Do You Need to Install Concrete Control Joints? Do You Need to Install Concrete Control Joints?

Although concrete control joints are not needed in all applications of concrete, they are almost without exception needed in applications where larger concrete slabs are poured. Without these control joints, concrete slabs will inevitably develop uncontrolled cracks in the concrete due to expansion and contraction.

Controlling Concrete Cracks

Concrete expansion and contraction and the resulting concrete cracks are typically caused by temperature and moisture changes in dry concrete. The key to maintaining good solid concrete slabs is to control this cracking in the slab. Although a builder cannot always keep concrete slabs from cracking, they can control where it cracks, just by installing joints in the slab. With proper joints placement, concrete that cracks because of contracting or expansion will nearly always crack in a control joint.

Control Factors

Shrinkage and drying factors that can cause concrete slab cracks can be controlled by factors that include:

  • Using cement that has a low water-cement ratio
  • Use a higher ration of coarse aggregate, compared with finer size aggregate
  • Use of agents that reduce water and its related drying shrinkage
  • Choice of surface with low slump on which concrete is poured
  • Control of fresh concrete curing time to minimize shrinkage

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