Extraction and recovery of polymer modified bitumen

Abstract

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.

Reclaimed Asphalt Pavement Binder Extraction and Recovery Evaluation and Their Effects on the Recycling Agent Assessment

“…The main aspects cited in the literature on solvent extraction and binder recovery were: (i) application of different types of solvents and their effects on the characteristics of the asphalt binders ( 14 – 16 , 18 , 19 ); (ii) effect of the extraction methods on the binder content determination and on the physical, rheological, and chemical properties of conventional or modified binders ( 13 , 14 , 20 – 22 ); (iii) efficiency of solvent removal from asphalt binder samples by Abson and/or rotavapor procedures, in addition to the influence of both techniques on its physical, rheological and chemical characteristics ( 1 , 13 , 17 , 20 , 23 – 25 ). Despite the common points investigated, there are still divergences among authors over the variations in the intrinsic characteristics of asphalt binder after passing through different extraction and recovery techniques.…”

“…Studies seek to evaluate the effect of the aged RAP binder on the performance of recycled asphalt mixtures and to determine the binder blend properties, especially when high levels of RAP are incorporated into the new mixtures (9,11,12). Some authors have also investigated and reported the effects that different extraction methods, types of solvents, and recovery processes have on the recovered asphalt binder properties (1,4,(13)(14)(15)(16)(17).…”