1,721,307 research outputs found
Recycled and rubberized SMA modified mixtures: A comparison between polymer modified bitumen and modified fibres
No full textIn the presented research a series of Stone Mastic Asphalt (SMA) mixtures with and without Reclaimed Asphalt Pavement (RAP) and rejuvenating agent modified with SBS Polymer modified Binder (PmB) or composite Modified Fibres (MF) were optimized and investigated. In addition, beyond the common wet and dry methods of using waste tire rubber for producing asphalt mixtures, the rubber was added to the fibres with and without containing a plastomer polymer as a modifier. A comprehensive experimental programme including mechanical and performance tests were considered for evaluating the properties of the mixtures modified with PmB or MF with and without rubber and RAP. According to the test results, the SMA mixtures modified with MF were comparable with those of modified with PmB in most of the cases, however, the superiority of PmB mixtures were apparent in some cases. In the case of RAP addition, while it increased the tensile properties of corresponding mixtures observed by ITS and ITSM tests, it intensified the low-temperature sensitivity and reduced the fatigue life of mixtures containing rubberized fibres. Finally, the performance tests, moisture susceptibility and bitumen/aggregate, showed no significant difference between the tested mixtures in terms of moisture susceptibility and effectiveness of rubberized-fibres in bitumen binder's adhesion properties
The effect of Cryogenic Crumb Rubber in cold recycled mixes for road pavements
No full textOver recent years, the necessity of reducing the environmental mpact of building new infrastructures has increasingly directed research toward developing innovative manufacturing methods and materials that can satisfy these objectives. Cold recycling, widely used in renovating road pavements in Italy, is also moving in this direction, lowering the manufacturing temperatures of bituminous mixes and reducing or ultimately eliminating the use of virgin raw materials. Currently, a wide range of materials are used and, consequently, the number of variables to be considered in the mix-design process of cold recycled mixes for road bases is considerable. Furthermore, new products are continuously being introduced or developed for recycling purposes. The objective of this research project was to test the effects, both mechanically and environmentally, of crumb rubber included in 100% Reclaimed Asphalt Pavement cold mixes for road bases, bound with bitumen emulsion and cement. The crumb rubber is produced cryogenically with granulometric selection, which together with the bitumen, the cement and the fine fractions of the mix forms a resilient mastic capable of imparting significant fatigue resistance properties to the conglomerate. © 2014 Elsevier Ltd. All rights reserved
Recycling asphalt pavement and tire rubber: A full laboratory and field scale study
No full textThe present research deals with the influence of fine Crumb Rubber (CR) incorporation on the mechanical and performance characteristics of dense graded asphalt mixtures including 30% Reclaimed Asphalt Pavements (RAP) by means of both laboratory-scale and in situ tests. In the laboratory phase, the mixtures were evaluated in terms of Indirect Tensile Strength (ITS), moisture sensitivity, Indirect Tensile Stiffness Modulus (ITSM) and Repeated Load Axial Test (RLAT). Experimental tests indicated that while the difference of RLAT results were insignificant, the ITS values and the ITSM modulus changed in an effective way. On the other hand, the in-situ investigations on texture by means of sand patch and British pendulum provided testimonies to the effectiveness of CR in recycled dense graded mixtures. Finally, the tire/pavement noise emission measurements of the trial sections by means of Close Proximity (CPX) showed no significant difference between the tested pavements with and without rubber
Context sensitive design and safety review of bike lanes
Full text linkIn these days of increasing congestion on our roads, bicycles provide a valuable
contribution to mobility in Europe. Their relatively small size and low cost enable them to
blend efficiently into in the traffic flow while needing less space compared to other vehicles.
However, cyclists form one of the most vulnerable groups of road users. So the design of
safe infrastructures for all travelers categories, included the cyclists, becomes a primary
requirement. To obtain these results, Road Safety Audits and Road Safety Reviews are very
useful tool. In this paper the authors, starting from results collected on a bike lane placed in
Rimini, a city of Emilia-Romagna characterized by high bicycle traffic flows especially in
summer when many people head for this place for their holidays, provide useful results for
designers, construction and maintenance contractors, in order to obtain safe bike lane
Mechanical Characterization of Thin Asphalt Overlay Mixtures with 100% Recycled Aggregates
Full text linkAsphalt pavements inevitably deteriorate over time, requiring frequent maintenance work to ensure the proper serviceability of the road network. Small interventions, such as resurfacing for pavement preservation, are preferable to reconstruction at the end of roads’ in-service lives as they limit environmental- and economic-related impacts. Thin asphalt overlay (TAO) mixture represents a suitable maintenance solution to restore the functional properties of road surfaces. Due to the increasing awareness of the depletion of non-renewable resources and the importance of promoting the circular economy, this study evaluated the possibility of using fully recycled TAO mixes by investigating their volumetric and mechanical properties. Two eco-friendly TAO mixes were designed using recycled aggregates from reclaimed asphalt pavements, a municipal solid waste incinerator, and steel slags in order to meet EN 13108-2 requirements. The TAO mixes differed in regard to the type of bituminous binder (neat/SBS-modified bitumens) and fibres (natural/synthetic) employed. The preliminary results demonstrated that the presence of recycled aggregates did not negatively affect the workability and the mechanical performances of the two sustainable mixtures in terms of stiffness, tensile resistance, rutting and moisture susceptibility. Of these, the TAO mix with neat bitumen and synthetic fibres showed enhanced mechanical performance highlighting the structural effects of the used fibres
Road users’ behaviour in the "30 km/h zones". The case study of Bologna
Full text linkExcessive vehicle speeds in urban areas have resulted to be a major cause of road accidents involving pedestrians, cyclists, and motorcyclists, identified as "vulnerable road users" (VRU). A possible useful strategy to overcome this problem, both reducing speed and safeguarding vulnerable road users (VRU), is the introduction of "30 km/h zones". As traffic calming measures, they allow a maximum speed for drivers of 30km/h. The purpose of this study is to monitor the behaviour of drivers in the “30 km/h zones” of the centre of Bologna. With the close collaboration of Bologna Municipality, the study has provided for the monitoring of speed and type of transport in specific points within a selected circuit. Data collected showed that, although in most of the selected zones, speeds are below 30 km/h, in the areas where traffic is heavier, drivers exceed the permitted limit
Performance evaluation of recycled rubber waterproofing bituminous membranes for concrete bridge decks and other surfaces
No full textIn this paper a green waterproofing membrane for the protection of concrete decks is proposed. It is composed of a recycled rubber mat, sandwiched between two layers of SBS-modified bitumen. The rubber mat, itself, provides advantages in terms of environmental impact, because it is composed by a high density elastic mat made with granular rubber coming from the recycling of End of Life Tires, stuck with isocyanate and pressed. The polymer modified bitumen improves the interfaces adhesion and bonding, providing to the system a good water resistance. The rubber mat, different from the most common waterproofing membranes, is not supplied in rolls but can be applied in layers directly in work, according to the area to be covered. Laboratory characterization and a comparison to manufacturer's limiting values and tolerances of other available membranes confirm the overall performance and the use conformity of the proposed system
Experimental application of waste glass powder filler in recycled dense-graded asphalt mixtures
Full text linkThis paper presents laboratory study results, including both bituminous mastics and mixtures tests, to assess the use of glass powder (GP) as possible surrogate to limestone filler in recycled dense-graded asphalt mixtures. To achieve a comprehensive approach, the analysis has been divided into three parts including filler, mastics and mixture characterisation. The GP has been completely studied with chemical and physical tests to compare the fundamental characteristics to the commonly used limestone filler. In the second part, rheological tests using the Dynamic Shear Rheometer has been implemented to evaluate fillers interaction with not modified and modified bitumen. Finally, the mechanical properties of the asphalt mixtures containing GP filler were investigated in terms of indirect tensile strength, indirect tensile stiffness modulus and creep characteristics. According to the obtained results, GP filler provided comparable values to limestone filler within both mastic and mixture study. It is noteworthy that from the permanent deformation analysis, both MSCR and RLAT tests confirmed the improvement of rutting resistance with using GP filler
A complete laboratory assessment of crumb rubber porous asphalt
No full textBesides the many advantages of porous asphalt (PA), the permanent deformation resistance, fatigue strength, stripping and moisture susceptibility are not as good as for dense graded mixtures. In this research, the effectiveness of adding crumb rubber (CR) by dry method to PA mixtures was assessed. Rubberized porous asphalt (RPA) mixtures manufactured incorporating CR into SBS modified asphalt concrete were produced and compared with a control mixture by means of Indirect Tensile Strength (ITS), Indirect Tensile Stiffness Modulus (ITSM), moisture susceptibility, permeability, Cantabro, rolling bottle, draindown and creep tests. Results proved that although the application of CR reduces the vertical permeability and permanent deformation resistance, it improves the bitumen/aggregate affinity and it controls the draindown rate without adding fibres. On the other hand, the use of CR decreased the ITSM value at low temperature, which represents a lower susceptibility to thermal cracking. Other complementary test results in this research support the effectiveness of RPA mixtures
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