Repairing Control Joints: Understanding the Importance of Proper Sealing and Filling
Control joints are planned cracks that enable movements caused by temperature changes and drying shrinkage. Thus, if the concrete cracks and shrinks, the control joint must be placed so the slab will crack on a line rather than randomly across the slabs. The slab will continue to shrink and widen the joint for years. The control joint can be left as is, sealed, or filled. Filing or sealing must be put off as long as possible to let the joint widen.
Importance of Sealing or Filling Control Joints
Sealing is performed with a flexible material often installed over the backer rod to offer the seal the proper shape in the joint. Meanwhile, filling is carried out the full length of the joint using a material that has enough compressive strength to support the joint’s edges from stresses that heavy, hard-wheeled traffic may impose. Without proper sealing or filling, the control joints can become areas for dust, dirt, and debris to collect and cause issues.
Moreover, unsealed or unfilled control joints in food processing, medical, and pharmaceutical facilities can lead to more serious issues. They can harbor water, harmful bacteria, and moisture. Also, without proper sealing and filling, moisture may migrate through the joints into the base and subbase and debris filling the joint, affecting adjacent slab sections. Consequent base/subbase and slab distress can lead to rocking slabs and vertical displacement at the joint.
Repairing Control Joints
To repair a control joint, there are different techniques that can be used including epoxy injection. Your choice of technique depends on how wide, long, or deep the crack is. The majority of concrete crakes are associated with shrinkage, wrong joint placements, heat, over stress, movements, and loading conditions. Repairs can be completed using epoxy injections applied directly to the cracks. When injecting epoxy, begin with a low-pressure injection setting and increase the pressured as needed.
Control Joint Filler Options
Epoxy control joint fillers incorporate the proper 80-85 durometer hardness and the flexibility to help prevent welding the slabs together, which can lead to the slab’s delamination. When mixed properly, semi-rigid epoxy joint fillers offer a smooth, flowable easy-to-pour consistency, and convenience. These fillers are often available in a one-to-one ratio and easy-to-use options that can be applied manually using a bulk gun or pumped with a dual component pump.
Furthermore, polyurea control joint fillers also provide the desired 80-85 durometer and can help prevent slab welding. They have a higher elongation, which helps in resisting tearing because of shrinkage and slab movement.