| 1. |
- Bueno, Moises, et al.
(author)
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Modification of asphalt mixtures for cold regions using microencapsulated phase change materials
- 2019
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 9:1
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Journal article (peer-reviewed)abstract
- Phase change materials (PCMs) may be used to regulate the temperature of road surfaces to avoid low-temperature damages when asphalt materials become brittle and prone to cracking. With this in mind, different asphalt mixtures were modified with microencapsulated phase change materials (i.e. tetradecane) to assess their thermal benefits during the phase change process. Likewise, the effect on the mechanical performance of PCMs as a replacement of mineral filler was assessed. Special attention was paid to dry and wet modification processes for incorporating the PCMs into the mixtures. The results showed that PCM modifications are indeed able to slow down cooling and affect temperatures below zero. Approximately, a maximum of 2.5 °C offset was achieved under the tested cooling conditions compared to the unmodified reference specimens. Regarding the mechanical response at 0 °C and 10 °C, the results indicated that the PCM modification significantly reduces the stiffness of the material in comparison with the values obtained for the reference mixture.
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| 2. |
- Garcia, Alvaro, et al.
(author)
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Single and multiple healing of porous and dense asphalt concrete
- 2015
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In: Journal of Intelligent Materials Systems and Structures. - 1045-389X .- 1530-8138. ; 26:4, s. 425-433
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Journal article (peer-reviewed)abstract
- When the temperature of asphalt concrete is above a certain threshold, bitumen may start flowing through any possible crack and healing it. Induction heating is a technique for increasing the temperature of asphalt mixture. It consists of adding electrically conductive and magnetically susceptible particles to the mixture. These particles can be heated thanks to the action of an induction heating apparatus. The objective of this article is to investigate the effect of different asphalt mixture porosities and different types of bitumen on the induction-healing rates of asphalt concrete. With this purpose, semi-circular test samples made of porous asphalt mixture, with bitumen pen 70/100, and dense asphalt mixture, with bitumen pen 40/50, both of them containing steel wool fibres, have been analysed through successive three-point bending and induction heating tests. It has been found that the minimum temperature above which healing of asphalt mixture starts depends on the capacity for flow of bitumen at the threshold temperature. Moreover, the maximum healing level reached by asphalt mixture after damage is related to the type of bitumen used. Finally, it has also been found that successive heating of asphalt mixture may damage the structure of the material, reducing its healing capacity.
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| 3. |
- Rodriguez-Fernandez, Israel, et al.
(author)
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Microstructure analysis and mechanical performance of crumb rubber modified asphalt concrete using the dry process
- 2020
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In: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 259
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Journal article (peer-reviewed)abstract
- Globally, the vast majority of waste tires are landfilled, with catastrophic ecological consequences and in particular, serious threats to human health (e.g. fire, pests and soil contamination). Because of the increasing environmental awareness, the use of crumb rubber modified asphalt has become an important recycling strategy for waste tires. The so-called crumb rubber (CR), which is the recycled rubber from tires, has become a common additive in hot mix asphalt mixture due to its improvement of the mechanical performances of asphalt mixtures. The purpose of this study is to investigate the effect of adding crumb rubber to asphalt mixtures using the dry process by relating mechanical performances with microstructural characterizations. It was possible to observe the influence of conditioning process (time during which the asphalt mixture is kept at a high temperature after mixing) on the mechanical performance of the mixtures that depend primarily on the properties of the crumb rubber used. Specifically, it is shown that the conditioning time has an influence on the Marshall test results as well as the viscosity measurements. By using the Environmental Scanning Electron Microscope (ESEM), the distribution of the crumb rubber within the mixture has been investigated. In particular, the distribution of the crumb rubber by changing the conditioning time is of interest. The results showed that crumb rubber is well dispersed in the asphalt mixture when the conditioning time is increased. The effect of crumb rubber on the microstructure using Atomic Force Microscopy-Infrared Spectroscopy (AFM-IR) indicated that the main chemical change takes place in the para domain and catana or the so-called bee structures diminish on the CR modified bitumen as a consequence of more conditioning time.
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| 4. |
- Rodriguez-Fernandez, Israel, et al.
(author)
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Recyclability of Asphalt Mixtures with Crumb Rubber Incorporated by Dry Process : A Laboratory Investigation
- 2020
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In: Materials. - : MDPI. - 1996-1944. ; 13:12
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Journal article (peer-reviewed)abstract
- Semi-Dense Asphalt (SDA) mixtures are nowadays recommended for the surface layer of low noise roads in urban areas due to their optimal functional characteristics. Moreover, the use of polymer-modified bitumen (PmB) in its design results in high mechanical performance. However, this type of highly modified bitumen implies significant economic and environmental disadvantages. The polymer modification increases the production cost, involves higher mixing temperatures, and makes the recycling process of the asphalt mixtures challenging. As a potential alternative to PmB in SDA mixtures, this experimental work analyses the dry process for the incorporation of crumb rubber (CR) from waste tires. Particularly, the main objective was to study the aging effect and the recyclability of asphalt mixtures prepared in the laboratory with two different types of CR. The volumetric properties and mechanical performance of the mixtures artificially aged and rejuvenated were evaluated. The results obtained show that mixtures with CR have adequate performance, being less susceptible to aging than a conventional polymer-modified mixture. Furthermore, the rheological response of asphalt binder samples recovered from the mixtures at different aging states was analyzed. It was observed that the effect of the rejuvenator depended on the CR type, but this fact did not negatively influence the performance of the recycled mixtures.
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