Characterization of Crumb Rubber Modifiers after Dispersion in Asphalt Binders

Abstract

Blending ground crumb rubber (CR) with the asphalt binder is an economical and sustainable method of binder modification. The objective of this paper was to evaluate the interaction between the asphalt binder and the three CR types at 170 and 190 °C. The three CR types, ambiently ground, cryogenically ground, and Ecorphalt (E-rubber), were blended with a Louisiana conventional PG 67-22 asphalt at two temperatures, 170 and 190 °C. The composition of the CR before and after treatment with asphalt was studied using thermogravimetric analysis. Gel permeation chromatography was used to study the molecular weight changes to the asphalt before and after rubber treatment. Fourier transform infrared spectroscopy was used to study the aging characteristics of the CR-modified asphalt binder prepared at the two temperatures. Scanning electron microscopy (SEM) shows the morphology of the rubbers before and after dispersion in the asphalt binder. Performance-grade tests of the CR/asphalt binder blends were used to characterize the rheological properties. E-rubber additive did allow for better dispersion of particles in the asphalt binder at a lower temperature than the other additives evaluated. Ground CR particles were comprised of favorable polyisoprene contents (minimum natural rubber content was 50%) for blending with the asphalt binder. An increase in the blending temperature from 170 to 190 °C resulted in a minimal increase in the favorable polyisoprene contents of CR/asphalt binder blends containing 5 and 10% E-rubber, which is likely to influence performance. Favorable polyisoprene contents of the CR/asphalt blends containing 10% ambiently ground CR did not change with the blending temperature, whereas that of the CR/asphalt blend containing 10% cryogenically ground increased with the blending temperature. The CR particles isolated from asphalt blends prepared at 190 °C were more swollen than those separated from asphalt blends prepared at 170 °C, as measured by SEM. Approximetely 73–87% of the E-rubber particles dissolved in the asphalt binder during blending, confirming that E-rubber had great compatibility with the binder chemistry and, hence, can improve performance.

Effects of polyphosphoric acid (PPA), styrene‐butadiene‐styrene (SBS), or rock asphalt on the performance of desulfurized rubber modified asphalt

“…2,3 So many waste tires are bound to put huge pressure on the environment protection. 4,5 Therefore, how to dispose of these waste tires is an urgent problem in many countries, and it has also been a hot research topic for many years. Studies have shown that using the waste rubber to modify the asphalt binders may be an efficient way to solve this problem.…”

“…It is estimated that around 1.5 billion scrap tires are produced each year and the number is still increasing sharply 2,3 . So many waste tires are bound to put huge pressure on the environment protection 4,5 . Therefore, how to dispose of these waste tires is an urgent problem in many countries, and it has also been a hot research topic for many years.…”

Recycling Tire Rubber in Asphalt Pavements: State of the Art

“…According to Daly et al [44], most of the reported studies on the influence of synthetic crumb According to Wang et al [39], the asphalt-rubber interaction highly depends on time and mixing temperature. Other studies also reported that the use of recycled tire rubber waste in asphalt mixtures lowered thermal susceptibility [2,40], reduced penetration, enhanced the softening point temperature, and, as a result, increased the stability of the asphalt mixtures [41,42].…”

“…According to Daly et al [44], most of the reported studies on the influence of synthetic crumb rubbers on asphalt binder have focused on factors such as crumb rubber particle size, rubber concentration, and blending temperature. On the other hand, fewer studies have investigated the effect of rubber composition on asphalt binder properties.…”

Functionalization of Crumb Rubber Surface for the Incorporation into Asphalt Layers of Reduced Stiffness: An Overview of Existing Treatment Approaches

“…To counteract this phenomenon, several methods aiming to control the swelling behavior of rubber exist. The addition of chemicals to the mixture [13,14], the possible devulcanization [15][16][17][18] or, last but not least, the surface treatment of the CR employing physical or chemical procedures [1,[19][20][21][22][23] are some of the most frequent solutions. The rubber's surface treatment represents an evolving method, preferably used when the dry incorporation method is adopted.…”