مطالعه رفتار ويسكوالاستيك آميخته هاي قير- پلي اتيلن

Viscoelastic behavior of bitumen, recycled polyethylene (RPE) and RPE-modified bitumen were investigated in a wide frequency range. Based on microscopic observation, the RPE particles are suspended in the bitumen matrix. The radius distribution of particles in the bitumen is 5-25 um and for washing particles in the range of 1 to 5 um. In addition, the RPE particles are completely expanded in the bitumen. This morphology is attributed to the physical interactions and it leads to formation of physical structures like clusters and physical networks. RPE in bitumen is appeared as two mixture phases. Viscoelastic behavior of RPE-modified bitumen was considered as a two-phase composites which the polymer particles were dispersed in bitumen matrix. It is observed that the rheological and viscoelastic properties change largely with addition of only 1% RPE. On the other hand, the rheological properties of RPE-modified bitumen change largely by aging of bitumen. This has been attributed to absorption of residual oil by polymer particles and the interactions between asphalt constituent and polymers. As a consequence, the changes in rheological properties of bitumen during mixing should be considered separately. For this reason, the rheological data is measured on polymer modified as well as the blank bitumen (called Shahed) with the same thermomechanical history as reference. Firstly, the shear modulus curves were obtained in the wide range of frequencies. Then the equations in the fourth order were fitted in the experimental results. These equations were used for calculation of the unmeasured points in the intervals of the experimental results. Christensen and Loʹs model was used to predict the viscoelastic behavior of RPE modified bitumen. This model is based on a representative element volume (REV) accounting for a morphology analysis. Based on the use of the mechanical model and the experimental results, the viscoelastic behavior of RPE-modified bitumen depends not only on the relative amount and the polymer distribu-tion within the matrix, but also on the changes in the mechanical properties of bitumen in the mixing process.