Routing and sealing of cracks in concrete is a method commonly used for dormant cracks that do not require restoration of tensile strength. The process involves enlarging the crack along its exposed face to form a V-shaped groove, with a minimum width of 6 mm and a depth of 6 to 25 mm. This groove is then filled and sealed with suitable material. For quicker work, the routing operation can be omitted, but it may result in lower performance of the repair. However, it’s important to note that the surface of the repair material may be higher than that of the adjacent concrete, which could affect the aesthetic appearance.
On roadway pavements, pouring hot tar into the cracks is a simple and inexpensive method of crack sealing. When using hot-poured joint sealants, it’s crucial to ensure that they bond with the concrete and do not melt or flow under operating conditions. The grade of the sealant must also be suitable to withstand moving traffic without any damage.
The groove over the crack can be made using hand-held tools, concrete saws, or pneumatic tools. Afterward, the groove is cleaned by air blasting, sandblasting, or water-jetting to remove grease, oil, or dirt. It’s important to thoroughly clean the surface with water and ensure it’s dried before applying the sealant. Proper preparation and application of the sealant are essential for an effective repair.
The procedure is most effective on flat horizontal surfaces, but can also be used on vertical and curved surfaces with the use of a non-sag sealant. It is commonly used to waterproof concrete surfaces where water accumulates. The sealants used can be made of various materials, such as epoxies, urethanes, silicones, polysulfides, asphaltic materials, or polymer mortars, as long as they can withstand cyclic expansion and contraction without becoming brittle over time. Cement grouts are avoided due to their tendency to crack in the future.
To apply the sealant, a dry groove is created and the sealant is placed into it, then allowed to cure. If it is desired that the sealant be able to move freely without resistance at the bottom of the groove, a bond breaker in the form of polyethylene strip, waxed paper, or foil may be used. The groove is typically made rectangular, and care is taken to avoid debonding the sealant from the side surfaces. In some cases, strip coating or over-banding with urethane may be applied over the repaired surface to reduce the chances of edge spalling and make the treatment more uniform. This coating is typically 25 to 75 mm wide on each side of the crack and 1 to 2 mm thick.
When used on a larger scale, this process is sometimes referred to as blanketing. Elastic sealants, which return to their original shape when external stresses are removed, are used for this method. The groove formed at the top of the crack to receive the sealant is called the “chase.” A bond breaker is required at the bottom of the chase for elastic sealants. The width and depth of the chase are determined based on the expected movement of the joint, with a safety factor of 5 to account for aging and fatigue. The tensile stress in the sealant material should not exceed the cohesive capacity of the material, and typically ranges from 135 to 345 kPa. The width of the chase is typically kept at least six times the expected movement of the joint to accommodate for compression. The minimum depth of the chase is usually 20 to 25 mm, and a rectangular shape is commonly used for elastic sealants. If any reinforcement is exposed during the cutting of the chase, the depth is increased so that the sealant can go behind the reinforcement bars. The bars should be cleaned and coated with bitumen before placing the elastic sealant. The quality of the sealant can be checked in the field by pulling a layer of the sealant, with failure ideally occurring through the sealant itself or by stripping away a skin of mortar, but no separation should occur between the mortar and the sealant.