Study of the effect of four warm mix asphalt additives on bitumen modified with 15% crumb rubber

Due to a growing concern over global warming, the bituminous mixture industry is making a constant effort to diminish its emissions by reducing manufacturing and installation temperatures without compromising the mechanical properties of the bituminous mixtures. The use of mixtures with tyre rubber has demonstrated that these mixtures can be economical and ecological and that they improve the behaviour of the pavements. However, bituminous mixtures with a high rubber content present one major drawback: they require higher mixing and installation temperatures due to the elevated viscosity caused by the high rubber content and thus they produce larger amounts of greenhouse gas emissions than conventional bituminous mixtures.This article presents a study of the effect of four viscosity-reducing additives (Sasobit®, Asphaltan A®, Asphaltan B® and Licomont BS 100®) on a bitumen modified with 15% rubber. The results of this study indicate that these additives successfully reduce viscosity, increase the softening temperature and reduce penetration. However, they do not have a clear effect on the test for elastic recovery and ductility at 25 °C.

► The four organic additives studied reduces the viscosity of a binder modified with 15% rubber.
► The theoretical reduction of the manufacturing temperature is smaller in bitumen with 15% rubber than in pure binders.
► Additives into the binder modified with 15% rubber causes the penetration to decrease and the softening point increase.
► It was not possible to clearly establish the effect of the organic additives on the elastic recovery test.
► The force-ductility test at 25 °C does not seem to be reliable due to the rubber particles that produce premature breakage.