A primary contributor to asphalt deterioration is the reaction of the asphalt with atmospheric oxygen, causing asphalt hardening and embrittlement.  The Inverse Gas Liquid Chromatography (IGLC) technique was developed to study the aging characteristics of asphalt by determining the polar interactions of chemical functional groups.  Oxidative aging of the asphalt in the column allows us to measure the change in chemical functionality over an accelerated period.  

In the IGLC technique, the asphalt serves as the stationary phase on a gas chromatographic capillary column.  The chemical functionality of the asphalt is studied by observing the retention characteristics of volatile test compounds with known functional groups as they pass through the column and interact with the chemical functionality of asphalt. 

IGLC retention data for the test compound phenol on asphalts have been correlated with road service (Zaca-Wigmore road test) and with Weather-O-Meter durability and show a relationship with the tendency to form cracks.  Western Research Institute is currently working with state DOTs to monitor comparison pavement validation sites where only the crude oil source used to produce asphalts is varied.  These sites provide a source of initial hot mix samples where actual performance can be followed with time.