The consideration of air void content effect on asphalt concrete elastic modulus in pavement design

Introduction. It has been demonstrated that air voids are inherently structural defects in asphalt concrete. The article presents information on mathematical models that take into account the influence of air void content on both the elastic modulus of asphalt concrete and the service life of the pavement, expressed as the cumulative number of design loads that the pavement can withstand before failure. Therefore, considering air void content when determining the elastic modulus of asphalt concrete used in pavement design is a relevant and practically significant task. Materials and methods. The analysis of methods for accounting the damage accumulation effect applied to the fatigue destruction resistance calculation of asphalt concrete and other materials has been performed. Relying on this analysis, it was concluded that the damage theory can be used to determine the elastic modulus of asphalt concrete. The analogy between Yu. N. Rabotnov’s damage parameter and air void content is emphasized. Furthermore, the possibility of applying the principle of deformational equivalence between a damaged and a homogeneous medium to the calculation of asphalt concrete elastic modulus is justified. The concept proposed by L.M. Kachanov, which involves an increase in stress magnitude with an increasing number of damages, was applied to the calculation of tensile stress in bending. Results . The results of calculating the elastic moduli of bitumen-based asphalt concrete (grades BND) with varying air void content, but within the limits permitted by GOST R 58406.2-2020, have been presented. This let the authors to supplement the data on elastic modulus values for asphalt concretes in GOST R 71404-2024. The reason to add the data in GOST R 71404-2024 is explained by the fact that the temperature of the asphalt concrete mix in different parts of the dump truck body varies, which leads to different compaction conditions for the mix based on its temperature. In this case, tests of cores taken from sampling points located close to each other show almost identical bitumen contents, but different air void contents. Therefore, when designing flexible road surfaces, it is necessary to focus on the elastic moduli of asphalt concrete that correspond to the maximum limits for the content of air voids. Conclusion. The obtained results allow to make more detailed pavement design calculations.