Effect of Polyolefin Modified Bitumen on Marshall Stability

Abstract

It is possible to improve the performance of the hot mix asphalt (HMA) by improving the properties of the materials (aggregate, bitumen) used in the HMA or by the addition of some special materials. In this study; polypropylene (PP) and high density polyethylene (HDPE) waste plastics were co–pyrolyzed at a temperature range of 300–350 °C. 2, 4, 5 and 6 % modified bitumen were made by using the solid product (char–additive) obtained from co–pyrolysis and pure 50/70 penetration grade bitumen. RV (rotational viscometer) tests were applied to pure and modified bitumens at different temperatures (60–165 °C) and the optimum rate of PP–HDPE additive was determined to be 5 %. Then; two different HMA sample series were prepared with Marshall apparatus using pure and 5 % PP–HDPE modified bitumen. For Marshall Mix design, sample series were formed at bitumen rates 3.5; 4; 4.5; 5 and 5.5 % and four HMA samples were produced at each bitumen rate. The samples were weighed in water, dry and saturated surface–dry. The heights of the samples were measured and the Marshall stability and flow values were determined by applying a load at a certain speed (50 mm/min). As a result; compared to the pure HMA, it was observed that the Marshall stability of the modified HMA increases between about 8.5 and 13 %.