Ahn, Hyung Jun

Practitioners have often wondered whether; during ride measurement with inertial devices; the motion of the laser through pavement texture introduces non representative values of international roughness index (IRI); particularly in certain textures. In response to this problem; a special texture study created a non-textured strip by a recession of the middle 4 ft of a texturing broom dragged longitudinally behind the paver. The study measured IRI and other surface properties in adjacent textured and non-textured strips by using a lightweight profiler outfitted with a line laser and a triple laser arranged in tandem. IRI measurements were performed after sufficient concrete strength gain and repeated as soon as the joints were sawn. The same measurements were repeated after the joints were deployed. Results showed a significant difference between the IRI of a textured strip and that of a non-textured strip. Further analysis indicated that; although texture appears to affect IRI; this effect was amplified by the type of laser used; as the triple laser appeared to indicate higher IRIs in comparison with the RoLine laser. Although the RoLine is not a reference profiler for IRI values unaffected by texture; the prevalence of the RoLine and the triple laser in construction acceptance testing is sufficient reason to be concerned about the difference inherent in the obtained results. Chi-square and t-test statistical analysis showed that laser type induced comparable and even higher IRI anomalies than did the experimental drag texture. In addition; the texture-induced IRI anomaly can be minimized by measuring smoothness for acceptance at least 2 weeks after paving. There was no significant difference in pavement noise in terms of on board sound intensity (OBSI) between textured and non-textured strips. The friction numbers derived from the Dynamic Friction Tester indicated a correlation between the nontextured and textured strip friction numbers in each of the 6 sections. This indicated that the finishing process before texturing continued to influence the microtexture even after the broom drag. This finding is limited to the texture types investigated. Therefore; extrapolation of these results to other textures should be done with caution due to anomalous laser -induced IRI on certain textures.

This report presents the findings from an eight-year performance evaluation of eight cells (Cells 16-23) built at the Minnesota Road Research Facility (MnROAD) in 2008. The constructed cells were used for two performance evaluation studies of: 1) unbound base materials (i.e.; recycled asphalt pavement (RAP); recycled concrete aggregate (RCA); and taconite) and Class 5 aggregate as the road base material and 2) surface materials that include warm mix additives (WMAs); RAP; and different binders with different performance grades. The eight cells were tested via a surface distress survey; rutting tests; falling weight deflectometer tests; international roughness index (IRI) tests; and friction tests. Disk-shaped compact tension (DCT) tests also were performed using the mixture samples; and the performance of the unbound base materials (Cells 16-19) was evaluated using light-weight deflectometer (LWD); dynamic cone penetrometer (DCP); and gradation tests. After eight years of service (approximately 5.6 million equivalent single-axle loads); the cells remained in good condition in terms of their resistance to surface distresses; rutting; stiffness; IRI values; and friction. Consequently; it was difficult to compare the performance of the various unbound materials and mixtures. The unbound recycled materials and taconite performed as well as the Class 5 aggregate base material in terms of the gradation; DCP; and LWD test results. All mixture types; regardless of RAP content; binder grade; or the presence of WMA; exhibited similar performance.