Evaluation of Physical Properties of Bituminous Mixtures Modified with Polymer Additives

The road construction industry is concerned with utilizing alternative and sustainable binder materials to aid in the production, placement and increase in the performance of flexible pavements. This research is aimed at evaluating the physical properties of bituminous mixtures modified with PET (Polyethylene Terephthalate), SBS (Styrene-Butadiene-Styrene) and EVA (Ethylene-vinyl Acetate) used as bitumen modifiers. The samples were prepared by heating the base bitumen and each polymers to their respective melting points to facilitate the miscibility of the materials; the base bitumen and each polymers were mechanically mixed together with a blending speed of 2000 ± 10 rpm for an hour. Penetration, ductility, softening point, flash and fire point and water in bitumen tests were performed to relevant standard specificationson bitumen and PMB (Polymer Modified Bitumen) with polymer composition varied from 10% to 50%. The penetration test result showed that polymers have hardening effect on bitumen; this was evidenced by the reduction in the penetration values of PET modified bitumen from 51 to 57 decimillimetre (dmm), 59 to 55 dmm for SBS modified bitumen and 68 to 59 dmm for EVA modified bitumen for all the percentage compositions. The PMB showed improved stiffening which was demonstrated by increase in the softening point of the PMB; the softening point of PET modified bitumen increased from 540C to 670C. Likewise, the softening point of SBS modified bitumen increased from 560C to 700C and the softening point of EVA modified bitumen also increased from 550C to 600C for all the percentage polymer compositions. The improvement in the water resistant capability ofthe PMB was confirmed by the reduction of moisture content of bitumen on addition of polymers from 3% for bitumen to 1.1% which is the least moisture content recorded at 50% composition of SBS modified bitumen.

Keywords:

Physical properties , polymer additives , bitumen , bituminous mixture