Performance based evaluation of lime addition methods in hot mix asphalt

The benefits of using hydrated lime as an additive in asphalt concrete are well known. When added to asphalt concrete mixtures hydrated lime shows the beneficial effects of filler, while also improving resistance to moisture damage. Even with the great deal of literature and experience extolling the benefits of hydrated lime, little research exists regarding the impact of hydrated lime on the fundamental behavior and performance of asphalt concrete mixtures. This paper presents findings of the impact of lime introduction method on the volumetric optimums and the fundamental behavior and performance of asphalt concrete mixtures. The behavior of various mixtures is assessed with the dynamic modulus tests and through characterization tests for the viscoelastic continuum damage model, a mechanistically based material model. Permanent deformation performance assessment is made with triaxial repeated load permanent deformation tests. From the experimental investigation it is found that the method of lime introduction can have an important effect on the optimum volumetric asphalt content. Regarding mixture performance it is found that hydrated lime has a minimal impact on the dynamic modulus of the mixtures in this study. Conversely, it is found that hydrated lime has a positive effect on both the permanent deformation and fatigue cracking performance of asphalt concrete mixtures. The magnitude of this positive impact is shown to be affected by the method used to introduce hydrated lime into the mixture.