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71 evaluated included VMA, initial construction density, and related to durability are less likely to occur in this short time densification (change in field density) after 10 million ESALs. period. The uncompacted void content of the fine aggregate had a significant relationship with the as-constructed density. LA abrasion was the first variable entered for change in density, 4.5 SUMMARY OF DATA FROM IN-SERVICE PAVEMENTS AND ACCELERATED LOAD and uncompacted voids content of fine aggregate was the FACILITIES fourth variable entered. The relationships for both variables were significant. Numerous Superpave sections have now been in-service In order to further analyze the data, the data set was for 10 years or longer; however, the data from these sections, divided by binder grade with all of the PG 67-22 sections particularly aggregate properties, are not readily accessible. grouped together and all of the PG 76-22 sections grouped The best potential source of data, the LTPP Program, only together. It was felt that the modified binders may be mask- stores limited Superpave aggregate consensus property data. ing the effect of the aggregate properties. There were only Attempts to use this data were hindered by a lack of traffic nine Superpave sections placed with PG 67-22. Therefore, a data. The most significant accelerated testing related to aggre- stepwise regression could not be performed with the previ- gate properties has been conducted at the Indiana DOT/Purdue ous group of predictor variables. Instead, individual regres- University APT Facility. This work was discussed in Chap- sions were performed with aggregate properties such as fine ter 2. Three test tracks have been operated since the imple- aggregate uncompacted voids, coarse aggregate uncompacted mentation of the Superpave method: MnRoad, WesTrack and voids, and F&E at the 31 ratio, which might be expected to be the NCAT Test Track. Aggregate properties were not an correlated with rutting. None of the aggregate properties pro- experimental variable at MnRoad or WesTrack with the excep- duced significant relationships. For the 19 sections with PG 76- tion of the coarse aggregate angularity of the replacement 22 binder, an ANOVA performed as part of the regression sections at WesTrack. Coarse aggregate angularity data from analysis indicated a poor but significant relationship for the fine WesTrack was in general agreement with the relationship aggregate uncompacted void content (p = 0.011, R2 = 0.31). developed by Cross and Brown (17). There were a number It should be noted that all of the sections in the 2000 of different aggregate types and gradations placed at the 2000 NCAT Test Track performed well in rutting. It is difficult to NCAT Test Track. All of the sections performed well. Strong develop relationships between a response variable, such as correlations were not evident among rutting, VMA, construc- rut depth, and aggregate properties when all of the rut depths tion density or densification under traffic, and aggregate prop- are small, even though traffic, climate, and pavement struc- erties. A weak relationship was obtained between rut depth ture were constant for all of the sections. The application of and fine aggregate uncompacted voids for the sections con- 10 million ESALs occurred in a 2-year period. Distresses structed using PG 76-22 binder.