1,721,122 research outputs found
Effects of different aging methods on chemical and rheological properties of bitumen
No full textBitumen 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.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Pavement Engineerin
A Study on Texture and Acoustic Properties of Cold Laid Microsurfacings
No full textAbstractSlurry microsurfacing is an economical maintenance intervention that provides effective skid resistance and surface evenness in a thin layer, thus improving the road safety. Researchers aimed to develop an innovative application of slurry seal, capable of gathering in a single material some technical solutions for various functional and environmental aspects. The purposes of this intervention are: restoring skid resistance, sealing surface cracking, reducing tire/pavement noise, adding crumb rubber from tires as a recycling material and reducing atmospheric emissions using the cold technique. A 3D laser scanner device has been used to evaluate the surface texture and analyze the roughness parameters
A challenge for a more sustainable urban mobility in Europe
No full textAs cities worldwide endeavor to make their transport portfolio more sustainable, cycling is increasingly relied on as an essential component. In Europe, especially in countries such as Netherlands or Denmark, this interest is not recent at all but, on the contrary, in other countries as Italy it is recent. The major consequence is that the infrastructural system must be gradually performed to the changing mobility and the integration of cycling paths must be outlined in urban mobility plans.
To obtain these results, is very important to know where and when cyclists ride in the city and to have a detailed feedback about cyclists' real needs. Cyclists, in fact, while relatively small in numbers in proportion to motorized vehicles, have a high level of vulnerability, creating a significant need to better understand the specific features of this users group.
For this reason, the city of Bologna promotes every year the European Cycling Challenge, a friendly city team competition among urban cyclists.
At the end of the European Cycling Challenge, all GPS data collected through the app provide a very detailed and big amount of information on the behaviors of cyclists in the city. These data are very important for city planners, because they can check the efficacy of the existing cycle-lane network and they can plan the future of the mobility in their city based on the real needs of citizens
Effects of hazardous spills by road accidents on pavement texture and its deterioration mechanism
Full text linkHazardous spills from road accidents affect road safety, reduce the skid resistance of pavement and have a long-term impact on pavement texture. This paper conducted experimental investigation and molecular dynamics simulations on common road accident hazardous spills (petrol, diesel, engine oil, and brake fluid). A low-cost close-range photogrammetry technique was used to measure changes in pavement texture. The texture wear process of the contaminated pavement was simulated by using the Hamburg Wheel Tracking Device. Material Studio was used to simulate the interaction between hazardous spills and the bituminous conglomerate. Results showed an average reduction of 47 % in terms of skid resistance after contamination, with an absolute maximum decrease of 71 % observed with engine oil spillage. While cleaning can partially restore skid resistance, effects of contamination vary by spill type. Petrol and diesel dissolve bitumen, weakening the pavement structure, whereas engine oil remains on the surface, posing prolonged safety risks. Brake fluid infiltrates aggregates, potentially affecting their mechanical properties. The correlation between texture parameters and skid resistance is weak on newly paved roads but become more pronounced as wear progresses. Simulations reveal that hazardous spills adhere readily to bitumen and aggregates, exacerbating contamination effects. These findings provide scientific insights for optimizing spill response strategies and improving road safety management
Assessing the evolution of Public Transportation demand over time based on real data through survival analysis in Bologna, Italy
No full textPublic Transportation (PT) is a universal service in most countries, and it is acknowledgedfor its social and environmental role in enhancing accessibility and promoting a sustain-able transport system. However, when disruptions alter the service, the level of service(LoS) can be massively affected. Consequently, the perceived quality can be influenced,and users can be encouraged (or forced) to modify their subsequent modal choice, inaccordance with the users’ socioeconomic profile. A survival analysis, namely a Cox proportional hazards model, was tested in Bologna, Italy, using real data provided by TPERS.p.A, specifically Automatic Vehicle Location (AVL) and Automatic Passenger Counter(APC). This analysis aimed to assess the variations in demand over time taking into ac-count variables related to the socioeconomic characteristics of the demand and severalservice attributes. The results contribute to the literature in several ways. Firstly, theyconfirm the predominant role of PT in the modal alternative spectrum of disadvantagedusers. Secondly, they provide insights into the perception of quality service among different user categories, including commuters and non-frequent users
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
Semi-automatic evaluation of the degree of bitumen coverage on bitumen-coated aggregates
No full textEN 12697-11 is the standard providing test methods for evaluating affinity between aggregate and bitumen and its influence on the susceptibility of the mixture to stripping. Among the methods, the rolling bottle test has a number of advantages in terms of rapidity, low costs, and suitability for routine testing. However, since affinity is assessed by visual registration of two independent operators, results may be altered by a large amount being inevitably subjective. The authors suggest a semi-automatic procedure to overcome potential limits and shortcomings of the method and obtain accurate results. Different mixtures were analyzed and compared, using common natural and recycled aggregates and a 70/100 pen bitumen. The procedure was successfully validated with a manual pixel inspection and confusion matrixes were created. The results showed that the procedure lead to a more reliable registration compared to the standard method and it is suitable, with different accuracies, for both light and dark aggregates
American and European Mix Design Approaches Combined: Use of NCHRP Performance Indicators to Analyze Comité Européen de Normalisation Test Results
No full textThis 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
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
Fixation distance and fixation duration to vertical road signs
No full textThe distance of first-fixation to vertical road signs was assessed in 22 participants while driving a route of 8.34 km. Fixations to road signs were recorded by a mobile eye-movement-tracking device synchronized to GPS and kinematic data. The route included 75 road signs. First-fixation distance and fixation duration distributions were positively skewed. Median distance of first-fixation was 51 m. Median fixation duration was 137 ms with a modal value of 66 ms. First-fixation distance was linearly related to speed and fixation duration. Road signs were gazed at a much closer distance than their visibility distance. In a second study a staircase procedure was used to test the presentation-time threshold that lead to a 75% accuracy in road sign identification. The threshold was 35 ms, showing that short fixations to a road signs could lead to a correct identification
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