Ethanol based foamed asphalt as potential alternative for low emission asphalt technology (original) (raw)
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Study on Water Sensitivity of Foamed Asphalt Mixture Based on Chemical Thermodynamics
Because small amount of water is incorporated during the foaming process, water sensitivity of warm mix asphalt has become a research interest. The asphalt layer may fail prematurely in the presence of water especially when it is poorly designed and constructed. The cohesive bond of the mastic (asphalt binder plus mineral filler) and adhesive bond between aggregates and the asphalt binder weakens in the presence of water. Therefore, the chemical thermodynamics theory help a great deal on characterizing the adhesive properties of the warm mix asphalt using foaming process. Moisture damage models of asphalt mixtures are presented based on surface and interface theory. Using the capillary rise method and the Sessile drop method, surface energy parameters of aggregate and asphalt are determined respectively. This paper presented comparative results for two types of aggregates (limestone and sandstone) and two asphalt binders (control hot mix asphalt and foamed asphalt) for a total of four different mixtures. The water sensitivity of four mixtures are ranked. The results indicates that surface energy of foamed asphalt is almost equivalent to that of control hot mix asphalt, and limestone has a higher surface energy and a better water resistance compared to sandstone. It is found that foamed asphalt using limestone has good water resistance.
Unmodified and SBS modified asphalt binders respond differently to foaming as well as the amount of water used for foaming. Unmodified binder performs better in rutting with 1% of foaming water while modified one performs better with 3% of water. Unmodified binder performs better in low temperature with 1% of water while modified one performs better with 3% of water. 1% of water reduces unmodified binder's temperature sensitivity (TS) but foaming increases the TS of modified binder. Unmodified binder performs better in fatigue with 1% of water while modified one performs better with 2–3% of water. a b s t r a c t It has been shown from existing studies that foamed Warm Mix Asphalt (WMA) can effectively improve the workability of asphalt mixtures at relatively low temperature. However, there is limited research into the influence of the amount of water used to foam WMA on the rheological properties and performance-related characteristics of the foamed asphalt. In this study, different amount of water was used to foam non-modified and styrene–butadiene–styrene triblock copolymer (SBS) modified bitumen to create foamed bitumen specimens. They were subsequently tested for high temperature performance, low temperature performance, temperature sensitivity, and fatigue resistance properties. Test results indicate that water content in the foamed asphalt has significant impacts on its various properties and there is an interactive effect between asphalt type and water content. In general, it appears that better results can be achieved if one per cent of water is used to foam the unmodified asphalt, and three per cent of water is used to foam the modified asphalt. The findings may assist controlling experimental variations and improving foamed WMA production.
Use of Foamed Asphalt and Foamed Bitumen for Recycled Asphalt Mixtures: A Review
Civil Engineering and Architecture, 2024
The recycling of both worn-out asphalt layers and the entire pavement has led to the development of innovative materials that can be incorporated into conventional asphalt mixtures. Within this type of compounds, foamed asphalt and foamed bitumen stand out, not only from the functional aspect, but also from the environmental aspect, since they allow controlling and significantly reducing the placement temperature of the asphalt mix. In this context, this article develops an exhaustive review of the main aspects of the use of foamed asphalt and foamed bitumen for recycled asphalt mix, taking into account the selection of 86 articles referring to the topic, available in the Scopus, Science Direct, Scielo and Google Scholar databases corresponding to the period 1900 to 2022. It was possible to learn about the application of foamed asphalt and foamed bitumen, its characteristics and properties, its incorporation processes in the mixture, its advantages and disadvantages, its reactions with the different aggregates and their performances in the recovered asphalt mix. Finally, it is concluded that both foamed asphalt and foamed bitumen are highly advantageous due to their properties in recycled asphalt mix, since in addition to greatly reducing the temperature of a conventional mixture, it allows maintaining the same mechanical properties compared to a hot mix asphalt.