The paving industry is currently demanding polymer modified bitumens (PMBs) with enhanced in-service performance and low enough viscosity at lower application temperatures. With this aim, this study focuses on the use of ethylene vinyl acetate (EVA) copolymers with low melting temperatures and explores the effect on the desired properties of the vinyl acetate (VA) content and Melt Flow Index (MFI). To that end, binders were prepared from EVA copolymers having varying VA contents from 7 to 33 wt.%, and MFI from 2 to 800. A comprehensive characterization based on viscous flow curves, dynamic shear temperature sweeps, standardized technological tests, differential scanning calorimetry (DSC) and optical microscopy analysis was conducted on EVA-binders with 5 and 7.5 wt.% EVA. Low VA contents proved to endow bitumen with improved performance at medium-high in-service temperatures. Interestingly, binder viscosity at 135ºC decreased with increasing the MFI, regardless the selected VA content. This means that tailored PMBs can be designed with both improved in-service performance at medium-high temperatures and reduced viscosity to facilitate polymer-bitumen mixing, mineral coating and asphalt mix laydown/compaction at lower temperatures.This research is a part of the Marie Curie Initial Training Network (ITN) action, FP7 - PEOPLE-2013-ITN. This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement number 607524
6 May 2019 in International Journal of Renewable Energy Development
High energy consumption and environmental risks are both associated to the use of hot asphalt mixes. In response to the need of more sustainable pavements, the modification of bitumen with low melting point EVA copolymers is investigated. Firstly, different modified binders containing EVA with varying VA contents (and so different crystalline fractions and melting temperatures) and Melt Flow Index (MFI) values were investigated. In the second stage, emulsification was implemented, in which the above EVA modified bitumen was suspended in the form of micro-size droplets in aqueous phase, in the presence of a surfactant. The results suggest that an optimum balance between VA content and MFI value will improve the binder rheological performance at medium-high in-service temperatures as well as its workability, and will facilitate its emulsification. Additionally, the binder viscosity is tremendously reduced after its emulsification, which allows mixing to be performed at much lower temperature, so reducing both energy consumption and environmental risks
Oil-in-water bitumen emulsions stabilized by biobased surfactants such as lignin are in line with the current sustainable approaches of the asphalt industry involving bitumen emulsions for reduced temperature asphalt technologies. With this aim, three lignins, derived from the kraft pulping and bioethanol industries, were chemically modified via the Mannich reaction to be used as cationic emulsifiers. A comprehensive chemical characterization was conducted on raw lignin-rich products, showing that the kraft sample presents a higher lignin concentration and lower molecular weight. Instead, bioethanol-derived samples, with characteristics of non-woody lignins, present a high concentration of carbohydrate residues and ashes. Lignin amination was performed at pH = 10 and 13, using tetraethylene pentamine and formaldehyde as reagents at three different stoichiometric molar ratios. The emulsification ability of such cationic surfactants was firstly studied on prototype silicone oil-in-water emulsions, attending to their droplet size distribution and viscous behavior. Among the synthetized surfactants, cationic kraft lignin has shown the best emulsification performance, being used for the development of bitumen emulsions. In this regard, cationic kraft lignin has successfully stabilized oil-in-water emulsions containing 60% bitumen using small surfactant concentrations, between 0.25 and 0.75%, which was obtained at pH = 13 and reagent molar ratios between 1/7/7 and 1/28/28 (lignin/tetraethylene pentamine/formaldehyde).