Impact of Joint Sawing Timing and Depth on Random Cracking: A Case Study

Abstract

The joint sawing “window” has long been recognized as critical to provide a saw cut that is (1) not too early and damages the surrounding concrete, and (2) not too late and results in random slab cracking. The depth of sawcut has also been recognized as critical to providing an adequate weakened plane that sufficiently minimizes the potential of random cracking but provides as much aggregate interlock as possible for load transfer. Both of these aspects of joint formation must be done properly or serious problems such as random cracking can develop. This JPCP project was constructed in a wet-freeze climate in North America that developed significant early longitudinal cracking. Data collected from the project led to an analysis that demonstrates how both time until saw cutting and depth of the saw cut correlated strongly with the amount of random longitudinal cracking that occurred within a few months after placement. Results showed that had the joints been formed within the specification limits for depth and timing there would have almost no chance of random longitudinal cracking.