Structure formation in asphalt concrete when using mineral dust with high specific surface area

The increase of transport load on motorway structures requires the development of new, effective, time-stable materials for the arrangement of motorway pavements. Currently, asphalt concrete is used for pavements. Development of new asphalt concrete compositions is possible based on the analysis of structure-forming processes, understanding on what conditions the increase of physical and mechanical characteristics will occur. The authors have developed a theory of mineral dust interaction with high specific surface area with bitumen. It is established that surface layer capillaries on mineral dust grains are capable to create selective oils absorption from bitumen that will allow to create more durable asphaltenes films and to reduce thermal ageing speed of bitumen at the expense of oils cupping in a surface layer of mineral dust. The paper presents the study results of the chrysotile-asbestos surface structure. The data on thermal stability of bitumen and asphalt concrete were obtained by the simultaneous thermal analysis method with joint use of thermogravimetric. On the example of chrysotile-asbestos fibres having high specific surface area it is shown that at the temperature change section from 35 to 400ºC the mass loss of bitumen sample with chrysotile-asbestos fibres is 2,8 times less. The paper shows that chrysotile-asbestos fibres create conditions for bitumen oils preservation in asphalt concrete structure. The retention capacity is based on selective filtration (absorption) by the surface layer of mineral grains of bitumen oils.