Laboratory investigation on mechanical performance of cold foamed bitumen mixes: Bitumen source, foaming additive, fiber-reinforcement and cement effect

Foaming additives (FA) have been developed for improving foaming characteristics on bitumens which do not comply with minimum requirements for producing foamed bitumen mixes (FBM). In addition, fiber-reinforcement (FR) inclusion on hot mix asphalt has shown important improvement on the mix mechanical properties. For instance, some reported benefits of FR addition include enhancements on viscoelastic behavior, better rutting resistance and superior fatigue performance. However, in spite of these potential benefits and advantages from both FA and FR, very limited experience is available in the literature concerning the effect of these technologies on foamed cold mixes properties. This paper presents the results of a laboratory investigation on cold foamed recycled mixes and the effect on the mechanical properties of various additives. Three bitumen sources, one FA, two different FR types and Portland cement active filler were evaluated. The mechanical properties evaluation included dynamic modulus and indirect tensile strength of dry and conditioned specimens. The addition of FA had very little effect on the mechanical performance with respect to mixes with the same bitumen but without FA. The FR inclusion resulted in increased dynamic modulus at some temperatures. Portland cement used as active filler provided significant increments in both modulus and strength, although the greater benefits were observed on moisture resistance.