This paper describes a project that is part of NL-LAB, a larger, long-term program at Delft University of Technology, Netherlands, which aims to establish the predictive capacity of the current European functional tests for Dutch asphalt concrete (AC) mixtures. In this NL-LAB program, the functional characteristics of resistance to rutting (EN 12697-25), fatigue (EN 12679-24), stiffness (EN 12697-26), and moisture sensitivity (EN 12697-12 and EN 12697-23) are determined for specimens that are (a) mixed and compacted in the lab, (b) mixed in the plant and compacted in the lab, and (c) mixed in the plant and compacted in the road. Eventually, these tests will provide insight into the effect of mixing and compaction on the functional characteristics. The project described in this paper focused on the indirect tensile strength (ITS) and the triaxial cyclic compression test for two AC mixes. The properties found for all three stages of preparation were analyzed with the use of formalistic expressions from the NCHRP Design Guide 1-37A, Level 2, for the estimation of performance indicators. This project aimed to see if these relations remained valid for the Comité Européen de Normalisation tests, especially for mixes with high recycled asphalt pavement content. In the Netherlands, 50% reclaimed asphalt pavement is standard. It was found that the NCHRP Design Guide 1-37A expressions fit the Comité Européen de Normalisation test data quite well for the reclaimed asphalt pavement that contained mixes, especially for the ITS. Currently, another two construction projects are being sampled, and the results will be used to validate and improve the relations.@en

In the Netherlands, the functional approach described in the 2008 European Asphalt Concrete standards was selected, specifying mixtures by their stiffness, fatigue resistance, permanent deformation, moisture sensitivity and limited composition data. The requirements for the functional specifications were based on the existing experience with a large number of mixes. Since the introduction of the standards, unexpected developments like improved performance in all functional tests with increasing RAP content, led to questions about the predictive quality of the laboratory determined functional characteristics for field performance and the potential causes of a mis-match between lab and practice. These questions led to a large, long term project in the Netherlands (NL-LAB) in which the functional characteristics are determined in the process of construction projects. They are determined on (I) material mixed and compacted in the lab, (II) mixed in the plant and compacted in the lab and (III) mixed in the plant and compacted in the road. These tests will eventually provide insight in the effect of mixing and compaction. The pavement sections are monitored in time, to allow the link with pavement performance. The sections will be sampled during their service life to see changes occur in their functional properties. For the road industry, that tries to guarantee pavement performance by accurate selection of materials, the possibility of design information based on both laboratory and in situ results would be beneficial. Two mixes for base layers with different mix compositions and amounts of RAP are analysed using formalistic expressions originating from Design Guide Level II for estimation of various performance indicators. This project uses expressions to analyse the differences between the mixes in the three cases described above. It addresses the possibility of utilizing these expressions during preliminary mix design to guide the selection of mix composition parameters towards a desired optimum.@en

Bitumen undergoes ageing, which leads to changes in its chemical and rheological properties, causing it to become harder and more brittle with time. This study aims to compare the effects of different laboratory ageing methods on the chemistry and rheology of three bitumen types: a Pen 40=60, a Pen 70=100, and a polymer-modified bitumen (PmB). Four ageing protocols were applied: ageing at room temperature, oven ageing, pressure ageing vessel (PAV), and rolling thin-film oven test (RTFOT) combined with PAVageing. The effects of temperature, pressure, and ageing time were studied using dynamic shear tests and infrared spectroscopy. The results highlight the relationship between chemistry and rheology of bitumen. Bitumen hardening, which was revealed by an increase in complex modulus and a decrease in phase angle, was reflected in the growth of specific chemical functional groups. Among all materials, soft bitumen showed the greater tendency to oxidize. Different behavior was observed for PmB, which presented the highest resistance against oxidation among the studied bitumens, even though the reaction with oxygen caused the deterioration of the added polymer modifiers.@en

Environmental protection is also pursued by promoting the saving of oil reserves and the proper management of waste through a circular economy. Following this objective, the present study encourages the use of recycled and by-product materials for the production of bituminous binders. The powdered rubber (R) from end-of-life tyres and the re-refined engine oil bottom (REOB), i.e. the by-product of refining mineral waste oils, were used to replace a certain amount of standard bitumen. The experimental program aims to characterize the interaction between R and REOB in order to use them as virgin bitumen extenders. The multiple variables of the production process that may affect the R-REOB blends and in turn the binders’ final properties were evaluated. The R-REOB mixes were prepared by varying the type of REOB, the R content and the mixing temperature. The rheological analysis was performed by means of dynamic shear rheometer (DSR) tests with the aim to define the variables that strongly influence the response of the R-REOB compound. As a result of this preliminary study, the second phase will focus on extended bitumens that will be prepared considering some of the studied extenders.@en