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What You Need to Know About Concrete Repair

Concrete Repair Colorado Springs is a necessary part of maintaining your concrete. It prevents bigger issues down the road, like cracks that become trip hazards for small children and elderly residents.

Getting good results from your repairs is dependent on several factors. Among these are the physical properties of the repair material, including drying shrinkage, modulus of elasticity, permeability, and freeze-thaw durability.

  1. Identification

Concrete repair is necessary for various reasons, from aesthetics to safety concerns. Whether it is a crack in a sidewalk that’s creating a tripping hazard or a spalling floor joint in an industrial plant, it’s important to find a contractor who can provide the right solution for your specific situation. They will have the knowledge and equipment to make the repairs quickly, accurately, and safely. A reputable contractor will also offer warranties and insurance to protect your investment.

A thorough condition evaluation is the first step in any concrete repair process. This should include a structural analysis of the structure, destructive and nondestructive testing, visual inspection, records of maintenance, and chemical and petrographic testing of concrete samples. This will help determine the cause of deterioration or distress, which in turn will allow for the selection of appropriate repair methods and materials.

Minor defects in concrete are cosmetic and can often be repaired by simply filling the cracked areas with dry cement. The existing concrete must be thoroughly cleaned of unsecured stone, and the cracks must be properly prepared to ensure the new cement will bond well. A standard concrete repair mix with a low water-to-cement ratio is typically used for this work.

The concrete may need to be replaced or reinforced for more extensive repair work. This requires a professional engineer experienced in concrete construction to design and implement the replacement or reinforcement. It is important to utilize proper reinforcement techniques and to tie the new concrete in with the existing rebar. Depending on the location of the defect, it may be desirable to use conventional concrete placement methods and to minimize differential shrinkage cracking between the new concrete and the existing concrete.

  1. Preparation

Before any concrete repair is undertaken, the existing surface needs to be thoroughly cleaned and saturated with water. This prevents water from interfering with the curing process of the new material and helps minimize differential shrinkage between the original and the repaired concrete.

The type of preparation required will depend on the extent and severity of the deteriorated concrete. It is important to ensure that the concrete surface is sound and that no major cracks or delaminations are present. A nylon brush may be sufficient to remove loose aggregate for minor damage. In severe cases, a power washer may be used. The concrete should be thoroughly rinsed afterward to ensure that any residual concrete and contaminants have been removed.

If you plan to use a topical concrete repair product, the existing concrete must have an acceptable bond with the new material. If the existing concrete has a high compressive strength, it is advisable to match that in your repair mix to avoid premature failure. Conversely, if the concrete has low compressive strength, beefing up the repair material with higher levels of cement will not improve its performance.

For repairs using a conventional concrete placement method, the depth and orientation of the defect is important. Thin sections of the damaged concrete will generate heat during curing that can cause thermal stresses to reach an unacceptable level, causing spalling and delamination of the repair. This can also be a problem with polymer materials.

If the existing concrete has a very low compressive strength, you must lower the water content in your repair mix to limit shrinkage cracking. This will require mixing a smaller volume of concrete and adding more coarse aggregate than normal. This will help achieve the proper slump for a smooth repair.

  1. Mixing

Concrete is a highly durable material with a limited lifespan and requires periodic repair. Concrete repair is a complex process involving removing existing damaged concrete and mixing and placing new concrete in the form of a patch or slab to replace it. The procedure requires high skill and experience to achieve the desired results.

A qualified contractor should be able to identify and classify the cause and severity of a concrete defect and determine the proper repair procedure. It is important to understand that major and minor defects require different repair methods.

For a concrete repair to be successful, the new concrete patch must have an integral bond with the base concrete. This is achieved using a low w/c and a higher percentage of coarse aggregate in the mix design. This will minimize shrinkage cracking. The concrete repairs should also be shaped to avoid the formation of thin patches at the patch edges. These shapes may include conventional form-and-pour, preplaced aggregate, or tremie concrete repairs, depending on the application.

The selected repair materials should be compatible with the intended in-place service environment and have sufficient constructability properties such as handling, rheology, and cure times. The chemistry of the repair material is also important to prevent corrosion of the steel reinforcement and provide adequate cover for existing coatings.

The increase in durability failures associated with concrete repair impacts the environment and society through the depletion of natural resources, waste generation, and user inconveniences. Engineers must design repair systems that attain specified performance levels with minimum impact. A concrete repair system should have a well-designed repair method, appropriate repair materials, and suitable installation techniques to meet the owner’s requirements.

  1. Application

If the repair is successful, it has to be placed in a way that makes an integral bond with the existing concrete. Several ways to achieve this include conventional placement, dry packing, and spraying.

Regardless of the chosen method, it is important to thoroughly clean and prepare the surface of the existing concrete before applying the repair materials. This is critical for both time efficiency and the long-term durability of the repair. Surface preparation methods may include detergent scrubbing, acid etching, grinding, abrasive blasting, shot blasting, scarifying, and bush hammering.

It is often necessary to form the repair concrete into a shape for larger repairs. This can be accomplished by hand raking or trowel spreading the material onto the existing concrete. A sprayer or pump can also be used to apply the repair material.

Using a repair product with a low water-to-cement ratio (w/c) is important. This will help minimize shrinkage cracking and promote good adhesion with the existing concrete. It is also a good idea to use a high percentage of coarse aggregate in the repair mix to help minimize shrinkage from hydration.

Another key element is to provide sufficient reinforcement in the form of steel bars or fibers. This will help prevent cracking and buckling in the future. If a structural concrete product cannot be repaired, replacement should be considered. This is especially true if the cracks are wide or running vertically through the product.

  1. Curing

Concrete repair must be properly cured to improve strength, durability, water tightness, and wear resistance. Proper curing also delays drying shrinkage cracking and ensures the repairs are strong enough to meet design requirements.

The key to successful repairs is a thorough concrete cleaning, adequate moisture, competent application of the repair material, and acceptably finished exposed surfaces. Surface defects such as honeycombing, sand streaking, and form joint offsets can be repaired using conventional placement methods. However, other repair techniques are needed for major concrete repairs or to improve existing structural properties.

Conventional replacement concrete involves pouring a new layer of concrete to replace the damaged section. This requires the repair concrete to be mixed to a low w/c with a high percentage of coarse aggregate to minimize shrinkage cracking. This is an acceptable solution for large sections of honeycombing but could be better for repairing cracks or other deterioration that extend through the concrete to the steel reinforcement.

For both types of concrete repair, the curing process is very important. It is recommended that curing be started immediately after finishing or within 30 minutes of placement if the mix has a low bleed rate. If the bleed rate is too high, a curing membrane should be used to slow down evaporation. This can be accomplished with polyethylene sheeting or concrete curing insulating blankets available at most DIY and hardware stores.

The amount of time that concrete takes to cure depends on the type of concrete and the mix used for it. Generally, the concrete’s packaging directions will indicate how long it should take to heal fully. The concrete must be kept moist during the curing process but can be covered if the weather is inclement. The cover should be removed once the concrete is fully cured (typically after 28 days).