Comparative study of the effect of sulfur on the morphology and rheological properties of SB‐ and SBS‐modified asphalt

Abstract

ABSTRACT:The modification of asphalt with styrenebutadiene block copolymers and sulfur was studied to elucidate the effect of the molecular characteristics of the polymer, polymer content, and sulfur/polymer ratio on the physical properties of modified asphalts. Two types of styrene-butadiene copolymers were used (SB and SBS), which differed considerably in terms of their chain architecture, average molecular weights, and size and distribution of their polybutadiene and polystyrene blocks, as shown by gel permeation chromatography, infrared spectroscopy, nuclear magnetic resonance, and differential scanning calorimetry. Sulfur/polymer/asphalt blends were prepared by a hot mixing process and characterized by conventional tests, fluorescence microscopy, and rheology. The results revealed that the morphology of the blends is strongly dependent on polymer concentration and sulfur/polymer ratio. In-depth rheological characterization showed that the thermomechanical properties changed considerably upon addition of small amounts of sulfur. Collectively, these results suggest that sulfur increases the compatibility between polymer and asphalt by crosslinking polymer chains. Interestingly, the rheological behavior of blends prepared with a combination of SB and sulfur was similar to that exhibited by blends prepared with SBS either in the presence or absence of sulfur. This is explained by assuming that the addition of small amounts of sulfur to SB-modified asphalt facilitates the formation of an elastomeric network that resembles the one found in SBSmodified asphalt, effectively contributing to asphalt reinforcement. Nonetheless, the exact dosage of sulfur must be carefully controlled to prevent gel formation.

A review of the fundamentals of polymer-modified asphalts: Asphalt/polymer interactions and principles of compatibility

“…The same evidence for vulcanization was shown by Jin et al [242], who presented the curing curves obtained in a rheometer at different temperatures and PS contents in asphalt/PS/SBS/sulfur blends as well as the S values demonstrating the beneficial effect of sulfur for storage stability. Another indirect evidence for vulcanization was reported by Martınez-Estrada et al [243], who modified asphalts by using either SB or SBS copolymer and performed a detailed rheological characterization of the blends. Among the long list of reported rheological data, the main observation that supports vulcanization is that the rheological behavior of SBS-modified asphalts (with or without sulfur) is far different from that of SB-modified asphalts without sulfur, while it is fairly well reproduced by the same blends after the addition of relatively small amounts of sulfur.…”

Sulphur Utilization in Asphaltic Concrete Pavements

“…Consequently, phase separation during the hot storage is expected to decrease. Besides, sulphur was seen to pave the way of the formation of three-dimensional structures reinforcing bitumen (Martínez-Estrada et al 2010). Hence, it can be claimed, with no hesitation, that sulphur as an additive advances the rheological behavior of not only pure bitumen but PMB as well.…”

Investigation on compatibility and microstructure of PCBs‐modified asphalt

“…[33][34][35] The storage stability of modified asphalt with chemical reaction is better than that of samples with nonchemical reaction. [33][34][35] The storage stability of modified asphalt with chemical reaction is better than that of samples with nonchemical reaction.…”