Complex modulus and fatigue behavior are important characteristics for all materials. Some European countries have developed performance oriented requirements for bituminous mixtures. Using such requirements it is expected that the life of pavements can be improved. According to the European standards, these properties are characterized by various methods including two point bending (2PB) on trapezoidal specimen and four point bending (4PB) on prismatic specimen. It is known that the fatigue results obtained are highly dependent, in addition to the mixture variables and environmental variables, on specimen fabrication procedure and test equipment and procedure. Therefore the question remains how comparable are the results obtained from these tests? Up to date, a significant amount of data on comparison of the results of such tests is absent. This paper presents results of a Swiss inter-laboratory study on 2PB and 4PB tests for complex modulus and fatigue conducted on a wide pallet of specimen produced from aged field sections. The results show that a good linear regression for complex modulus values were obtained, however, the fatigue performance ranking obtained from the two tests were dissimilar.
The amount of heavy traffic is increasing continuously asking for high performance road pavements. The higher requirements in terms of stability and fatigue behavior are the main reason for the elevated use of polymer-modified bitumen (PmB). Despite the fact that PmB have been known and used for several decades, standardization is still inadequate in some parts. Only in 2012, the standards for binder extraction and has been adapted to PmB. Still, binder results obtained by the extraction with different solvents are often questioned. In this study binder extraction and recovery was investigated in detail for five PmB available on the Swiss market and four different solvents (toluene, xylene, dichloromethane, tetrachloroethylene) from the list suggested by the European standard EN 12697-3 for binder recovery by distillation. In a first step, only the recovery process of dissolved binders was evaluated. The differences measured between virgin and recovered PmB were remarkably small for most binder and solvent combinations. In a second step, the extraction process was verified on a semi-dense asphalt concrete. Again, in most cases the properties of recovered binders showed little difference concerning penetration and elastic recovery for all four solvents. Only for some binder/solvent combinations problems were detected, in particular with dichloromethane. Examination of the residual solvent by gel permeation chromatography (GPC) showed solvent residues of lower than 0.2% by mass in the case of toluene and slightly higher residues for xylene and tetrachloroethylene. The study of the micromorphology of polymers carried out by fluorescent microscopy revealed, with the exception of one binder, little effect on the distribution and restructuring of the polymers in the bitumen. In conclusion, it can be confirmed that the standardized extraction and recovery method works well for most cases with only small deviations from the original values. However, there are binder/solvent combinations where the extraction is not possible or where large differences between recovered and virgin binder are encountered for some rheological tests.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.