When properly constructed over properly prepared pavements, bonded concrete overlays are one of the longest lasting treatments. Concrete overlays also increase structural capacity, even if that is not the primary objective of the maintenance activity. On concrete pavements, BCOs eliminate extensive scaling or surface cracking and improve friction, noise, and rideability. Why (advantages): On asphalt pavements, bonded concrete overlays eliminate surface distresses such as rutting and shoving. On concrete pavements, random cracks should be repaired, slabs should be stabilized where there is faulting and/or pumping, asphalt patches should be replaced with concrete patches to ensure bonding, joint spalling should have partial depth repair, and scaling should be removed and cleaned. Asphalt pavements to be overlaid should be at least 3-4” thick. Milling the asphalt surface also helps improve the bond between the concrete overlay and asphalt interface. Rutting greater than 2” on asphalt pavements should be milled to correct the profile. The existing pavement (concrete or asphalt) must be in good condition with no significant stresses. Whitetopping overlays have been successfully used on interstate highways, state primary and secondary roads, and intersections, as well as major airport and general aviation runways, taxiways, and aprons. Where: BCOs are appropriate for busy intersections and asphalt roads rutted by heavy truck and bus traffic can be rejuvenated with a rigid surface that won’t rut or shove. Bonded together, the overlay and the existing pavement perform as one monolithic pavement, with the existing pavement continuing to carry a significant portion of the load. Bonded concrete overlays are constructed using conventional concrete paving practices and procedures. Over asphalt pavements, transverse joints are saw cut, typically at 2 to 6 ft intervals. The overlay is placed, and saw cuts are placed in the overlay over underlying joints, patches, and working cracks in order to accommodate movements and prevent reflective cracking. This may be done by shotblasting, sandblasting or cold milling. A critical step is roughening the substrate surface so that the new concrete will firmly bond to the old surface. The pavement is first analyzed, and then prepared with any necessary repairs. What: 2 to 5” of bonded Portland Cement Concrete is placed over asphalt, composite or existing concrete pavements that are in good to fair structural condition for long lasting and cost effective resurfacing and minor rehabilitation. To receive email updates about this project, visit MnDOT’s Office of Research & Innovation to subscribe.(BCO, formerly known as whitetopping and bonded overlays)
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