EVALUATION EFFECT OF PARTICLE SIZE ANDCONCENTRATION OF POLYMER STYRENE BUTADIENESTYRENE (SBS) ON THE ENGINEERING PROPERTIES OFASPHALT MIXTURE

Scientists and engineers are constantly trying to improve the performance of asphaltconcrete pavements by the modification of the asphalt binder. Polymer-modified asphaltmixtures have been used for many years to reduce the amount and severity of distress and extendthe service life of hot mix asphalt (HMA) pavements. The polymers have acceptable effects onasphalt mixes in low and high temperature due to increasing the resistance to fatigue cracking,rutting (permanent deformation) and thermal cracking. The major objective of this research is toevaluate the effect of polymer on the properties of the Hot Mix Asphalt (HMA). One asphaltcement grade (40-50) from Al-Daurah refinery, one type of locally available polymer styrenebutadiene styrene (SBS) with three various particle sizes. Three sizes are obtained from sievinganalysis at sieves (No16 (1mm), No9 (2mm) and No5 (4mm)) have been used with threepercentages for each size. These percentages are (1, 2.5 and 4) % for SBS by weight of asphaltcement. Each size of polymer is blended with asphalt cement by wet process of blending times60 minutes for a suitable range of temperatures at (180ºC). The experimental works showed thatall polymer-modified mixtures have (stability, indirect tensile strength and rutting resistance)higher than control asphalt mixtures, in about (50-107) %, (11-32) % and (33-47) %),respectively, dependent on different particle sizes of polymer and polymer concentration underpredicted suitable blending time. It can be concluded that the small particle sizes of styrenebutadiene styrene (SBS No16) give better properties of pavement. Therefore, the addition of(2.5% SBS No16) to asphalt mixtures showed better improvement on the performance propertiesof pavement modified with polymer, in which the referred percentage represents the optimumpercent of concentration for blending polymer.KEY WORDS