Direct tensile test evaluation and characterization for mechanical and rheological properties of polymer modified hot mix asphalt concrete

Using polymer to modify asphalt binder for better performance has become popular in pavement engineering, for which to evaluate the effect of polymer addition on the properties of the asphalt concrete is essential for mix design. Conventional mechanical test methods, primarily using bending of beams and indirect splitting, are not only materially and timely costly and labor intensive but also provide no direct information for the viscoelastic and rheological characteristics of the materials. This paper reports a study using direct tensile test (DTT) to evaluate the effect of polymer on both mechanical and rheological properties of modified asphalt concrete. Two types of polymers, which are styrene-butadiene-styrene (SBS), and a mixture of SBS and polyvinyl chloride (PVC), were investigated on two mixes using fine and coarse aggregates, respectively. It has been found that SBS generates improvement for both mechanical and rheological properties of hot mix asphalt concrete. However, using a hybrid mixture of SBS and PVC shows that PVC can further improve the mechanical properties, but deteriorate the toughness of the asphalt concrete. At the end, a simple quadric polynomial model has been proposed to characterize the combined SBS and PVC effects for the sake of the guidance for mix design.