The extensive asphalt research programme ASTO was carried out in Finland in 1987-1992. The ASTO programme consisted of 78 projects in all. The main products of the ASTO programme are the mix design system, the overall planning system, standards, norms and contracting system. With regard to the traffic and climate conditions in the Nordic countries, the most important issues have been the wear studies. The deformation of the surface layer has almost the same significance as wear resistance. Therefore new research methods, e.g. the wheel-tracking system or the repeated loading creep system, were developed for these purposes. Cold cracking itself is a very important issue in the Nordic countries. The range of countries. The range of temperature covering from -50 C up to + 50 C makes the situation very complicated. The best way to estimate the frequency of cracks is to perform a binder penetration test at + 5 C or a Fraass breaking test. The best systems for measuring the water-sensitivity of asphaltic mixtures were indirect tensile tests and water-mixing systems depending on the mixture type. The best way to measure the adhesion property of an aggregate was to use the water adsorption method. The compactibility of the asphaltic layer can be estimated in advance by the gyratory compactor. The mix design system is based on volumetric design principles. The reference level of the density is in maximum cases 406 gyratory cycles. The optimum binder content is defined using the VFB- value of 85%. The overall pavement design system consists of 4 different phases. The first is the initial mixture selection and the prediction of the life-time of different mixtures. In addition to this, the annual costs of the solutions are calculated in this phase. Second, the proper mix design is determined. Third, the functional properties of the mixtures are measured in the laboratory. Fourth, with the help of the levelling and structural measuring systems, the nature and the volume of the real construction can be estimated. (A)
Samenvatting