Analysis of the fractional composition of the stone filler in the asphalt concrete mixture and evaluation of the preparation modes for the 'bitumen–mineral powder' binder system

Introduction. The fractional composition of the stone filler in asphalt concrete mixtures and the preparation modes of the binder in the "bitumen – mineral powder" system have a significant impact on the performance characteristics of asphalt concrete mixtures. Considering that the filler volume of asphalt concrete mixtures reaches 96% by weight or 87% by volume of the mixture, and the binder volume is up to 4% by weight or up to 13% by volume. During the preparation of the asphalt concrete mixture, efforts are made to achieve its homogeneity and ensure complete coverage of the filler with binder. However, a lack of binder leaves voids, which lead to increased water absorption. Materials and methods. Based on optical studies of the fractional composition of a standard asphalt concrete mixture, the areas of interphase interaction between the stone filler and bitumen were determined, consistent with the results of other researchers. Based on the analysis of experimental and theoretical studies, the dependences of the interaction coefficient in the "bitumen – mineral powder" system on the dispersion composition, temperature, and filling degree were established. Results and discussion. Analysis of the obtained data proves that the interaction between bitumen and mineral powder follows certain patterns and depends on the volumetric particle size distribution within the mineral powder fractions, which determines the interfacial surface area of interaction. The optimal conditions for mixing temperature and composition filling are: temperature from 160 °C to 170 °C, volume fraction of 0.17–0.2. Conclusion. The selected asphalt concrete mixture formulation, which was studied in this study and contains a volume fraction of micropowder at the level of 0.258, must be adjusted upwards by increasing the bitumen mass to 2.0 kg in order to achieve the optimum interaction between mineral powder and bitumen. The obtained results allow for adjustments to the asphalt concrete mixture composition in order to improve its performance characteristics.