Molecular dynamics study of oxidative aging effect on asphalt binder properties

Although already known for a long time, hydrated lime (HL) attracted a strong interest as an asphalt additive during the 1970s in the USA, when moisture damage and frost became some of the most pressing pavement failure modes of the time. Given its extensive use in the past 40 years, HL is known to be more than a moisture damage additive: it is an “active filler” that also reduces the chemical ageing of the bitumen and stiffens the mastic more than a normal mineral filler above room temperature. These properties impact durability, and HL is now seen as an additive that increases asphalt mixture durability. This article is a literature review on the fundamentals of the effect of HL on asphalt mixtures. The reasons for it being so effective lie in the strong interactions between both the aggregate and the bitumen and a combination of four mechanisms, two on the aggregate and two on the bitumen. HL modifies the surface properties of the aggregate, allowing for the development of surface composition and rough...

https://www.tandfonline.com/doi/pdf/10.1080/14680629.2012.743669

The mechanisms of hydrated lime modification of asphalt mixtures: a state-of-the-art review

Understanding the bitumen ageing phenomenon: A review

Field aging effect on chemistry and rheology of asphalt binders and rheological predictions for field aging

This RILEM round robin study with nine participating laboratories investigated bitumen ageing, its effect on chemical properties and its reproducibility. The impact of temperature used for short-term (RTFOT) binder ageing on the combined short- and long-term (PAV) aged samples was investigated; thereby the effect of reduced mixing temperature such as those relevant for warm mix asphalt technologies on long term ageing was examined. Four 70/100 penetration graded bituminous binders from different sources were selected. In addition to the standard RTFOT temperature of 163 °C, two additional temperatures, 143 and 123 °C were used. The Fourier transform infrared spectroscopy (FTIR) analysis was carried out using an integration method which considers the area below the absorbance spectrum around a band maximum using baseline and tangential approaches. A statistical investigation into the reproducibility of FTIR spectra analysis based on the accumulated data was done. To assess the reproducibility, the coefficient of variation (CV) was taken as a benchmark parameter. Carbonyl and sulfoxide indices were calculated using different baseline correction methods and tangential and baseline integration, respectively. It was shown that the tangential method was not influenced by the applied baseline correction. However, in all considered cases, the tangential method led to significantly worse reproducibility (CVs ranging from 20 to 120%) compared to the baseline method. The sulfoxide indices calculated by both methods were not affected by the baseline correction method used. Impacts of changes in the short-term ageing temperature on short- or long-term aged samples could not be found whereas differences between different binder sources could be detected. RTFOT temperature and therefore mix production temperature had a stronger impact on the formation of sulfoxide structures than for carbonyl structures. The findings from this study show the most reproducible of all considered methods when more than one laboratory is providing FTIR data.

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FTIR spectral analysis of bituminous binders: reproducibility and impact of ageing temperature

The correlation between asphalt viscosity increase on oxidative aging and the carbonyl compounds formed (almost exclusively ketones) has been well established; however, the effect of sulfoxide formation on physical properties during age hardening has received little attention. Evidence is presented in this paper that shows that the alcohols, which are formed concurrently with the sulfoxides from the same hydroperoxide precursors as the ketones, have a similar effect on asphalt viscosity increase as does the ketones. These alcohols are the main contributors to oxidative age hardening of high sulfur asphalts. Analysis of the kinetic data for ketone and sulfoxide formation during asphalt oxidation also provides additional evidence for the validity of the dual asphalt oxidation mechanism previously reported.

J. Claine Petersen

Papers

Asphalt Oxidation Mechanisms and the Role of Oxidation Products on Age Hardening Revisited