Adsorption and desorption of bitumen in toluene on mineral aggregate

A practical method has been developed to determine the adhesivity between bitumen and mineral aggregate in the presence of a solvent (toluene). The method is based on photometric measurement of the adsorption and desorption of bitumen on mineral aggregate. The development of the method and the influence of the test conditions are discussed. The results of a limited test program are given, in which two bitumens of different origin (Venezuelan and Arabian) were used in combination with four mineral fillers of different mineralogical composition. It was found that the adsorption and desorption behaviour of the bitumen/aggregate combination can be characterized based on Langmuir adsorption, and that the Langmuir isotherm provides a reasonably accurate quantitative characterization. It was also found that one of the fillers, Vulprofite, which is probably rich in quartz, and a pure quartz model ?filler?, yielded markedly different results in comparison with the other fillers used. For practical application of the method it may be necessary to reduce the 95% confidence intervals with the parameters for the characterization of the adsorption and desorption behaviour.