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The molecules present in a given asphalt cement binder can be classified into three groups according to their size; large molecular size (LMS) group, medium molecular size (MMS) group and small molecular size (SMS) group. The balance between the relative amounts of these molecules is an important attribute to the asphalt physical characteristics, durability, performance in paving mixtures and overall value as a paving material.
This paper presents a study in which the changes in molecular size distribution and consistency, of a given asphalt, caused mainly by oxidation during the thin film oven test (TFOT) are investigated.
Samples of asphalt cement with the same consistency were exposed to various levels of oxidation (specific periods of time during the TFOT) and then characterized by means of consistency tests (penetration and viscosity). These samples were also characterized employing the high pressure liquid chromatography in the gel permeation mode referred to as the high pressure gel permeation chromatography (HP-GPC).
It was concluded that the artificial weathering of the asphalt cement binder (used in this study) resulted in a significant increase in LMS percentage associated with a significant decrease in MMS and SMS percentages. Regression analyses provided relationships between the asphalt binder consistency (penetration and viscosity) and the relative percentages of LMS, MMS and SMS.
Molecular Size Distribution, Aging, Oxidation, Chromatography, Asphalt Cement
UNDP Advisor, Ministry of Communications, Riyadh,