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Mix design considerations of foamed bitumen mixtures with reclaimed asphalt pavement material

Kuna, Kranthi; Airey, Gordon; Thom, Nick

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Kranthi Kuna

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Professor of Pavement Engineering Materials

Assistant Professor


In the present work, a mix design parametric study was carried out with the aim of proposing a practical and consistent mix design procedure for foamed bitumen mixtures (FBMs). The mix design parameters that were adopted in the study are mixing and compaction water content (MWC), compaction effort using a gyratory compactor and aggregate temperature. This parametric study was initially carried out on FBMs with virgin limestone aggregate without reclaimed asphalt pavement (RAP) material and a mix design procedure was proposed. This proposed methodology was also found to apply to FBMs with RAP. A detailed consideration was also given to characterising the RAP material so as to understand its contribution to the mechanical properties of FBMs. Optimum MWC was achieved by optimising mechanical properties such as indirect tensile stiffness modulus and indirect tensile strength (ITS-dry and ITS-wet). A rational range of 75–85% of optimum water content obtained by the modified Proctor test was found to be the optimum range of MWC that gives optimum mechanical properties for FBMs. It was also found that the presence of RAP influenced the design foamed bitumen content, which means that treating RAP as black rock in FBM mix design is not appropriate. To study the influence of bitumen and water during compaction, modified Proctor compaction and gyratory compaction were employed on mixes with varying amounts of water and bitumen. By this, the work also evaluated the validity of the total fluid (water + bitumen) concept that is widely used in bitumen–emulsion-treated mixes, and found it not to be applicable.


Kuna, K., Airey, G., & Thom, N. (in press). Mix design considerations of foamed bitumen mixtures with reclaimed asphalt pavement material. International Journal of Pavement Engineering,

Journal Article Type Article
Acceptance Date Nov 17, 2015
Online Publication Date Jan 4, 2016
Deposit Date Mar 17, 2017
Publicly Available Date Mar 17, 2017
Journal International Journal of Pavement Engineering
Print ISSN 1029-8436
Electronic ISSN 1029-8436
Publisher Routledge
Peer Reviewed Peer Reviewed
Keywords Bitumen treated mixes, Mixing and compaction water content, Reclaimed asphalt pavement, Mechanical properties, Volumetrics, Water-bitumen interaction
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Additional Information This is an Accepted Manuscript of an article published by Taylor & Francis in International Journal of Pavement Engineering on 4th January 2016, available online:


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