Chemical modification of bitumen with novel isocyanate-based additive to enhance asphalt performance

Increasing traffic loads, as well as changing climatic conditions generate the need for high performing flexible pavements, able to endure these new conditions. In recent years, many additives have been developed to make asphalt pavements last longer, preventing the typical asphalt distresses such as rutting, thermal cracking and fatigue cracking. In this investigation, a novel liquid, low-viscous chemical additive (B2Last®) is presented for its use in asphalt binders. Special emphasis was set on the modification procedure, where two different methods were studied: a batch modification and an in-line modification, both on a laboratory level. The isocyanate-based additive modification could be successfully followed with the help of attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) measurements. This technique allowed to identify specific functionalities and to follow the curing of the asphalt binder with the isocyanate-based additive until the completion of the reaction. Additionally, a comprehensive analysis, including conventional and rheological asphalt binder tests, was performed on different asphalt binder samples with 2,0% by wt. of additive. The results obtained from the mechanical properties show a clear increase in the stability against rutting, without affecting the low temperature behaviour. Moreover, the latter was supported with the analysis on the parameters of the 2S2P1D model. The isocyanate-based additive proved to enhance the asphalt performance.