ASPHALT DURABILITY CORRELATION IN IOWA

Abstract

EIGHT ASPHALT CEMENTS AND PAVING PROJECTS USING THESE ASPHALTS WERE EVALUATED RELATIVE TO THEIR CHANGES IN RHEOLOGICAL AND CHEMICAL PROPERTIES IN PAVEMENT SERVICE FOR AS LONG AS 48 MONTHS. CORRESPONDING CHANGES IN THESE ASPHALTS OF THE SAME PHYSICAL AND CHEMICAL PROPERTIES WERE DETERMINED DURING LABORATORY AGING. THE IOWA DURABILITY TEST IS A TWO-STAGE AGING PROCESS COMBINING STANDARD TFOT AND PRESSURE-OXIDATION TREATMENT (20 ATM IN OXYGEN AT 150 F) UP TO 1,000 HOURS. GOOD CORRELATIONS BETWEEN FIELD-SERVICE AGING IN IOWA AND LABORATORY AGING DURING THE IOWA DURABILITY TEST HAVE BEEN OBTAINED. THE MASTER TIME-EQUIVALENCY CURVE BETWEEN THE TEST IN HOURS AND THE PAVEMENT SERVICE LIFE IN MONTHS, ESTABLISHED BY COMBINING ALL ASPHALTS (VOID LEVELS) AND ALL PROPERTIES, INDICATES THAT 46 HOURS IN TEST WILL AGE ASPHALTS TO THE EQUIVALENT OF 60 MONTHS IN SERVICE. CORRELATION CURVES FOR DIFFERENT PROPERTIES AND DIFFERENT LEVELS OF PAVEMENT VOIDS WERE ALSO OBTAINED. A TENTATIVE SPECIFICATION FOR PAVING ASPHALTS, INCLUDING DURABILITY REQUIREMENTS BASED ON THE TEST, IS SUGGESTED IN LIEU OF CURRENT TFOT.