Selective sorption in filler-bitumen systems

Factors affecting selective sorption in the bitumen-filler interface and the difference in the capacity of various fillers for selective sorption of the chemical groups combining the bitumen are investigated and described. The effect, in this respect, of the type of diluent, the environmental conditions and the experimental methods are also studied.Quantitative evaluation of selective sorption was made using a chromatographic method, by percolation of diluted bitumen through columns of different types of filler. Among the fillers investigated, hydrated lime and limestone were the most effective, basalt was intermediate, while sandstone and mainly glass beads showed almost no capacity for selective sorption. In addition, the changes in the composition of the chemical groups, while percolating bitumen through a hydrated lime layer, were investigated and reported in this paper.The evaluation of selective sorption capacity of the filler is of great importance in bituminous mixture technology. Since the filler constitutes the ingredient with the highest specific surface in the granular mass of the bituminous mixture, its surface activity properties influence the mechanical properties of the bitumen-filler system and the behaviour of the mixture. Therefore, the capacity of selective sorption can serve as an indication to the future effect of the filler on the aggregate-bitumen-filler adhesion and the stability and deformability of the bituminous mixture. In this respect, the behaviour of sand asphalt mixtures with different types of filler was studied. Actual results were in agreement with the behaviour of the different fillers under selective sorption.