WATER SENSITIVITY TEST METHODS FOR ASPHALT CONCRETE MIXTURES: A LABORATORY COMPARISON

This study provides a comparison of four asphalt concrete water sensitivity (stripping) test methods by ranking the relative resistance to water-induced damage of a variety of field-prepared mixtures obtained during construction. Each test method evaluates water sensitivity by determining resilient modulus or indirect tensile strength, or both, of a compacted specimen before and after moisture conditioning. Conditioning of the samples is performed by vacuum saturation to predetermined levels and, in some cases, freeze-thaw cycles. One test method consists of vacuum saturation only. Another adds a single freeze-thaw cycle to vacuum saturation. The third method is a repeat of the second method, but at a lower saturation level. Finally, the fourth test method is an extension of the third, involving additional freeze-thaw cycles. Test results indicated that stripping damage did not occur in specimens subjected to vacuum saturation only. Freeze-thaw cycles caused damage to the specimens. Higher saturation levels resulted in increased damage to the specimens, as expected, but the rank of relative water sensitivity of the mixtures was found to be nearly the same. Laboratory performance after seven freeze=thaw cycles varied with aggregate and asphalt characteristics and could not be predicted using performance data from one freeze-thaw cycle only.