When formed with a groover, the groover bit should cut to what fraction of the slab thickness?

When formed with a groover, the groover bit should cut to what fraction of the slab thickness?

• A. 1/8
• B. 1/4
• C. 1/3
• D. 1/2

Answer: (B)

Creating a contraction joint with a groover establishes a deliberate weak plane where cracking will occur as the concrete shrinks. The groove should cut to about one-quarter of the slab thickness. This depth provides a reliable joint that guides cracking without overly compromising strength. If the groove is cut deeper, the slab is weakened and edge damage or telegraphing can happen. If it’s too shallow, the crack may not follow the groove and could appear elsewhere. So, cutting to one-quarter of the slab thickness is the standard depth for groover cuts.

Creating a contraction joint with a groover establishes a deliberate weak plane where cracking will occur as the concrete shrinks. The groove should cut to about one-quarter of the slab thickness. This depth provides a reliable joint that guides cracking without overly compromising strength. If the groove is cut deeper, the slab is weakened and edge damage or telegraphing can happen. If it’s too shallow, the crack may not follow the groove and could appear elsewhere. So, cutting to one-quarter of the slab thickness is the standard depth for groover cuts.