Introduction. The article investigates the effect of the preparation temperature, the amount of energy-saving additive and the amount of asphalt crumb on the physical and mechanical properties of warm asphalt mixtures. The method of experimental and statistical modeling was used in the study, and mathematical models describing the dependence of water saturation and compressive strength of asphalt concrete were developed. Based on the analysis of the results obtained, the areas of optimal values of the preparation temperature, the amount of energy-saving additive, and the amount of asphalt crumb during the production of warm asphalt mixtures were determined. In this case, the resulting mixture meets the standard requirements for hot fine-grained asphalt mixtures in terms of physical and mechanical properties.
Problem statement. Studies by the authors of [1] have shown that when preparing an asphalt mixture, it is very important to take into account changes in the properties of bitumen, which is the main component that characterizes the behavior of asphalt concrete. In the preparation of warm asphalt mixtures, it is advisable to use energy-saving additives, the introduction of which provides relatively new chemical effects that improve the workability, mobility and energy saving of mixtures made at lower temperatures than traditional hot mixtures.
At the same time, due to the large number of different types of additives, there is no accurate quantitative data on the dependence of asphalt concrete properties on the content of additives at different amounts of bitumen for different types of asphalt mixtures.
Given the high market value of additives, it is important to determine their optimal amount depending on the bitumen content, at which the set of physical and mechanical properties of asphalt concrete will be the best.
Another important factor in the technological process is the temperature of the mixture.
The authors of [2, 3] established the effect of the mixing temperature on the homogeneity of the mixture. The studies showed that an increase in the homogeneity of the mixture is achieved by increasing the heating temperature.
However, the study of the temperature limits for the preparation of warm asphalt mixtures does not provide full information on the optimal temperature conditions, since the temperature range is quite wide ― (120 – 160) °C.
Another important factor affecting the quality of asphalt concrete is the amount of asphalt crumb added to the mixture.
Asphalt crumb is added to the mixture, which is cold and wet, and which affects the production temperature and the grading composition of the mixture. In the manufacture of warm asphalt mixtures with the addition of asphalt crumb, it is necessary to take into account the quality of the crumb, namely its grading and the amount of bitumen.
Objective. The aim of the study was to investigate the effect of the preparation temperature, the amount of energy-saving additive, and the amount of asphalt crumb on the physical and mechanical properties of warm asphalt mixtures. To establish the region of optimal values of the determined factors.
Materials and methods. Experimental comparative tests of warm asphalt mixtures made at different temperatures with different contents of energy-saving additives and different amounts of asphalt crumb were carried out. The method of experimental and statistical modeling was used in the research, and mathematical models were developed that describe the dependence of water saturation and compressive strength of asphalt concrete on the preparation temperature, energy-saving additive content, and amount of asphalt crumb.
Results. The areas of optimal values of the accepted variation factors: production temperature, energy-saving additive content, and the amount of added asphalt crumb during the preparation of warm asphalt mixtures were determined.
Conclusions. As a result of the application of the method of experimental and statistical modeling, the optimal interval of technological temperatures for the production of warm asphalt mixtures, the optimal content of energy-saving additives, and the optimal amount of asphalt crumb were determined, at which the maximum values of the complex of physical and technical parameters of asphalt concrete are achieved.
