The design, construction, performance and rehabilitation of ten whitetopping (concrete overlay of asphalt) test cells at the Minnesota Road Research Project (MnROAD) are described and discussed. These test cells can be considered to constitute an accelerated loading test because the concrete thicknesses represent low-volume road applications, but they are subjected to Interstate traffic (with high volumes of heavy truck traffic). In manyof the lower volume road applications for which these designs would typically be employed, it would take more than 50 years to accumulate the same number of heavy vehicle loads actually carried by the MnROAD whitetopping cells, many of which are still in serviceable condition. The performance of the original whitetopping test cells at the MnROAD project appears to berelated to traffic volume, wheel load placement and layer bonding, particularly for the 3-in and 4-in [75-mm and 100-mm] test sections. Observed good performance can be attributed to good support by (and bond with) the underlying asphalt layers. Poor performance was observed where longitudinaljoints were placed in or near the wheel paths. The rate of reflective cracking is also affected by traffic levels, with more rapid development in the driving lanes than in the passing lanes. The incidence of reflection cracking appears to depend on the relative stiffnesses of the concrete and asphalt layers (taking environmental effects on asphalt stiffness into consideration). Recommended best practices for whitetopping repair were developed at MnROAD. These practices focus on achieving good bond, avoiding reflective cracks and providing good curing.
Abstract