Date: September 18, 2017
Ten Tips for Controlling Cracks
There are three truths in life… death, taxes, and concrete will absolutely crack. Joints are there to make sure we have control of where those cracks happen.
Follow these simple steps to see what other preventative measures you can take to control cracks in concrete:
- Make control joints at least 1/5 to ¼ the thickness of the slab.
- Don’t space joints (in feet) farther apart than 2 to 3 times the slab thickness (in inches.)
- Locate joints at changes in slab thickness and plan dimensions.
- Plan the joint layout so there are no re-entrant corners.
- Don’t place concrete directly against walls, columns, slab inserts, or an older concrete slab. Separate the slab from obstructions with an isolation joint.
- Compact the subgrade thoroughly to avoid settlement cracks.
- Trim the subgrade to ensure a uniform slab thickness; if necessary, remove high subgrade areas and recompact.
- Don’t add more water than is needed to produce workable concrete. Excess water causes more concrete shrinkage and increases the risk of shrinkage cracking.
- Cure the concrete so it continues to gain strength and delays drying shrinkage until the concrete is strong enough to resist shrinkage cracking.
- Don’t walk the reinforcement to the bottom of the slab. Place the reinforcement 2 inches below the top surface.