Koriuk V. Substantiation and development of the laboratory method of asphalt-concrete mixtures compaction by rolling

The thesis is devoted to the development of the method of laboratory compaction of asphalt-concrete mixtures by rolling. In work the analysis of existing laboratory and industrial methods of consolidation of asphalt-concrete mix is provided. It is shown that the most common method of compacting layers of pavement is the method of rolling by road smooth-roller wheels. In the laboratory, the compaction is carried out using a hydraulic press with a pressure of 30 MPa or 40 MPa. Thus, the results of the physical and mechanical properties of asphalt concretes, compacted in the laboratory and at the production site, can differ due to different compaction schemes. Therefore, the use of compaction of laboratory slabs with a sector press as an analog of industrial rolling has been suggested. The distribution of properties along the compaction plate is studied. It is shown that the maximum high properties of asphalt concrete samples are concentrated in the center of the compacted plate. It was found that the distribution of properties over the height of the sample is different and, as the layer deepens into the layer, the properties deteriorate, which agrees with the samples taken from the coating. The rate of crushing stone material was established. The mixture of stone materials was sealed with a predetermined number of passes and line pressures of the sector press. Linear pressure was defined as the ratio of the mass acting on the sector roller to its length. The contents of the mold were scattered on control sieves 5 and 10 mm. The residues on the sieves were weighed and compared with the initial mass. Also, the rock material crushing index was established when the mixture was compacted with a pressure of 30 MPa. The result obtained as a result of the inspection showed that the granularity of stone materials is higher for pressing than for rolling twice (28% versus 12%). However, it was found that the introduction of bitumen into the mineral mixture reduces the granularity of the stone material. In this work, we observed the movement of grains of crushed stone when compacting mixtures by rolling and pressing. The observation was carried out through a window cut in the side part of the mold by means of a camera. Recorded video, after each pass cut into slides and traced out the contours of the «labeled» grains and at the control point the contours were superimposed on each other. As a result of superposition, the trajectory of the grain transfer was determined. So the vertical movement of grains during rolling is higher than the vertical movement of grains during compaction by pressure. along the vertical displacement when rolling the mixture by the sector there are horizontal movements, which are 10 times smaller than vertical ones. When compressing the mixture by pressure, the vertical movement of the grains does not exceed 5 mm and horizontal displacements are practically absent. This indicates that a greater density of coagulated mixtures is achieved by greater mobility of the mineral part. The effectiveness of the method is proved by the results of comparison of the strength and water saturation indexes of asphalt concretes compacted in the road with compactors and asphaltic concrete from the same mixtures that were reformed by the sector press. The practical application of the method of compaction of asphalt-concrete mixtures by rolling, will allow to predict the properties of asphalt concrete in calculation of its composition more objectively than in the case of pressure compaction, to design the optimum binder content in it, to control the industrial compaction of asphalt-concrete mixtures. The results of the research were taken as the basis for SOU 42.1-37641918-092:2014 «Method for determining the minimum acceptable sealing temperatures» and sealing methods included in DSTU B V.2.7-319:2016 «Asphalt mixtures and road and airfield asphalt concrete. Test methods». The proposed method of compaction is used in certification tests of felling when controlling the quality of sealing coatings on roads in Kharkov.