The conventional concrete repair procedure requires the removal of unsound and deteriorated concrete, steel cleaning, and coating with a bonding agent to form an integral connection with the new concrete. Concrete Repair Morgantown WV materials must have suitable dimensional stability and freeze-thaw durability to prevent drying and debonding.
It is recommended that a professional engineer be engaged to conduct inspections and design major structural repairs.
Concrete structures are designed to resist the compression forces of gravity, but they can also be subject to tension stresses. Whether the tension is from building loads or thermal contraction, the resulting stresses can cause cracks in concrete that will weaken its overall strength and durability. These cracks are best repaired early on so that they don’t lead to further deterioration and potential structural failure of the structure.
There are several different methods for repairing concrete cracks. The method chosen should be based on the evaluation of the crack’s causes and type. Suitable repair materials should be selected that achieve the desired performance in terms of durability and other important characteristics like cracking resistance, permeability, and freeze-thaw durability. It is also important to consider how the damaged area will be used. This will help to select the appropriate material, surface preparation, and curing regime for the repair.
Cracks in new concrete can occur for a number of reasons, including settlement shrinkage, construction movement, and drying shrinkage. Some of these movements can be controlled with stress-relieving joints and proper formwork placement. However, other factors, such as temperature fluctuations and chemical interactions, can affect the movement of concrete and cause it to crack.
Some cracks will self-heal and settle after a period of time. These are often referred to as “plastic shrinkage cracks” and will typically show up soon after the concrete has been poured. However, if the cracks are allowed to continue, they will eventually become shear or tension cracks that can compromise the structural integrity of the concrete and the reinforcing steel.
The most common method for repairing these types of cracks is routing and sealing. This is a relatively fast and simple process that involves using a router to cut a V-shaped groove along the length of the crack. Once the groove is cut, a sealant can be applied to prevent further damage. This method is best suited for dry cracks that are not actively leaking. It is not recommended for wet cracks that will require moisture-tolerant epoxy or other injection materials.
Delamination
Delamination in concrete occurs when a thin layer separates from the rest of the slab. It may be due to the corrosion of embedded reinforcing steel that expands and puts pressure on the concrete, or it can be caused by improper curing. Delamination can lead to a loss of surface finish and also impact the structural integrity of the concrete.
There are several different ways to repair delamination, but the best way depends on the severity and cause of the delamination. A thorough inspection should be conducted before determining the best method. This should include a review of design and construction documents, visual inspections, destructive and nondestructive testing, chemical and petrographic analysis of concrete samples, and a detailed maintenance history.
In many cases, delaminations are caused by a lack of proper reinforcement and/or a lack of good finishing techniques. To avoid this problem, the concrete should be properly resurfaced after it is poured. This can be done by grinding and polishing the concrete or by spraying a concrete overlay on top of the existing surface. Another way to prevent delamination is to ensure the concrete is compacted evenly and not left with voids or pockets. It is also important to avoid the use of de-icing salts, which can damage concrete and cause it to weaken or break down over time.
Before beginning a concrete repair, the contractor should thoroughly inspect the structure to determine the root cause of the delamination. If it is due to water corrosion of the reinforcing steel, the contractor should fully rehabilitate the concrete by saw-cutting the unsound concrete and removing it, cleaning and treating the exposed corroded steel, and replacing it with new structural steel. It is also essential to follow proper design and construction practices for the concrete, including using high-quality Portland cement, sizing the aggregate correctly, and achieving good surface finishes.
After the concrete is resurfaced, the contractor should sweep the area to remove any dirt or debris that can act as bond breakers. Sakrete Bonder and Fortifier should be applied to the surface of the repair and allowed to dry. Once dry, the contractor can then begin sanding the repair to match the texture of the existing concrete and use a feathering technique to blend the patch with the surrounding concrete. The final step is to skim coat the entire area with Sakrete Top ‘N Bond, which will help achieve a smooth and uniform appearance.
Loose Joints
Many warehouse and industrial floors have damage at the concrete floor joints. Unfilled control joints in particular are susceptible to chipping and spalling when hard-wheeled forklift traffic runs over them. This can lead to a lack of structural integrity for the slab and costly repairs and downtime. Our floor joint sealant, Epoxy Joint Filler, prevents damage by providing a resilient cushion for the load-bearing concrete slabs as well as preventing erosion of the control joint edges. Our epoxy joint filler is available in Regular Cure (RC), Fast Cure (FC), and Super Fast Cure (SFC) formulations.
The repair process depends on the type of joint and the severity of the damage. A full-depth repair is required when the damage extends beyond a third of the concrete thickness. When this is the case, a cementitious surface overlay is typically recommended.
Partial-depth repairs that abut working joints or cracks require the use of a compressible insert material such as Styrofoam or asphalt-impregnated fiberboard to reform the damaged joints or cracks and keep the new concrete from bearing on the existing concrete. The repair material should be designed to expand and contract with daily temperature fluctuations and have a thermal expansion coefficient similar to that of the existing concrete.
Alternatively, concrete repair can be accomplished using an epoxy that is mixed on site in small mobile drums or paddle mixers. The material is blended with a bond-enhancing additive for proper adhesion. The resulting mixture should be applied to the deteriorated concrete and lightly troweled with a feathered edge to match the original concrete finish. The resulting epoxy repair should be cured properly to achieve maximum strength and performance.
For full-depth repairs that involve removing concrete from the damaged area, a wire brush and/or shot blasting are usually required to remove all corrosion and dirt, as well as any loose and weak areas of the concrete. The rebar should be cleaned to eliminate any exposed rust or other signs of deterioration and then covered with a protective coating.
Expansion joints in concrete help the concrete flex and absorb predicted movement caused by changes in the ground conditions, such as soil settlement or changes in ambient temperatures. Failing to properly install and maintain these expansion joints will result in their failure and a wide range of undesirable consequences.
Structural Damage
Structural concrete damage can occur in many forms, including sagging floors, walls, and foundations. Left unaddressed, structural damage can lead to serious building problems, affecting everything from plumbing and electrical systems to water damage and even the complete collapse of the structure. Structural concrete repair techniques focus on protecting load-bearing structures from further deterioration while restoring their original design capacity.
Portland cement mortar and grout are the most commonly used concrete repair materials. Their low cost and ease of use make them an attractive choice for repairing structural concrete. However, the performance of Portland cement is highly dependent on the quality of the base concrete in which it is placed. This means that it is critical to prepare the surface of the damaged concrete to ensure the best possible bond with the repaired materials.
Surface preparation methods and concrete removal techniques can have a significant impact on the life of the repaired concrete. For example, chipping hammers that are not matched to the job can cause damage to the concrete during removal. To extend the life of the repairs, it is recommended to use a lightweight 15-pound electric or pneumatic chipping hammer that will remove the deteriorated concrete without damaging the sound concrete underneath.
Another issue that can have a major impact on the durability of the concrete repair is the type of material selected to fill the damaged areas. For example, a concrete mix with a high slump can be difficult to work with and may require extensive hand finishing. In contrast, a concrete mix with a low slump can be easily worked and has a faster set time. It is recommended to select a concrete repair material with the desired slump for the installation method.
Once the concrete repair is completed, it’s important to consider how the structure will be utilized. If the structure will be load-bearing, it is advisable to install a reinforcement bar tie system that will increase the tensile strength of the structure. Otherwise, it is advisable to cover the entire surface with a waterproofing membrane to protect the repair and prevent further deterioration.
