Abstract
Compaction technique used in Marshall design does not model the process of actual rolling procedures on site exactly. Carrying out laboratory compaction of dense bituminous mixtures with Superpave gyratory compactors is a more realistic way of simulating actual compaction. In this study, mechanical differences of reference and polypropylene modified asphalt mixtures were compared using Superpave gyratory and Marshall compaction methods by carrying out repeated creep tests utilising universal testing machine. In addition, there is no standard Superpave design procedure for 100 mm diameter samples till date. The other purpose of this study is to propose new standards for the compaction and testing procedures of these 100 mm specimens. Indeed, extensive studies have shown that the design gyration number should be 40 for reference and 33 for polypropylene modified specimens under medium traffic conditions for the similar and specific type of aggregate sources, bitumen, aggregate gradation, mix proportioning, modification technique and laboratory conditions. Moreover, it was shown that, the asphalt samples produced by Superpave gyratory compactor were much resistant to destructive rutting effects than the asphalt specimens prepared by Marshall design.
Highlights
The creep test, for many years, has been used to estimate the rutting potential of dense bituminous mixtures
The very basic aim of this study is to investigate the rutting potential of polypropylene modified 100 mm diameter asphalt specimens prepared by using the Superpave gyratory compactor and to compare the obtained results with the previous studies of the lead author
It can be clearly be concluded that the lives of the polypropylene fiber modified asphalt specimens under repeated creep loading at different loading patterns increased by 8-18 times versus reference specimens when gyratory compaction is being utilised in the preparation of 100 mm diameter asphalt specimens
Summary
The creep test, for many years, has been used to estimate the rutting potential of dense bituminous mixtures This test is conducted by applying a static or a repeated load to an asphalt specimen and measuring the resulting permanent deformation. A further step of analyses has been carried out and the 100 mm diameter plus approximately 60 mm long specimens have been mechanically tested in order to compare their mechanical test results under repeated creep testing with the previously tested Marshall specimens under the same test temperature and loading conditions for repeatability necessities This is one of the major differences in this study of the previous literature. In order to be able to monitor the tertiary creep region of asphalt specimens under creep testing, a completely different loading pattern, loading stress level and testing temperature than the previous studies have been adopted This is the most important distinction from the published literature till date[27]. The very positive effect of gyratory compaction on the prevention of strain accumulation in the specimen bodies when compared with dynamic Marshall compaction is explored in a detailed manner
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