Joint Saw Cutting and Matching

Joint saw cutting is an important construction step for thin concrete overlays. As an example, in monitoring the construction of a thin overlay along TH-53 near Duluth, MN, MnDOT observed delayed joint saw cutting because the sawing crew was unprepared for the speed of thin overlay placement, which is naturally faster than that of conventional overlays (Watson and Burnham 2009).

In addition, and as described previously, the matching of transverse and longitudinal joints in the overlay to those in the underlying concrete pavement is critical for bonded overlays, and requires careful workmanship in locating those joints and sawing them to the prescribed depth. Furthermore, saw cutting in unbonded overlays of existing asphalt pavements may need to account for rutted asphalt to maintain the specified saw cut depth. That is, it may be necessary to cut deeper to ensure the formation of the weakened plane joint. Recommended minimum saw depths depend on the overlay and joint type, as presented below (Harrington and Fick 2014):

• Bonded concrete on concrete:
  
  • Transverse: Full thickness of bonded overlay plus 0.5 inch (13 mm).
  • Longitudinal: Minimum 1/2 of the overlay
• Bonded concrete on asphalt or composite and all unbonded overlays:
  
  • Transverse: 1/4 to 1/3 of the overlay
  • Longitudinal: 1/4 to 1/3 of the overlay thickness.