PAVEMENT PERFORMANCE ANALYSIS OF THE ILLINOIS INTERSTATE HIGHWAY SYSTEM. INTERIM REPORT

The Illinois Interstate highway system was mostly constructed between 1957 and 1980 and consists primarily of continuously reinforced concrete pavement (CRCP) and jointed reinforced concrete pavement (JRCP). Extensive pavement design, traffic and performance data were obtained from 3228 one-directional miles of Interstate highway. Truck traffic has increased tremendously since 1957. The mean yearly 18-kip ESAL (one-direction, outer lane) application rate averages over all pavements has increased from about 300,000 to 1,200,000 over this time period. The annual compound growth rate of accumulated ESAL has been over 8%, far more than expected. Survival curves showing the percent of construction sections overlaid as a function of age and ESALs were developed for each pavement type and design. The average life span until 50% of the sections were rehabilitated was 21 years, after carrying about triple their design ESALs over that time period. The thickness of CRCP had a major effect on the number of ESALs carried. Durability cracking (D cracking) of PCC aggregates severely affects CRCP performance, shortening the average life by five years or more. The average life of JRCP was not shortened significantly by D cracking (although a few sections developed severe D cracking which shortened their life considerably). The average 8 in. CRCP carried about the same 18-kip ESAL as the average 10 in. JRCP, however, non D cracked 8 in. CRCP carried more ESALs than 10 in. JRCP.