1,720,996 research outputs found
Interlayer bonding properties of warm recycled asphalt pavements
No full textThe need for sustainable road infrastructures has led to great interest in Warm Mix Asphalt (WMA) technologies, which allow the production, lay-down and compaction of asphalt mixtures at reduced temperatures, about 40 degrees C lower than traditional Hot Mix Asphalt (HMA). The use of WMA ensures lower emissions and is also beneficial in the recycling of Reclaimed Asphalt (RA) deriving from the milling of end-of-life pavements. One of the main concerns regarding WMA is the possible poor adhesion between the pavement layers that could be caused by the reduced working temperatures during the paving operations. However, almost no data are currently available in literature on this aspect, which thus could represent a deterrent to the wide application of WMA by road agencies. In this regard, this paper focuses on the investigation of the interlayer bonding properties of warm recycled asphalt pavements constructed along various Italian motorways and national roads using different WMA chemical additives. The Interlayer Shear Strength (ISS) was measured at different pavement interfaces (wearing-binder, binder-base) and time intervals by testing extracted cores with ASTRA and Leutner equipment. The results show that the interlayer bonding properties of WMA pavements are comparable to HMA pavements and are not affected by the WMA additive type. Moreover, ISS depends on the properties of the tack coat applied between the layers and increases over time due to aging effects, especially when the interface is below an open-graded friction course (OGFC). These findings further encourage the use of WMA as environmentally sustainable technologies for the construction and maintenance of asphalt pavements
Interlayer bonding design of porous asphalt course interface
No full textInterlayer bonding affects performance of asphalt concrete pavements. In order to guarantee good bonding, tack coats are frequently applied at various interfaces. Interlayer bonding design consists in the determination of the optimum tack coat rate and the ASTRA (Ancona Shear Testing Research and Analysis) test method can be used for this purpose. In this study, the tack coat design of the interface between an existing porous asphalt and a newly laid open graded course was developed. In order to check whether the two porous layers are independent or behave as a Twinlay, the drainability of the resulting double-layered system was also investigated. The ASTRA tests showed that acceptable interlayer bonding results can be obtained for each emulsion rate studied but higher tack coat rates mitigate the scatter of the results. In terms of drainability, the porosity of the existing layer does not increase the drainage characteristics of the double-layered system, for each interface treatment considere
Performance Optimization of Warm Recycled Mixtures
No full textWarm Mix Asphalt (WMA) technologies are becoming popular due to their ability to reduce mixing and compaction temperatures compared to the conventional hot mix asphalts (HMAs), with remarkable advantages of environment and costs. Moreover, WMA is considered as one of the most promising technology for increasing the re-use of Reclaimed Asphalt (RA) within the mixture although its effectiveness in recycling issues require more dedicated research activities. This paper describes a laboratory investigation aimed at optimizing a dense graded asphalt mixture for wearing course, produced with WMA technology and including up to 30% of RA. WMA mixtures were prepared by using two contents of a plain bitumen, two contents of RA and one chemical additive. A recycled HMA containing lower RA content, according to technical specifications currently applied in Italy, was selected as reference mixture. Strength and stiffness properties, water sensitivity, rutting and cracking resistance were investigated on shear gyratory compacted specimens. The result analysis on stiffness, rutting and fracture properties indicated the possibility to produce suitable WMA mixtures with higher RA contents without penalizing their performance compared to the reference one
Comparing the field and laboratory curing behaviour of cold recycled asphalt mixtures for binder courses
Full text linkThe cold recycling of reclaimed asphalt (RA) for the rehabilitation of end-of-life pavements is becoming very common. Cold recycled asphalt mixtures (CRAMs) are characterised by a curing time, required to reach the material design mechanical performance. Since the laboratory simulation of the long-term field curing is not yet a standardised procedure, a CRAM was laid as binder course in a full-scale trial section that was monitored for more than two years. The comparison between field curing and oven-curing in laboratory at 40◦C was performed by carrying out indirect tensile stiffness modulus (ITSM), indirect tensile strength (ITS) and complex modulus tests, as well as measurements of the air voids content. The evolution of the ITSM as a function of the curing time (field/oven-curing) was obtained for both gyratory specimens and cores taken from the trial section at different time periods. Results showed that the material stiffness development can be accelerated with a small effect on its long-term value if oven-curing is applied a few days/weeks after compaction. A linear relationship was found between the ITS measured on the cores and their air voids content. Finally, the complex modulus tests confirmed that CRAMs provide an intermediate behaviour between asphalt concrete mixtures and cement-bound mixtures
Renewable materials in bituminous binders and mixtures: speculative pretext or reliable opportunity?
No full textBitumen is the most employed binder in road pavements and derives from petroleum, which is a non-renewable resource that is progressively depleting. Therefore, the current challenge for road industry is to use renewable materials (i.e. bio-materials not subjected to depletion) in partial replacement of bitumen, thus reducing carbon footprint and making the sector less dependent on petroleum-based products. Specifically, the trend is to utilize bio-materials that are obtained as by-products from industrial processes or as wastes from the everyday life, avoiding their disposal in landfills, in accordance with the principles of sustainability and circular economy. Thus, research in this field is very promising and attractive nowadays. However, in order to understand whether the application of renewable materials represents a reliable and viable solution or just a speculative pretext for research, a rigorous scientific approach must be adopted. For this purpose, the paper provides an overview of the use of renewable materials in bituminous binders and mixtures, focusing on the necessary requirements that they should meet, their effects on performance, and health, safety and environment aspects. Based on the analysis of available literature, a comprehensive experimental approach for evaluating bio-materials in bituminous applications is also proposed
Interpretazione del Ruolo delle Mani d’Attacco nelle Pavimentazioni Flessibili
No full textAtti dell'Istituto di Idraulica e Infrastrutture Viari
Asphalt Binder Modification with Plastomeric Compounds Containing Recycled Plastics and Graphene
No full textPolymer-modified bitumens are usually employed for enhancing the mixture performance against typical pavement distresses. This paper presents an experimental investigation of bitumens added with two plastomeric compounds, containing recycled plastics and graphene, typically used for asphalt concrete dry modification. The goal was to study the effects of the compounds on the rheological response of the binder phase, as well the adhesion properties, in comparison with a reference plain bitumen. The blends (combination of bitumen and compounds) were evaluated through dynamic viscosity tests, frequency sweep tests, and multiple stress creep recovery (MSCR) tests. Moreover, the bitumen bond strength (BBS) test was performed to investigate the behavior of the systems consisting of blends and aggregate substrates (virgin and pre-coated). The rheological tests indicated that both blends performed better than the plain bitumen, especially at high temperature, showing an enhanced rutting resistance. In terms of bond strength, comparable results were found between the blends and reference bitumen. Moreover, no performance differences were detected between the two types of blends
Effect of temperature and chemical additives on the short-term ageing of polymer modified bitumen for WMA
No full textNowadays warm mix asphalt (WMA) is recognized as a very competitive alternative to hot mix asphalt (HMA). This technology allows to obtain an excellent and environmentally-friendly material for road construction. This paper focuses on the effect of a reduced short-term ageing temperature on the binder behaviour and on the effect of WMA chemical additives on the performance of short-term aged binders. Three asphalt binders (one polymer modified bitumen combined with two WMA chemical additives) were aged through the rolling thin film oven test (RTFOT) at different temperatures (120, 130 and 163 degrees C). Conventional, rheological and chemical tests were used for characterising the binders. Lower ageing temperatures provided reduced oxidation, implying lower oxidative hardening but also reduced permanent deformation resistance. A general reduction of ageing effects is observed in the WMA binders, with both positive (moderate deceleration of the ageing process) and negative (more noticeable reductions in the permanent deformation resistance) outcomes. The microscopic analysis showed that the chemical additive likely alters the structural interactions of bitumen and polymer. A comparison between WMA binders short-term aged in laboratory and in field, indicates that the RTFOT performed at reduced temperature could properly simulate the field ageing when WMA production temperatures are considered
Experimental characterization of high-performance fiber-reinforced cold mix asphalt mixtures
No full textMaintenance of existing road pavements assumes increasing interest as the traffic growing produces a
faster deterioration of road infrastructures compromising safety and pavement serviceability. In order
to guarantee long-lasting pavement repairs, maintenance activities and products must be optimized in
terms of both achieved performance and curing times to reach a proper pavement serviceability. This
research project focuses on the experimental characterization of a high-performance cold mix asphalt
mixture reinforced with three types of fibers (cellulose, glass–cellulose, nylon–polyester–cellulose) dosed
at two different contents (0.15% and 0.30% by the aggregate weight). Such materials were investigated at
different curing times (1, 7, 14, 28 days) and conditions (dry and wet). Laboratory tests (Marshall, Indirect
Tensile, Abrasion and Compactability) usually employed for hot mix asphalts were considered, adjusting
the testing procedures taking into account the specific characteristics of cold mixes. Results showed that
the mix with 0.15% cellulose fibers provides similar (for curing times of 14 and 28 days) or even higher
performance (for curing times within 7 days) than the standard mixture (without fibers). Finally, the last
two mixtures were compared with two cold mix asphalt mixes available on the market. The cellulosefiber-
reinforced material and the standard one showed enhanced performance, allowing the conclusion
that they can be more successfully used in maintenance activities
- …
