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Cracks in Curb and Gutter

Hotline Question

At a chemical plant we poured 100 feet of concrete curb and gutter and sawed joints at a 25-foot spacing. Plans called for rectangular 2x8-inch weepholes in the curb spaced at 12 1/2 feet.

About a third of the curb and gutter is fine but in the other 65 feet there are four random cracks. Instead of cracking at the joint, the concrete cracked at the weephole. What caused the cracks and whats the best way to repair them?

Troubleshooting Answer

The cracks are probably caused by a stress-raiser effect at the weephole opening. Any time you create a reentrant or inside corner, concrete is likely to crack at that location even if there are joints nearby. Ive seen cracks of this kind form within a couple of inches of a sawed joint. The rectangular hole in the concrete created a stress concentration or a notch effect at the corner of the rectangle.

Dont try to glue the cracks back together. The concrete may then crack in a nearby location-perhaps at the other inside corner of the weephole. If the crack must be sealed to prevent liquids from flowing through it, rout out the surface and fill it with an elastomeric sealant of the kind used for sealing highway joints. A silicone or polyurethane product would work for this purpose.