1,721,025 research outputs found
Editorial: RMPD Special Thematic Issue on Environmental Innovations for Asphalt Pavements
No full textParticle clustering phenomena in hot asphalt mixtures with high content of reclaimed asphalt pavements
No full textOne challenge in efficient recycling of asphalt concrete is the adherence of the reclaimed asphalt pavement (RAP) particles or clustering that inhibits fulfilling the aggregate gradation requirements. In order to investigate this phenomenon two types of mixtures containing virgin aggregates, bitumen and 50% and 90% RAP were investigated at different mixing temperatures. The formation of clusters in the mixture was verified using rheological properties (DSR) and imaging (ESEM, EDX). The virgin binder in the mixture was detected using imaging techniques by means of a titanium dioxide tracer and it was shown how the virgin binder surrounded the clusters of RAP depending on mixing temperature. (C) 2015 Elsevier Ltd. All rights reserved.LAVO
Induction healing of fatigue damage in asphalt test samples
No full textTo promote asphalt self-healing, asphalt mixture can be heated via induction heating. This technique consists in adding electrically conductive and magnetically susceptible particles (e.g. steel) into asphalt mixture; then, with the help of an induction heating machine asphalt mixture can be heated. When the temperature of asphalt mixture is above a certain threshold (between 30 °C and 70 °C, depending on the type of bitumen), microcracks start self-healing. Induction healing has been previously demonstrated for repairing asphalt mixture test specimens broken in two pieces, but this technique has never been used for repairing microcracks caused by fatigue damage. In this article, the optimum moment and temperature needed to repair asphalt mixture under fatigue damage have been experimentally determined. With this purpose, Marshall test specimens have been damaged through indirect tensile fatigue tests and healed via induction heating. Finally, damage and healing have been quantified through computed tomography scan tests
Use of reclaimed asphalt in porous asphalt mixtures: Laboratory and field evaluations
No full textMaintenance and reconstruction of road pavements involve the production of huge amount of discarded material, such as reclaimed asphalt (RA), every year. As a consequence, issues related to RA stockpiles and disposals are dramatically increasing. At the same time, the growing importance of environmental and economic matters has led researchers and engineers to promote reusing milled materials rather than using valuable and nonrenewable natural resources (bitumen and aggregates). Road pavement maintenance and construction usually involve the use of porous asphalt (PA) mixtures, in particular in the case of motorways and highways. In fact, PA mixtures are widely employed as pavement surface layer thanks to their ability in reducing traffic noise and enhancing safety in wet conditions. In this sense, the reuse of RA into PA should be strongly encouraged. Unfortunately, technical specifications adopted in many countries do not allow any recycled materials in porous asphalt surface layers yet. Thus, reliable techniques allowing the use of RA in new PA mixtures are needed. In this research study, the use of coarse RA from old PA as aggregate in new PA mixtures was evaluated. Because a previous laboratory study demonstrated that the use of 15% of RA aggregates in PA mixtures seems possible (or even recommendable) as long as an accurate mix design with adequate binder contents is performed, new laboratory and field evaluations on recycled PA mixtures with15% of RA aggregates were carried out. On one hand, cyclic coaxial shear tests (CASTs) were performed under both dry and water-submerged conditions in order to evaluate the simultaneous effect of traffic and water exposure. On the other hand, a comprehensive laboratory experimental program for assessing acceptability, durability, fracture resistance, and water sensitivity was carried out on materials taken from the field during the construction of a full-scale trial section. Moreover, drainage properties of surface layers were measured along such a trial section. Overall test results demonstrated that including 15% of selected coarse recycled aggregates into porous asphalt mixtures does not compromise performances and durability of both asphalt-plant and laboratory produced mixtures. It was demonstrated that recycled mixture with 5.25% of total binder content and prepared by accurate mix design can perform as well as (or even better than) standard PA mixture in terms of workability, acceptability, abrasion resistance, repeated loading resistance, fracture propagation resistance, moisture sensitivity, and water drainability
Fatigue performance of Stone Mastic Asphalt designed with the Bailey’s method
No full textThis paper presents the results of a laboratory analysis and a theoretical study on the fatigue performance of Stone Mastic Asphalt (SMA) mixtures, evaluated by the four-point bending test. The trial was performed on SMA mixes made with Electric Arc Furnace (EAF) steel slags and Coal Bottom Ash, integrated in the aggregate skeleton in partial substitution of natural limestone and filler, respectively. The Bailey’s method as well as a conventional trial and error approach, were used in order to design the grading curves of the mixes. The bitumen content evaluation was based on the optimization of the volumetric properties and the moisture resistance of the SMA mixtures, using the gyratory compactor and the indirect tensile test. The purpose was that to compare the fatigue resistance of the mixtures designed by means of Bailey’s and the trial and error procedures, considering both the empirical approach, related to a 50 % reduction in the initial stiffness modulus and the dissipated energy analysis, which allows a more rational evaluation of the fatigue performance. Bailey’s SMA mixtures presented better fatigue behaviour than the reference mixes designed with the trial and error procedure. Moreover, with respect to the control SMA mixes prepared with natural aggregates, the mixes made with EAF slags and Coal ash showed improved fatigue properties. © RILEM 201
Advanced interface testing of grids in asphalt pavements
No full textNowadays, road pavements are subjected to steadily increasing traffic volumes generating accelerated functional and structural distresses that require frequent and expensive maintenance. On the basis of such needs, in recent years, practical applications and theoretical studies have proved that the service life of flexible pavements can be extended by installing geosynthetic reinforcements. In particular, grids can be placed at the interface of bituminous layers for both new constructions and rehabilitation of existing pavements, in order to improve repeated loading and rutting resistance and to prevent or delay reflective cracking. However, the presence of an interlayer reinforcement may also hinder the full transmission of horizontal shear stress between asphalt layers (debonding effect), penalizing the overall efficiency of the pavement system. For the above-mentioned reasons, both laboratory and in situ investigation are needed in order to better understand the real role played by the grid reinforcement. The achievement of such objective is the main goal of the RILEM TC 237-SIB/TG4 that carried out an interlaboratory experiment focused on the âAdvanced Interface Testing of Geogrids in Asphalt Pavementsâ. In this context, the participating laboratories were involved with a twofold objective: to compare the predictive effectiveness of different experimental approaches and to analyze the behavior of different grid types. For this purpose, two experimental reinforced pavement sections were realized with the same materials and construction techniques. The first pavement section was used to prepare samples for the interlaboratory experiment, the second one was specifically designed and instrumented to analyze the field performance of the grids under heavy traffic conditions. The objective is the characterization of the mechanical behavior of grid reinforced interfaces in asphalt concrete pavements using different test methodologies and the analysis of the relationship between laboratory test results and actual field performance. To this purpose, the laboratory research activities were based on the analysis and comparison of the results obtained following specific testing protocols proposed by the participating laboratories that combine performance-based tests (e.g. interlayer shear tests, static and dynamic bending tests, tensile-bending tests), in order to investigate the overall behavior of double-layered asphalt systems. The role of the instrumented pavement section was complementary and oriented towards an improvement in the existing design and testing approaches. Such goal was attained by analyzing the actual stress-strain response of grid-reinforced systems under vehicular loads, also monitoring the natural and induced field cracking evolution. Despite the variety of the testing equipment and protocols adopted by the participating laboratories, all test results were consistent. Moreover, such experimental results contributed, together with the data analysis collected on the instrumented pavement section, to the correct understanding of the grids performance that were characterized by specific peculiarities making them appropriate for different applications
A multi-scale fundamental investigation of moisture induced deterioration of porous asphalt concrete
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Inter-laboratory shear evaluation of reinforced bituminous interfaces
No full textOver the last decades, the use of grids between asphalt layers has been gaining interest. Several test methods have been proposed in order to simulate the complex mechanical behavior of reinforced pavements and to assist practitioners in the selection of the appropriate reinforcement product. For this purpose, the Task Group 4 (Pavement Multilayer System Testing) of the RILEM technical committee TC 237-SIB (Testing and Characterization of Sustainable Innovative Bituminous Materials and Systems) organized an inter-laboratory experiment, constructing one trial test section to obtain double-layered asphalt pavement samples for the participating laboratories. The experiment placed two grid types (a glass fiber reinforced polymer grid and a carbon fiber/glass fiber pre-bituminised grid) between two asphalt layers, thereby creating two reinforced double-layered systems. As a control, an unreinforced interface was also realized. This paper presents the overall results of interlayer shear tests carried out by five participating laboratories using five different shear testing methodologies. The objective is to show the effect of two grid types on the shear behaviour of reinforced double-layered systems and to compare the findings which emerged from using different test devices and methods
under different testing conditions (e.g. sample geometry, temperature, loading time, normal stress). Consistent and reliable results have been obtained through the various methodologies adopted. It has been observed that grid-reinforced samples provide lower interlayer shear strength compared with unreinforced samples. Glass-fiber grid system, which is of greater thickness and greater torsional stiffness, displayed less shear strength than carbon fiber/glass fiber-reinforced grid systems
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