Effects of polymer additives on bituminous mixtures

The laboratory investigation described in this paper focuses on the effects of polymers as additives for bituminous mixtures. Three dosages (3%, 6% and 9% by weight of bitumen) of EVA and LDPE polymers were used. The investigation was divided into two main phases. The first one focused on a comparison between mixtures to which polymers were added and a modified bitumen-bound mixture. The comparison was performed by observing constructability, volumetric and mechanical performances (e.g. dynamic moduli). The second phase aimed at evaluating the effects of such polymers on the performance of the corresponding mixtures at in service temperatures by means of simulative tests concerning stiffness master curves, fatigue life and rut resistance. In the second phase, the modified bitumen-bound was not investigated. Both phases also include investigations on a standard bitumen-bound mixture. Results of the first phase revealed that polymers guarantee the same, if not better, performances than modified bitumen on the corresponding bituminous mixtures. Results of the second phase showed that polymers increase the mixtures' performances at in-service temperatures. In particular, polymers reduce mixtures' Stiffness at low temperatures, increase fatigue life at intermediate temperatures and reduce rutting deformations at high temperatures.