, before and after laboratory ageing. To avoid differences in the performance characteristics due to the compaction direction (Hofko, Blab, & Alisov, 2016), the slabs were marked with lines before the specimens were cored out. All specimens were tested exactly in compaction direction both times.…”

“…• As written previously, testing the same specimen twice, before and after ageing, requires to know the possible change of the dynamic modulus |E*|. Therefore, results of specimens tested twice without ageing in between were collected in Steiner, Hofko and Blab (2016). A possible increase of |E*| was calculated with 1.05.…”