The Basics of Concrete Repair

Concrete repair begins with a thorough evaluation to determine the condition of the structure. Then, a suitable method and materials can be selected.

Concrete Repair

Preparation of the repair area includes saw cutting of the concrete perimeter in good shape, cleaning and coating of reinforcement steel, application of bonding agent on the existing concrete surface, cleaning of loose debris, and preparation of patch mix. For professional help, contact Concrete Contractors Colorado Springs now!

Concrete cracks are unsightly and can lead to costly repairs if not repaired quickly. They can also pose a health and safety risk for the people walking on them and increase the chances of water ingress. Cracks that are not repaired can deteriorate further and expose reinforcement steel to corrosion, which can lead to the failure of the concrete structure.

It is important to distinguish between dormant and active concrete cracks in order to select the best repair method. Dormant cracks are not expected to move further and can be repaired by routing and sealing the crack using a suitable filler. This is a good method for dormant cracks that are not leaking, but if they start to leak, it is best to reroute the crack and use a waterproof sealer.

Plastic shrinkage cracks (usually 1 to 2 mm wide) may self-heal through continual cement hydration or the precipitation of calcium carbonate. These cracks are usually shallow and do not penetrate the full depth of the concrete slab. However, if the cracks are widening, it is important to treat them as expansion and contraction joints and seal them to prevent further movement of the concrete slab or water ingress.

Non-dormant cracks that are leaking should be repaired by injecting a polyurethane resin into the crack to stop the leak. This type of repair is effective for wet and leaking cracks and can be used on both dormant and active cracks.

For active cracks, a more permanent solution is to drill and plug the crack with grout or epoxy. This technique involves drilling a hole the width of the crack and then filling it with the appropriate filler material. The grout forms a key, locking the crack and preventing further movement of nearby concrete sections. This method can also be used on wet cracks if sealed with moisture-tolerant epoxy.

Concrete cracks are an inevitable part of the aging process and should be repaired as soon as possible to reduce cost, health and safety risks, water ingress, and deterioration of the concrete surface. Repairing cracks in concrete sidewalks, driveways, garage floors, and patios is easy with the right tools and the correct patching materials.


The extent of concrete damage—the degree to which it has affected the serviceability and safety of the structure—must be determined before a decision is made on whether to repair or replace the damaged structural member. If the damage is deemed significant and the structure needs repair, a cost-benefit analysis should be performed to determine the feasibility of the repairs and compare these costs with the cost of replacing the damaged structural member.

Concrete deterioration can occur due to many factors, including physical action, chemical action, and environmental conditions. These factors can cause cracking, spalling, sagging, corrosion of reinforcement, and loss of load-carrying capacity. The deterioration process can be accelerated by poor placement of concrete, a high water-to-cement ratio, improper curing methods, and the timing of control joint installation.

A good repair should restore the structural integrity of the damaged concrete and provide a safe, serviceable condition for users. This can be achieved by following best practices for repair, protection, and strengthening (RPS). These include evaluating the cause of damage, documenting the repairs with before and after photos, confirming that surface preparation is acceptable, including sounding the surface for cleanliness and amplitude, using only materials tested by a qualified testing agency, and performing sounding or direct tensile bond tests on the cured repair to ensure good adhesion.

The durability of repaired concrete is important and must be a priority for any project. Unique offers a wide variety of repair materials that can be used in concrete repairs, including unmodified Portland cement mortar or grout, latex-modified Portland cement mortar or concrete, quick-setting non-shrink concrete, and polymer concrete. The most critical factor for achieving durability in repaired concrete is the adhesion between the repair material and the existing concrete substrate. The higher the adhesion, the lower the tolerance to incompatibility errors between the joined materials [42].

Durability is a combination of the structural properties of the concrete, including strength, stiffness, and permeability, as well as the properties of the repair material, such as its cracking resistance, drying shrinkage, modulus of elasticity, and freeze-thaw durability. When a repair is expected to last 25 years, it has a high probability of achieving this durability.


Almost all concrete repairs require adhesion between the new material and the existing concrete substrate. The adhesion must be strong enough to overcome a significant amount of drying shrinkage stress and a relatively high amount of corrosion (from chloride ingress) in a very short period of time.

Achieving a good bond between the new and old concrete is a complex task. A good bond depends on the quality of the mix design, the surface preparation, the installation procedure, and the curing practices. It also depends on the condition of the existing concrete. Typically, the better the original condition of the concrete, the easier it is to achieve a good bond.

Adhesion can be enhanced by pre-cleaning the concrete to remove loose particles or other materials that may interfere with adhesion. This can be done with a wire brush, broom, or even a power washer in some cases. It is also a good idea to dry the concrete as much as possible before applying the repair material. This is especially important when working in a damp environment, where it may take longer for Mother Nature to dry the repair area.

The use of a chemical densifier or bonding agent is also often recommended for new or old concrete surfaces. These materials penetrate the concrete to release the free lime and hydrate the surface to improve the tensile strength of the cement-to-aggregate bonds. This increases the durability of the repair in the long term.

In addition, the selection of a repair material with the right properties for the service conditions of the concrete repair is critical. This includes handling properties, rheology, and cure times. Repair materials come in many forms, including ready-mix concrete delivered from a local plant, site-batched concrete from a mobile mixer, and a wide range of formulated bagged concrete repair mortars and cements.

The best repair materials will have a low water-to-cement ratio and will be able to set in the most difficult environments. They should have a good abrasion and skid resistance rating to reduce the possibility of premature wear on the repaired surface, and a high strength for the long-term durability of the repairs.


Concrete repair materials must have sufficient strength to withstand the load and stresses to which they are subjected. This is a factor in the design of new concrete structures and the repair of existing ones. It is also an important issue for the longevity of the repairs.

Different types of repair materials are used for different types of structural damage and environmental conditions. They include unmodified Portland cement mortar or grout, latex-modified Portland cement mortar or concrete, quick-setting non-shrink mortar, and polymer concrete. Besides these, epoxy, impregnant, and zinc-rich coatings are also effective repair materials.

Contractors should be familiar with all the options available and choose the material best suited to the project at hand. This will ensure that the repaired concrete has a long service life and meets its design requirements.

The type of repair material and the way it is applied will affect the quality of the finished job. The surface of the existing concrete must be clean, free of mud, oil, grease, and other contaminants. A wire brush may be used to remove any loose particles that could hinder the bond between the old and new concrete.

In addition to a good bond between the repaired and existing concrete, it is essential that the repair material have high durability, low water permeability, and be resistant to the corrosion of steel reinforcements. The material should also have a low coefficient of thermal expansion to minimize stress transfer between the repair and the adjacent concrete.

The size of the patch and its depth must be taken into account when determining the amount of repair material required. This is especially important for overhead repair jobs, where a thick section of concrete can cause sagging. For these reasons, it is important that contractors use prebagged shrink-compensated concrete and avoid feather edging, as this will flake off and leave gaps in the repair.

Another important consideration is the curing regime of the concrete repair. If the concrete is not adequately cured, it will take longer to reach its full strength and will be less durable. Various repair materials require different curing conditions, and some need to be kept in a protected environment without exposure to water until they achieve the desired strength.