Peculiarities of assessing bituminous binders adhe-sion to crushed stone

Problem. An important factor in ensuring the durability and reliable quality of asphalt pavements is a high level of adhesion of bituminous binders to the surface of aggregates. At present, three methods for determining the adhesion of bituminous binders are used in the road industry of Ukraine, of which the most common is the method for determining the adhesion to crushed stone according to DSTU 8787. Goal. The aim of the work is to determine the factors that affect the accuracy and reproducibility of the results of determining the adhesion of bitumen binders to crushed stone according to DSTU 8787 and to develop methods to improve the accuracy of the results. Methodology.To achieve this goal, we determined the adhesion of bitumen of different grades to particles of crushed stone of different sizes and mineralogical composition extracted from one deposit. Results. There are uncertainties in the methodology for determining the adhesion to crushed stone that significantly affect the accuracy of the results obtained. There are certain doubts about the criteria for selecting crushed stone particles for testing, the need to take into account their size and mineralogical composition. Based on the experimental data obtained, it was found that bitumen binder films of different thicknesses are formed on particles of stone material of different sizes, which, in turn, affects the results of adhesion – with an increase in the size of the crushed stone particle, i.e., with a decrease in the thickness of the bitumen film, a decrease in the adhesion values is observed. The second factor affecting the accuracy of determining the adhesion of crushed stone is the lack of requirements in the methodology for taking into account the mineralogical composition of the particles. Practical value. Based on the experimental data, it is recommended to introduce a number of additions to the text of DSTU 8787: it is advisable to select crushed stone particles for testing not by their size, but by weight, which will reduce the effect of the thickness of the bitumen film on the results obtained; selection of particles should be carried out in a wet state; for testing, it is necessary to select particles with an average mineralogical composition characteristic of the stone materials of the deposit. Taking into account the above provisions the accuracy of the results obtained will be improved.