Concrete Crack & Joint Sealing

Concrete Crack & Joint Sealing

“All cracks and joints must be kept sealed.”

Relatively large volume changes are produced in portland cement concrete (pcc) by variations in temperature. Because of this all such pavements crack; it is natural property of the material. To make the concrete crack straight,  pcc pavements have joints at frequent intervals.

Joints are either formed the full depth of the slab or grooved to a depth of one-sixth to one-quarter of its thickness. Full-depth joints are junctions between slabs to permit expansion, to control cracking, or to meet construction requirements. Grooved joints are formed or cut to force cracking along the weakened plane. Depending upon their function, they are called expansion joints, contraction joints, or construction joints. They may run in transverse, longitudinal, or construction joints.

All cracks and joints must be sealed with some adhesive material to prevent damage to the pavement from water and foreign matter. Asphalt, with or without an additive such as rubber, has been widely used as a crack and joint sealing material.

The methods used for sealing cracks and joints are essentially the same. Both consist of cleaning out the upper portion of the crevices and filling them with a sealing material. To be effective, the sealing material must stick to the sides of the opening. For this reason any material which will prevent a good bond must be cleaned out. If sand, gravel, dust, or other foreign matters have accumulated in opening they must be removed. They may cause the edges to spall when the crack or joint closes under expansion of the slab in hot weather. Old sealing material, which has become hardened, should also be removed.

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