Synthesis of Asphalt Binder Aging and the State of the Art of Antiaging Technologies

Abstract

Abstract:Aging is the accumulation process of diverse detrimental changes in molecular structures with advancing age. Resistance to aging is termed durability. Complex molecular systems such as asphalt binder need to be protected against aging. In this paper, a state-ofthe-art review of anti-aging technologies used to prohibit or to rejuvenate the aged asphaltic materials is provided. The kinetics of molecular structures during aging and the group of molecules affected mainly are discussed. The latest developments on anti-oxidation and rejuvenation technologies are given as well showing the impact of anti-aging technologies for the asphalt binder. INTRODUCTIONThe transportation industry consumes approximately 32.6% of the total energy produced in the European Union and almost 28% in the United States. In parallel with the increasing cost and the strong global demand for low prices of the paving materials and operations, the rapid aging of asphalt pavements due to the aggressive environmental conditions is becoming a pragmatic concern for the whole transportation industry. Avoiding the aging of asphalt binder or preventing the undesirable effects of ultimate degradation of asphalt mixes after certain time are among the major topics in which governmental authorities and infrastructure contractors have focused. Strategies, such as preventive maintenance techniques and reconstructive treatments of asphalt pavements, have been deployed in the last years to deal with the aging phenomena of asphaltic materials. Also, the utilization of additives as the countermeasure to prohibit aging of asphaltic materials (i.e., anti-oxidants) and to restore materials' characteristics (i.e., rejuvenators) shows significant benefits in these efforts. Asphalt binder (AB) is composed of an extremely large number of different types of organic molecules ranging from paraffins to alkyl polyaromatics containing heteroatoms of nitrogen (≤ 2%), oxygen (≤ 2%), sulphur (≤ 6%) and traces of metals such as vanadium and nickel. These molecules are separated in categories based on the chemical reactivity and the polarity of organic molecules. The dispersion of polar organic molecules in a medium of less polar molecules and their interaction are highly associated with the performance-related properties of ABs and their susceptibility under oxidation. When the material is oxidized, the state of molecular dispersion within the binder alters and new polar molecules are produced.Several studies have reported on the oxidation chemistry of AB, the main factors influencing aging and how aging can be addressed using chemical additives and anti-aging technologies. In this paper, focus was given to combine information of the most valuable researches which were validated for several times for the aged ABs and the anti-aging technologies. The current and concise state-of-the-art review on aging and anti-aging is provided with highlighting the chemistry of AB and the chemical interaction of anti-aging additives on them.

Chemical and Rheological Evaluation of Aged Lignin-Modified Bitumen

“…It may require a longer exposure time for the lignin-modified binders to display the same worm structures. 1.3774 g/cm 3 1.5029 g/cm 3 147.06 m 2 /g 65.05 m 2 /g Regarding the microstructural morphology of lignin-modified bitumen, the worm structures of fresh and aged binders (i.e., Bref_F, Bref_A, BL10, and BL10 A; see Table 1) were obtained by ESEM, as shown in Figure 3a,b. In particular, all fresh binders had a relatively clear slim worm structure.…”

“…Bitumen is a hydrocarbon residue produced from oil refining and comprises a plethora of different organic molecules causing its vulnerability to environmental conditions [1]. Currently, the rising cost of bitumen, together with the fact that asphalt production is one of the largest energy consumers, globally encourages the use of alternative systems to replace petroleum-based binders to enhance the quality of pavement materials.…”

Effect of laboratory aging on chemistry and rheology of crumb rubber modified bitumen

“…This socalled chemo-mechanics correlation will be beneficial to understand the dependence of mechanical properties of binders on their chemical composition. While ketone formation is well correlated to asphaltene formation on oxidation, sulfoxide formation does not contribute to asphaltene formation because sulfoxide derived from the oxidation of sulfides are less polar than asphaltene [1]. Asphaltenes have been proven to be primarily responsible for the viscosity increase (stiffening effect) on aging.…”

“…Bitumen, as a refined residue from the distillation process of crude oils, is composed of an extremely large number of different organic molecules, which makes it susceptible to the changes of environmental conditions [1]. The aging of bitumen affects nearly all critical aspects of asphalt paving materials, which makes aging a fundamentally important factor that influences the performance and durability of asphalt pavements.…”

Evaluation of Organosolv Lignin as an Oxidation Inhibitor in Bitumen

“…The use of lignin is not limited only as modifier or substitute of bitumen but it can be incorporated as an oxidation inhibitor as well to minimize the aging potential and to improve the durability of binders [5]. Particularly, during oxidative aging, oxygen reacts with molecules present in bitumen, producing polar compounds, principally ketones and sulfoxides and causing an increase in the portion of asphaltenes.…”