G Kollaros

Bio: G Kollaros is an academic researcher. The author has contributed to research in topics: Pavement engineering. The author has an hindex of 1, co-authored 1 publications receiving 1 citations.

Pavements can last longer

Abstract: Scientific studies and experimental investigations are lately oriented in the field of long service life of hot mix asphalt pavements, regarding the increase of the useful life of their layers, through a less time-consuming and less costly procedure of rehabilitation and maintenance. In such a direction appears the idea of long lasting pavements. According to this concept, the expected pavement life reaches 50 years, and requires a periodical removal/replacement of the surface layer. It is important that this is achieved through a procedure completely environmentally friendly as it permits the recycling of the material of the old pavement and its placement again in the new pavement. The Perpetual Pavement offers engineers the ability to design for specific modes of distress in the HMA materials. Resistance to bottom-up fatigue cracking is provided by the lowest asphalt layer having a higher binder content or by the total thickness of pavement reducing the tensile strains in this layer to an insignificant level. The intermediate layer provides rutting resistance through stone-on-stone contact and the durability is imparted by the proper selection of materials. The uppermost structural layer resists rutting, weathering, thermal cracking, and wear. An effort has been made to study and understand the technical behavior of a standard four-layered pavement, under specific loading conditions, as well as the effect of the variability of these conditions on pavementrs longevity. In the frame of such tests the PerRoad software has been used. Reduction of damage per million equivalent single axle loads and increase in expected service-life has been achieved with increase of moduli and thicknesses of different layers.

On the Fatigue Criterion for Calculating the Thickness of Asphalt Layers

Abstract: The Israeli Flex-Design program for calculating the thicknesses of flexible pavement layers makes use of the asphalt fatigue equation to determine the thickness of the upper asphaltic layers. In this procedure, the values of the calculated asphalt layers decrease considerably with the increase in the granular basecourse modulus values for the same traffic volume. It has been shown, however, that the determination of the modulus of the granular basecourse by the Flex-Design program is not compatible with recent findings, thus leading to possible erroneous thicknesses for the upper asphaltic layers. In order to minimize these errors, the Flex-Design program has been accompanied by a limiting criterion for determining the minimum thickness of the upper asphaltic layers. This limiting criterion, which is a function of the number of design ESALs, actually leads to another accompanying limiting criterion for determining the maximum modulus of the granular basecourse, which is again a function of the number of design ESALs. These findings lead to the conclusion that the use of a pre-defined pavement-design catalogue for determining the upper asphaltic layer thickness is the most preferable way of proceeding. This catalogue exists in nearly all European countries. The same conclusion applies to the design of perpetual pavements (zero-maintenance pavements), for which a limiting maximum tensile strain of 70(S under an equivalent axle load of 80 kN exists. To recall, this strain is developed at the bottom of the asphalt layers.