Material Charaterization and Performance Properties of Superpave Mixtures

Abstract

The primary objectives of this research study was to characterize properties of two NCDOT Superpave mixes with regards to fatigue distress, and to develop phenomenological fatigue relationships for these mixes based on various levels of strain, asphalt content, air void content, and temperatures. Of particular importance was the sensitivity of the Superpave mixes to asphalt content and air void content that are usually expected in-situ.

Fatigue characterization of typical pavement sections using NCDOT fatigue models and using mechanistic analysis procedure suggests that the pavement fatigue life is sensitive to the mix variables and test temperatures considered in this study. A decrease in asphalt content by 0.5-percent (by wt. of mix) results in decrease of 18 to 25-percent fatigue life. An increase in 2% air void content will reduce pavement life by about 40% for 12.5-mm mixes, and by almost 60% for 19-mm mixes. An increase in temperature was found to result in decrease in fatigue life of pavement section under consideration, although, fatigue testing was conducted in controlled-strain mode-of-loading. A 5°C increase in temperature results in about 25-percent reduction in pavement life. Based on the overall result of the analysis, it appears that 19-mm mix is more sensitive to mix and test variables as compared to the 12.5-mm mix.

The study of frequency effect on fatigue life of typical pavement section suggests that prediction of fatigue life of pavement section is independent of load frequency used in fatigue test as long as tensile strain is computed based on the same load frequency.