Search results for "Asphalt"
showing 10 items of 151 documents
An investigation of the mechanical properties of rubber modified asphalt mixtures using a modified dry process
2017
Incorporating recycling tyres into asphalt mixtures contributes to solving a serious environmental problem as well as the potential of improving the mechanical performance of asphalt mixtures. The recycled tyre rubber is added by two technologies known as the dry process (when rubber particles are treated as an aggregate modifier) and the wet process (when rubber particles are treated as a binder modifier). Although, the dry process is easier and requires minimal or no modification in the asphalt plant, the inconsistency in field performance makes the dry process not widely used. The main reason for this is believed to be the lack of interaction between the rubber particles and binder. In o…
Towards a new mix design method for asphalt mixtures containing rap
2016
Recycling is one of the most important aspects to conceive the new construction or rehabilitation of sustainable road infrastructures. Even if Reclaimed Asphalt Pavement (RAP) is commonly used in the practice, its presence may lead to some critical aspects due to the physical and chemical phenomena occurring during the new mix process. For instance, the formation of RAP clusters during a new mix may inhibit the uniform distribution of the virgin binder as well as cause changes in the design grading curve of the mixture. Indeed, laboratory results demonstrate that small-size RAP particles stick together forming clusters. The amount of clusters depends on different parameters observed: The pe…
An ANN model to correlate roughness and structural performance in asphalt pavements
2017
Abstract In this paper, using a large database from the Long Term Pavement Performance program, the authors developed an Artificial Neural Network (ANN) to estimate the structural performance of asphalt pavements from roughness data. Considering advantages of modern high-performance survey devices in the acquisition of road pavement functional parameters, it would be of practical significance if the structural state of a pavement could be estimated from its functional conditions. To differentiate various road section conditions, several significant input parameters, related to traffic, weather, and structural aspects, have been included in the analysis. The results are very interesting and …
Life Cycle Assessment of Asphalt Mixtures with WMR
2023
This study aimed at providing pavement specialists with international average values of greenhouse gas emissions (GHG) and energy consumption related to the manufacturing of asphalt mixtures (cradle-to-gate), with and without waste and secondary materials for roads (WMRs). In order to achieve this goal, TG leaders first referred to current standards to define a methodology for obtaining benchmark values according to ISO 21678:2020. Then, a data collection tool was designed and provided to a group of international partners to build a life cycle inventory for asphalt mixtures including data from materials up to plant manufacturing (A1–A3). Partners were asked to provide information for any ty…
Microstructural Study of Asphalt Mixture Containing Reclaimed Material
2012
In this paper mixing of reclaimed material with virgin asphalt material has been studied non-destructively. Specimens prepared with virgin asphalt mix and with asphalt mix containing reclaimed material were scanned in X-ray Computed tomography (CT). The obtained Images were analysed for particles and pores (air voids) distribution. All the specimens were also tested in compression test and X-ray scanned while testing. It was found that distribution of reclaimed is not uniform through the samples. There is no considerable effect of increasing the mixing time on particles' distribution. Similar trend of increase in air voids (cracks) with the increase in load was found for both virgin mix and…
Evaluation of dry asphalt rubber concrete in railway sub-ballast using the four point bending test
2016
The study of bituminous mixes can be related to tyre rubber material recycling. Encouraging scrap tyre disposal and cutting down on pit employment are the environmental aims. In the field of railways, technological processes involved in the use of crumb rubber are the wet-dry processes. In the mechanical characterisation of the asphalt concrete in terms of both the fatigue resista recycled waste tires nce and the stiffness modulus it is necessary to use a design method for the sub-ballast railway material, even more so if the asphalt concrete investigated is an innovative material such as a dry asphalt rubber concrete (DARC) (i.e. a bituminous mixture with crumb rubber formed by a dry proce…
Cold recycling of reclaimed asphalt pavements
2018
Pavement engineers have in front of them multiple challenges linked to addressing issues related to social development and society’s expanding needs. One of the most substantial of these issues is perhaps how to effectively rehabilitate and/ or maintain the existing road network while preserving and sustaining limited natural resources. The re-usage of existing pavement materials to reconstruct/ rehabilitate our future pavements is the solution that is now more and more selected by the different road administrations around the world. However, upon closer inspection, one can find many areas and details, not negligible issues, that are simply extensions of HMA technology (i.e. mix design proc…
Bitumen stabilized ballast: a potential solution for railway track-bed
2016
Railway ballast degradation under dynamic loads progressively leads to loss of mechanical performance and geometry of the track, so that maintenance interventions are frequently needed. In order to system- atically avoid this issue, recently solutions have been proposed to reinforce track-bed by using polyur- ethane and/or resins as well as asphalt layers among others. Nonetheless, their main limitations are related to the high initial cost and low productivity. To cope with these limitations, in this study, bitumen stabilized ballast (BSB) is proposed as a new solu- tion for ballast stabilization. This method aims at improving durability and reducing settlement by mod- ifying both stiffnes…
A Dynamic Model of Ballasted Rail Track with Bituminous Sub-Ballast Layer
2012
AbstractThe bituminous sub-ballast layer within the ballasted rail track allows some mechanical and environmental advantages. An analytical model of a ballasted rail track with sub-ballast layer has been proposed by considering the rail as viscous-elastic continuous beam discretely supported, at four levels of elasticity.The model was used to compare the mechanical performance of both ballasted track with and without bituminous sub-ballast layer. The results confirmed that the bituminous sub-ballast layer reduces the dynamic forces on the ground and achieves the technical objectives as reduction of ground borne vibrations and increase of the design life of the rail track.
Optimización de las propiedades de emulsión de betún para la estabilización de balasto
2017
Ballasted track, while providing economical and practical advantages, is associated with high costs and material consumption due to frequent maintenance. More sustainable alternatives to conventional ballasted trackbeds should therefore aim at extending its durability, particularly considering ongoing increases in traffic speed and loads. In this regard, the authors have investigated a solution consisting of bitumen stabilised ballast (BSB), designed to be used for new trackbeds as well as in reinforcing existing ones. This study presents the idea behind the technology and then focuses on a specific part of its development: the optimisation of bitumen emulsion properties and dosage in relat…