Foamed bitumen: an alternative way of producing asphalt mixtures

With the constant need to improve and make the production of asphalt mixtures more sustainable, new production techniques have been developed, the implementation of which implies the correct knowledge of their performance. One of the most promising asphalt production techniques is the use of foamed bitumen. However, it is essential to understand how this binder will behave when subject to the expansion process. The loss of volume of the foamed bitumen could be translated by a decay curve, which allows to determine the ideal temperature and water content added to the bitumen in order to assure adequate conditions to the mix the bitumen with the aggregates. On the present study, a conventional 160/220 pen grade bitumen was tested by using different temperatures and water contents, and it was concluded that the optimum temperature for the production of foamed bitumen (with the studied bitumen) is 150 ºC, which corresponds to a viscosity of 0.1 Pa.s. The water content mostly influence the half-life of the bitumen foam, resulting in quicker volume reductions for higher water contents.This work was funded by FEDER funds through the Operational Programme for Competitiveness Factors – COMPETE, given to the project “Energy Efficiency and Environmental Design of Bituminous Mixtures to Reduce Emissions of Greenhouse Gases” (QREN-SI 090528), of the company ELEVO Group, which was carried out in cooperation with the University of Minho. Thanks are also due to the Foundation for Science and Technology (FCT) for funding allocated through the PhD Scholarship SFRH/BD/85448/2012, and to the companies GALP and ELEVO Group., who provided the binder and the reclaimed asphalt used in this study.