Long-term strength of bitumen during glass transition

Abstract

Abstract. Problem. Long-term strength and durability are the most important characteristics of any structural material. Since these mechanical properties depend on their manufacturing technology and composition, there is a need to conduct research on road construction materials for long-term strength and durability. There are many studies on the long-term strength of various solids, including asphalt concrete, but there is no data on the long-term strength of bitumen, which is in a glass transition state at low temperatures. The main goal. The aim of the work was to experimentally determine the long-term strength of bitumen at low operating temperatures. It was also necessary to establish how the structural type of bitumen and its filling with various mineral powders affect long-term strength. Methodology. To determine the long-term strength of bitumen, the Heppler consistometer, which is often used in the thermomechanical analysis of polymers, was adapted. To study the influence of the structural type of bitumen on its long-term strength during glass transition, bitumens with the same penetration and close to the first (gel), second (sol) and third (sol-gel) structural types were obtained. Results. The nature of the dependences of the time to destruction from the applied load at a constant bitumen temperature differs from the similar dependences of solid single-phase materials. During the transition of bitumen to a glassy state, static destruction depends on the plasticity of the material, the greater it is, the lower the temperature stress due to the irregular complex structure of the material. Bitumens of the first structural type (gel) show better relaxation properties at low temperatures compared to bitumens of the second structural type (sol). As a result, their long-term durability is higher. Filling bitumen with mineral powders of different origins changes the structure of the binder, it becomes more ordered. The result is an increase in strength and a decrease in temperature stress of bitumen during glass transition. Originality. New experimental data on the long-term strength of bitumen at low operating temperatures were obtained. It is shown that they are described by the formula of S.M. Zhurkov. Practical value. It is possible to improve the low-temperature properties of asphalt concrete by using bitumen of the first type with quartz mineral powder