INCREASING THE EFFICIENCY OF THE BITUMEN-MINERAL MATERIALS COMPACTION PROCESS WITH A ROAD ROLLER

The final stage in the formation of the structure of the upper layer of the road surface is its compaction. Evaluation of compaction performance can be made by comparing the maximum drumside contact pressure with the tensile strength of the material to be compacted. As a result of considering the contact interaction of the roller with the layer of material, the relationship between the design parameters of the roller and the stress-strain state of the layer of the compacted material has been established. A method for evaluating the effectiveness of the use of a road roller is developed on the basis of measuring the arc length of the contact of its roller with the compacted material. For the practical implementation of the proposed methodology, a description of a device is given that allows monitoring the efficiency of the process of compaction of bitumen-mineral materials by a road roller.

Relationship Study and Primary Application between Gas Permeability and Crack State on Bridge Joint Concrete

For evaluating the crack state on solid bridge joint on site, the relationship between gas permeability and crack width of joint concrete is studied both on material and structural levels in this article. In laboratory tests, gas permeability tests on concrete samples with macrocrack are performed, the relationship between the relative gas permeability rate k/k0 and the relative variation of crack width ac is established combining with regression analysis, the fitting curve equation is . when ac increases by 1.125×10-2 mm, the gas permeability increases about 10 times compared with the initial state. In field tests, “pulse tests” are performed on bridge joint based on 3 embedded pulse probes to measure the evolution of gas permeability during bridge operation. The results show, firstly, the gas permeability of joint concrete are in the order of 10-16~10-19 m2, which indicates a good compaction performance; Secondly, an order of magnitude increase of gas permeability of one probe in different ages, or the fact that the gas permeability at one position in solid joint is obviously larger than the other positions, these phenomena indicate the existence of original defects, or the possibility of macrocrack appearance from microcracks, and the crack width increases by about 0.01 mm.