The Effect of Styrene-Butadiene-Styrene Modification on the Characteristics and Performance of Bitumen

Summary. In order to cover the effect of styrene-butadiene-styrene (SBS) modification on the characteristics of bitumen, two types of bitumen, one plain bitumen, and one polymer modified bitumen produced with the plain bitumen as base material were characterized in terms of chemical composition, microstructure, micromechanical properties, and thermoanalytical behavior. In order to determine the complex chemical composition of bitumen, elemental analysis, gel permeation chromatography, and the Iatroscan method were employed. Microstructure and micromechanical properties were determined using an environmental scanning electron microscope and the nanoindentation technique. Modulated differential scanning calorimetry was used to determine phase-change temperatures and endo/exotherms associated with molecular movement. The addition of SBS leads to different rheological behavior over the whole service temperature range. This is reflected in bitumen chemistry by differences in elemental composition and molecular weight distribution with much higher M _w values for the modified bitumen. Accordingly, the polymer leads to a shift in molecular fractions. Electron microscopy reveals two distinct phases building up the bitumen microstructure. The chosen mode of quantification leads to similar material parameters for both bitumens, which is explained by the use of the same base material. In contrast, nanoindentation delivers viscosities in the micro-range corresponding to large-scale rheological properties. Modulated differential scanning calorimetry indicates two glass transitions corresponding with two material phases also confirmed by other experiments. Due to modification, these glass transitions depart from each other and the amount of the two material phases changes, correlating with the shift in molecular fractions observed in Iatroscan analyses.