Technical Questions

ACI Committees, Membership, and Staff have answered common questions on a variety of concrete related topics.



When should saw cuts be made on a concrete slab?

Q. When should saw cuts be made on a concrete slab, and what precautions should be taken to prevent damage?

 

A. Saw cuts, also called relief cuts, should be timed carefully to control cracking and maintain the integrity of the slab. According to ACI 302.1R-15, saw-cutting should occur before random drying-shrinkage cracks form and when the surface is firm enough not to be damaged by the blade. Timing is critical, and cuts should typically be made within 4 to 12 hours after placing the slab, depending on the temperature and weather conditions.

For early saw-cutting, ACI 325.12R-02(19) suggests a range of 2 to 6 hours after placing the concrete, with hotter conditions requiring cuts even sooner. In hot weather, saw cuts may need to be placed within 1 hour, while in cold weather, they can typically be delayed to about 4 hours (ACI 224.4R-13). The goal is to make the cuts as soon as possible without causing excessive raveling, yet early enough to prevent random cracking (ACI 325.9R-15).

The depth of the saw cuts is also important. Conventional saw cuts should generally be made to one-fourth the depth of the slab (ACI 327R-14), although early-entry saws can cut to a lesser depth and still be effective (ACI 224.4R-13).

In terms of preventing damage where cuts cross each other, joint protectors can help maintain the integrity of the slab at intersections. These protectors minimize chipping and damage at the cut junctions, which seems to have been an issue in your case.

For best results, environmental factors such as temperature, wind, and sunlight should be managed. On hot, dry, or windy days, initial cracking can occur rapidly, so techniques like fogging, using monomolecular films, or nighttime placements can help control these conditions (ACI 302.1R-15).

By adhering to these guidelines, saw cuts can be optimized to prevent cracking and damage, ensuring the long-term durability of the slab.

 

References: ACI 302.1R-15; ACI 325.12R-02(19); ACI 224.4R-13; ACI 305R-20; ACI 327R-14; ACI 325.9R-15

Topics in Concrete: Cracking; Slabs; Concrete Joints; Hot Weather Concrete

Other Sources for Answers

Search other resources on the ACI website for answers to technical questions