Concrete repair is a process of correcting damage to concrete structural elements. Concrete Contractors Dallas TX involves the evaluation of the extent of damage and its impact on the safety and serviceability of a structure. The right choice of repair materials is essential for successful repairs. They should have low shrinkage, which is important to prevent debonding with the existing concrete. They should also be moisture tolerant, as water can cause cracking.
Concrete repair is usually done because of structural damage that needs to be addressed. The cause of the damage must be inspected before any repairs are carried out as this will ensure that the correct procedures are used and therefore provide a long-lasting solution.
Steel reinforcement corrosion is the most common problem encountered when repairing concrete structures. It is also the most frequent reason for cracks to appear in repaired concrete. Corrosion problems can be caused by exposure to chlorides, sodium chloride (road salts), hydrochloric acid and other chemicals. They can also be caused by excessive water content in the concrete or a low freezing temperature. Corrosion can also lead to spalling, where the surface concrete flakes away from the main structure, and pitting of the concrete surface.
Other causes of concrete damage include abrasion, impact loading, freeze/thaw cycling and chemical attack. Repairing these types of damages is more challenging because of the need to restore the original material properties and performance. Several repair methods are available for concrete damage: dry packing, grinding, jacking and mortar replacement. Some of these methods may be suitable for certain conditions like leveling irregular slab surfaces, but they should be carefully selected to assure expected durability of the repaired concrete.
It is also important to choose the appropriate repair materials. The selection process should consider a number of factors, such as the performance characteristics required for the damaged structure, compatibility with existing concrete, cost and ease of application. For example, some repair materials need a special curing regime to achieve the desired durability. During curing, the materials must be protected from water exposure to avoid debonding.
It is generally considered that the average durability of repaired concrete structures is less than 25 years. This is mainly due to the fact that the majority of concrete repair works do not follow best practice procedures and are influenced by a range of other factors.
Preparing the Surface
The success of concrete repairs relies primarily on the mechanical bond of a properly prepared substrate with the repair materials. This bond is developed by properly cleaning and preparing the existing concrete surface for application of the new material. The good news is that it’s fairly easy to get a high bond strength with the right approach.
The bad news is that most contractors ignore or skip this first step in the process. This is unfortunate because if the work is done properly, the resulting repairs are usually long lasting.
Preparation is important whether you are repairing cracks, surface scaling, spalling or other problems in the concrete or resurfacing the concrete with coatings, overlays, stains or other decorative products. In fact, the preparation process may be more critical for these applications than it is when re-concreting or adding strength to a structural member.
Concrete surfaces should be clean and free of oil, grease, rust stains, mildew or other foreign matter that will prevent topical materials from adhering to or penetrating the host concrete. Chemical cleaning can be effective, but it is important to follow the manufacturer’s recommendations and test the surface for suitability for the application. Acid etching is another common method of surface preparation for concrete, but it must be carefully managed to ensure the correct level of roughness required for certain coatings and resurfacing applications.
If the concrete is deteriorating due to corrosion of steel reinforcement, it’s also critical to remove the corrosion products from the surface before proceeding with the repair. This could require abrasive blasting, wire brushing or chemical cleaners. It is important to ensure that the corroded areas are completely cleaned down to the reinforcing steel so the new concrete will not be susceptible to corrosion failures in the future.
Once the concrete has been cleaned, it should be allowed to dry completely. Ideally, the concrete should be cured for at least two weeks before beginning the repairs. During this time the concrete should be checked for movement, vibration, shrinkage and expansion. It is also important to check the concrete for proper moisture content, especially if the repair will be exposed to freezing temperatures.
Applying the Repair Material
When a repair contractor decides on which concrete product to use, he or she should consider the environment and the type of load that will be placed on the repaired area. For example, a repair material needs to be freeze-thaw resistant and its tensile strength and abrasion resistance should match the original concrete. Also, it is important that the permeability of the material be comparable to the original concrete. This is important for the proper drainage of a repair area and to avoid excessive moisture problems.
Another factor to consider is the location of the damaged area. For example, in a driveway, a repair material needs to have good skid and abrasion resistance to prevent damage to the cars. In addition, a repair material should be strong enough to withstand the load of vehicular traffic.
Finally, the temperature of the repair site will impact the choice of a repair material. For example, some products are not suitable for hot weather because they can experience high shrinkage and stress due to thermal expansion. Lastly, a proper curing regime should be considered. Some materials need extensive water curing while others require little or no water to achieve their desired strength.
Before applying a concrete repair material, the surface should be roughed with a mason’s stone or grinder and cleaned of any oil or dirt that could inhibit bonding with the concrete. If a contractor has any doubts about which preparation method to use, he or she should contact the manufacturer of the concrete repair product for expert insight.
During the application process, contractors should be careful to fill in all of the cracks and holes. It is important to note that the repair mix should not exceed the maximum slump or slump test for the specific type of mix. Using too much repair material can create an unstable structure and result in the failure of the repairs.
The most effective repairs will last a long time and are designed to resist the natural stresses of the structure. The most durable repairs will be those that have a low shrinkage rate and are designed to withstand shear or bending forces in tension zones.
Finishing the Job
The process of repairing concrete surfaces can be time consuming and complicated, especially when the damage is severe. Whether the repair is for a driveway, patio, pool deck or indoor floor, there are many steps involved. There’s surface preparation, mixing water into the cement, applying the concrete patch, waiting for it to dry, and, in some cases, adding paint.
There are also specialized concrete repair products that make the job much easier. For example, the contractor-grade product Eurepoxy is a thermoplastic rubber that you pack into cracks in concrete after etching it for best adhesion. When the cracks are filled, it creates a permanent and durable seal that’s self-leveling, so it can give slightly with temperature-caused expansion and contraction of concrete. It’s also resistant to abrasion and chemicals and can be used on concrete, asphalt and vinyl surfaces.
Using a pre-mixed repair compound like Red Devil cuts application and curing time down to minutes. This is especially helpful for large areas that need to be repaired quickly. For small repairs of cracks, a chisel and hammer may be enough to get the job done. For larger areas, a power trowel and a concrete mixer may be needed for mixing the concrete and spreading it into the cracks.
Aside from the equipment listed above, other basic tools include brooms, hand tools and hand or power screeds. Other job specific equipment could include a power vibrator and saw cutters for concrete. During the course of the work, contractors will need to follow established safety practices. They will note the ground temperature, air temperatures and humidity levels to ensure the mix is designed to set in proper time.
The ability to read and understand plans, blueprints, sketches and specifications is also important for a concrete finisher. Depending on the size of the project, they may also need to be able to operate a conveyor, pump or power buggies. These vehicles are used to transport concrete and help with the smoothing and finishing of the concrete surfaces for projects such as sidewalks, curbs, culverts and catch basins.
