Determination of plasticity of mastic asphalt mixtures by the Luer method

Problem. Mastic asphalt mixtures, unlike other types of asphalt concrete, have certain granulometric and technological features that necessitate the use of specific quality indicators. The most informative quality indicators for mastic mixtures are plasticity at service and process temperatures. Unlike the service plasticity indicator, which is widely used and standardized in most countries of the world, technological plasticity, despite its importance, is of limited use for assessing the quality of mastic mixtures. Goal. The aim of this work was to establish the possibility and feasibility of using the Luer method to assess the technological plasticity of mastic asphalt mixtures in the road industry of Ukraine. To achieve this goal, an appropriate device was manufactured and the experimental study of the plasticity of mastic asphalt mixtures using the Luer method was carried out. Methodology. The determination of plasticity by the Luer method consisted of immersing a metal rod with a hammer under its own weight in the mastic asphalt concrete mixture. The Luer yield strength is the time, with an accuracy of 1 s, during which the rod with a hammer is immersed in the mastic asphalt concrete mixture at a distance of 50 mm (from the lower to the upper mark). Experimental determination of the plasticity of mastic asphalt mixtures of different particle size distribution with different bitumen content was carried out. Results. On the basis of experimental data, the sensitivity of the Luer method to the particle size distribution of mastic asphalt mixtures and the amount of bitumen in the mixture was confirmed. During the experimental verification of the Luer method, its advantages and disadvantages were identified. The advantages include simplicity of the device design and relative speed of the test. The disadvantages of the method are a significant volume of mastic asphalt mixture required for the test; rapid cooling of the mixture and the rod, especially in the case of determining plasticity at high process temperatures, which affects the accuracy of assessing the plasticity of mastic mixtures. Practical value. Based on a production test of determining the plasticity of mastic asphalt mixtures by the Luer method, the possibility and feasibility of its use in the domestic road industry when designing mixtures and setting technological temperatures for their preparation, which ensure the production of mastic asphalt concrete whose properties meet the requirements of national regulations, has been confirmed