Review of approaches to determining the viscosity-penetration dependence of bituminous binders

Abstract

Abstract. Problem. The constant growth of load tension and traffic intensity on highways requires an increase in the quality and durability of asphalt concrete coatings. At present, conventional indicators for evaluating the quality of bituminous binders, such as penetration, softening temperature and brittleness, are still used in the vast majority of countries around the world. It is impossible to determine with the help of these indicators the characteristics necessary for the design of road clothing. Taking this into account, at the beginning of the last century, some researchers took steps to establish the relationship between standardized quality indicators (penetration, softening temperature, brittleness temperature according to Fraas) with fundamental ones, in particular, toughness. Goal. The purpose of the work is to consider, based on literature data, approaches to determining the viscosity-penetration dependences of bituminous binders, which have been developed for almost a century. Methodology. In order to achieve the set goal, a search was made for literary sources devoted to the issues of viscosity calculation, a critical review of them was performed, and the criteria for their application were established. Results. In 1933, Saal R.N.J. and Koens J. were the first to propose a formula that made it possible to calculate viscosity based on the value of a standard indicator - penetration. This gave impetus to an almost age-old study in which scientists from different countries of the world participated. The purpose of this study was to develop a numerical method for determining viscosity based on the value of penetration. Due to the fact that the quality of bitumen significantly depends on the raw materials from which they are made, manufacturing technology, group composition, structural and rheological type, for almost 90 years it was not possible to develop a dependence that would link the fundamental indicator with high accuracy (viscosity ) with standardized conditional (penetration). Despite this, the formulas proposed by various researchers formed the basis of two widespread road bitumen classification systems and the nomogram for determining bitumen hardness, which was used by designers of various countries of the world for 40 years. The analysis of these literary sources shows the persistent interest of researchers and manufacturers in the possibility of determining the viscosity values of bituminous binders by the calculation method, based on experimentally determined values of penetration. Practical value. It has been established that currently the task of calculating the viscosity based on the penetration value is becoming particularly relevant due to the fact that in modern conditions unmodified bitumens are being replaced by bitumens modified with various additives, for which the previously established dependencies are not valid.