Book Description

Rates and causes of asphalt hardening were investigated to determine its effect on pavement performance. Hardening of 46 New York State pavements, ranging in age from construction through 16 years of service, was studied by recovering asphalt cements by the Abson method and performing penetration tests on recovered material. It was found that early hardening is not a problem in New York State and that penetrations of asphalt cement recovered from top courses correlate with pavement performance (although penetration decreases with time, each pavement differs in rate of hardening). A regression analysis demonstrated the significance of the following factors (in order of importance) in the mechanism of asphalt hardening: percent voids in the mineral aggregate filled with asphalt cement, bitumen index and average annual daily traffic. A brief review of the state of the art in testing for asphalt cement properties is appended.