On Friday, May 27, 2022, a two-day international conference "The World of bitumen and PBB: Logistics and Infrastructure", dedicated to the problems and prospects of development of the Russian bitumen and polymer-bitumen binders market, ended in Yekaterinburg. The event, organized with the support of leading industry players, was attended by representatives of more than a hundred companies, as well as public associations and government regulatory agencies. Mikhail Slavutsky, Head of the Testing and Research Laboratory of ROSDORNII, Ph.D., delivered a report on methods for predicting the need for repair of asphalt concrete layers of road coverings based on the results of tests of road-building materials to the conference participants.
The expert reviewed the main existing approaches to determining the quality of road construction materials and works and clearly showed their fundamental shortcomings. In particular, there is no relationship between the quality and cost of work and, as a result, it is fundamentally impossible for the contractor to increase profits by increasing the cost of work while improving their quality.The approach developed by ROSDORNIA, which makes it possible to predict the time of the actual need for repair of asphalt concrete layers during design, will help to create additional prerequisites for improving the operational properties of asphalt concrete and increasing the repair time.
"The issue of estimating the expected actual repair time at the design stage of asphalt concrete is of particular importance for comparing options with different costs and with different properties. If there is information about an increase in the service life of a more expensive version of asphalt concrete compared to a cheaper one, it is possible to determine which of these options is more appropriate using the method of bringing different costs. Even though there are no approaches in the existing road regulatory and technical literature that allow in a strict sense to predict the actual service life of asphalt concrete pavements, it is possible to develop methods for evaluating this parameter. For example, by comparing estimates of the timing of the actual need for subsequent repairs for asphalt concrete, which showed different test results of the main consumer properties at the design stage," Mikhail Slavutsky said.
He gave a detailed description of the methodology developed at the Institute, told about the factors affecting the timing of subsequent repairs, and about the methods of their numerical evaluation. In particular, it was shown that the time of occurrence of the actual need for repair of asphalt concrete by more than 60% depends on their fatigue strength and on the compliance of the actual PG characteristics of the bitumen binder with climatic requirements and traffic conditions. At the same time, the use of higher-quality materials can significantly increase the duration of the overhaul period
As an example, the experience of assessing the compliance of the actual PG characteristics of the bitumen binder with the required one performed by ROSDORNIA in 2020-2021 for 42 subjects of the Russian Federation, during which 90 samples of PBB were examined, was given. Tests have shown that the fatigue strength of asphalt concrete, primarily associated with the complex quality of the bitumen binder, is the factor most affecting the projected period before the need for subsequent repair of asphalt concrete pavement.
As Mikhail Slavutsky noted, the standard methods used in the course of the research, based on the testing of asphalt concrete, are an order of magnitude more labor-intensive and longer than the methods based on the testing of bitumen binders in order to directly determine their fatigue characteristics without the manufacture of asphalt concrete samples. Then the expert revealed the essence of this technique, as well as the approach developed in ROSDORNIA to the comparative prediction of the expected timing of the actual need for repairs of asphalt concrete layers based on the results of tests of bitumen binders in the design of asphalt concrete.