1,721,137 research outputs found
Analisi Sperimentale e Modelli Teorici per lo Studio del Comportamento a Taglio delle Interfacce nei Sistemi Bituminosi Multistrato
No full textInfluenza della Temperatura sulla Resistenza a Taglio delle Interfacce di Pavimentazioni Flessibili Multistrato
No full textTensile and Shear Tests of Interfaces in Asphalt Mixes: a New Prospective on Their Failure Criteria
No full textStudio della Ripetibilità della Prova Prestazionale ASTRA sui Trattamenti Superficiali di Irruvidimento
No full text
Determination of equivalent axle load factors with the use of strain energy of distortion
No full textThe paper proposes a new method for calculation of equivalent axle load factors based on the analysis of strain energy of distortion induced in road pavements by traffic loads. The main advantage of the method is the more accurate calculation of the effects of multiple axles and super single versus dual tyres. The methodconsiders the location of critical points, at which strain energy of distortion reaches extreme values. When single axles are considered, the function of equivalent axle load factor takes on the form of the well-known power equation with the exponent ranging from 2.7 to 5.3. It was proved that the damaging effect of triple axles on asphalt pavement is several times higher than the damaging effect of three single axles carrying the same load, but at a greater distance to each other. Due to this fact, traffic load may be significantly underestimated in many pavement design methods
VECD analysis to investigate the performance of long-term aged bio-asphalt mixtures compared to conventional asphalt mixtures
No full textThe road industry is seeking solutions to reduce its dependency on petroleum-based products and its carbon footprint. This is leading to increasing interest in the so-called bio-binders, i.e. binders in which bitumen is partially replaced with bio-oils from renewable sources. Fatigue cracking is a major distress for flexible pavements and therefore the fatigue behaviour of innovative road materials (such as bio-asphalt mixtures) must be characterised in a reliable way. Within this framework, this study aims at comparing the fatigue behaviour of a bio-asphalt mixture and the corresponding conventional asphalt mixture. The two mixtures were laboratory-mixed and laboratory-compacted, and the only difference between them was the binder (a bio-binder containing 10% of wood-based bio-oil vs. a conventional bitumen having physical and rheological properties similar to the bio-binder). The mixtures were short- and long-term aged in the laboratory and subjected to complex modulus tests and cyclic fatigue tests. The results, analysed according to the viscoelastic continuum damage (VECD) theory, showed that, after short-term aging, the bio-asphalt mixture may be slightly stiffer and thus more prone to cracking than the control mixture due to a possible over-aging caused by the effects of high temperatures. However, the long-term aging susceptibility of the bio-asphalt mix was found to be less severe as compared to the control mix, leading to fatigue performance benefits in the long term and corroborating the results of previous investigations at the binder level. Overall, these findings further encourage the use of bio-binders as an alternative to traditional asphalt binders
A review of top-down cracking in asphalt pavements: Causes, models, experimental tools and future challenges
Full text linkIn the last decades, a new type of distress has been observed more and more frequently on asphalt pavements. This distress, ascribable to fatigue failure, has been named top-down cracking (TDC) because it consists in longitudinal cracks that initiate on the pavement surface and then propagate downwards. A series of surveys recently carried out on Italian motorways highlighted that TDC can affect up to 20%–30% of the slow traffic lane. Therefore, in order to achieve a better understanding of such distress, this paper reviews causes, models and experimental tools and highlights future challenges for TDC. The literature review indicates that TDC can evolve on the pavement surface in three stages (i.e., single crack, sister cracks, alligator cracking) and, below a certain depth, the cracks can form angles of 20°–40° with respect to the vertical plane. Even though multiple factors contribute to TDC development, thick pavements are more likely to fail due to TDC induced by tire-pavement contact stresses, especially in the presence of open-graded friction courses (OGFCs). Moreover, in literature there are several TDC models based on mechanics (e.g., fracture mechanics or continuum damage mechanics) which allow a rigorous study of crack initiation and propagation. Future challenges include the identification of a reliable and feasible test method, among those proposed in literature, to study the TDC performance of asphalt mixtures and the implementation of TDC in pavement management systems (PMSs) through the definition of criteria for TDC recognition in the field as well as for the rehabilitation depth evaluation. Finally, more research is needed for open-graded asphalt mixtures, which present critical drawbacks in terms of TDC
Temperature Effects on the Shear Behaviour of Tack Coat Emulsions Used in Flexible Pavements
No full textIn this paper, the authors present the experimental results obtained in the laboratory by using the ASTRA interface shear test for the performance-related characterisation of tack coat emulsions. The test focuses on the failure properties of bituminous multi-layered systems and yields results which may be modelled by means of a straightforward theoretical approach based on the identification of various strength components due to cohesion, pure friction and dilatancy. It was found that the latest version of the testing apparatus may be conveniently used to evaluate temperature-related effects. This was done in a research project in which test conditions were obtained by combining test temperatures and normal stress levels comprised within wide variation range
- …
