Abstract:
Field and laboratory studies were conducted to determine the feasibility of detecting and quantifying segregation in hot-mix asphalt pavements. The study involved extensive testing at 19 field sites in Michigan. Areas of apparent segregation were classified as light, medium, and heavy. At the selected sampling areas, 1-min nuclear density measurements were made, cores were taken and incinerated, asphalt contents and air voids were determined, and gradation tests were performed. Statistical comparisons were made by using t-tests to characterize the differences between the measured nuclear density and percent passing various sieves. More than 80% of the nuclear density measurements supported the visual observations of a heavy degree of segregation when the significance of the differences (the p-value) between the areas compared was less than 0.001. Moreover, for areas with medium or heavy segregation, the probability that significant differences in nuclear density between segregated and nonsegregated areas with p-values less than 0.001 corresponded to significant differences (p-values less than 0.01) in aggregate gradation was .88. On the basis of the results, a spreadsheet, mbitseg2, was developed to perform statistical tests with the nuclear density measurements obtained during the paving operation. After 6 months of trial testing, the program has been accepted and implemented by the Michigan Department of Transportation, the Michigan Asphalt Paving Association, and the asphalt industry. The program is available on a web page (http://www.egr.msu.edu/prce) in Excel (mbitseg2.xls) and QuattroPro (mbitseg2.wb3) formats.
