Concrete Repair

The Basics of Concrete Repair

When a concrete structure becomes damaged, the first step is to conduct an evaluation and determine the cause of the damage. After this is completed, the appropriate repair method and materials can be selected.Concrete Repair

Contractors must select the right repair material—a product that will properly bond to existing concrete and develop good mechanical strength. For professional help, contact Concrete Repair Colorado Springs.

Before any concrete repair can begin, it must be determined what type of repairs are needed and the best way to accomplish them. The damaged concrete should be inspected for a variety of conditions, including structural integrity and surface condition. A non-destructive evaluation such as radar, impact echo, or infrared thermography may be able to reveal much of the information that is required without opening up the concrete.

If the damage is minor and only cosmetic, the surface can be repaired with a liquid coating such as epoxy. This is ideal for pitting, spalling, and small surface cracks. It is important that the concrete surfaces be cleaned before applying the epoxy patch. This will help prevent the new coating from adhering to any dirt or other materials that may be present.

Major structural concrete repairs should always be done by a qualified professional engineer experienced in concrete construction. Generally, structural repairs should involve breaking away the existing concrete to expose the reinforcement and allow for a full inspection of the concrete by a petrographer or by drilling core samples that can be analyzed in a lab.

Destructive testing is often used for large structural repairs, but it is also useful in determining the nature of the deterioration and what kind of concrete replacement or repair is necessary. Concrete replacement is normally recommended when there are major sections of honeycombing or cracks that extend beyond the reinforcing structure within the concrete.

Choosing the right repair material depends on several factors, including compatibility with the damaged concrete, availability, and cost. Typical repair materials include unmodified Portland cement mortar or grout, latex-modified Portland cement mortar or grout, quick-setting non-shrink concrete, and polymer concrete.

All of these materials have advantages and disadvantages, and the choice should be based on a thorough understanding of the specific requirements of the damage. For example, a good repair must be durable enough to resist weathering and chemical action, and it should have the same compressive strength as the original concrete. The bond between the old and new concrete must also be sufficient to support a design load.

Mixing

Concrete is one of mankind’s greatest inventions, but it can deteriorate over time. Fortunately, it’s easy to repair small cracks and honeycomb areas with specially formulated patch and repair materials. However, before these products can bond with the existing concrete, contractors should take steps to prepare the old concrete surface.

First, sweep the area to remove dirt and debris that may act as bond breakers. Then bring the area to saturated surface dry (SSD) by scrubbing, spraying, or using a power washer.

Once the surface is ready, it’s important to use the right mix for the job. For example, a repair mix needs to have low drying shrinkage and a high percentage of coarse aggregates to minimize early-age shrinkage cracking. It also must be self-priming to eliminate the need for an extra additive, such as a bonding agent.

Some manufacturers offer a wide range of prebagged mixes to suit different situations and structural requirements. These include mixes that are designed to be used in vertical applications, those that can set quickly, and those that are sculptable for application to corners and other difficult-to-reach places.

Contractors should also consider the properties of the existing concrete before selecting a repair material. Its compressive strength should be close to that of the existing concrete, and it should have similar elastic modulus and thermal coefficients. It should also be freeze-thaw-resistant to limit damage from ice-induced expansion and contraction.

The most critical consideration when choosing a concrete repair mix is the water-to-cement ratio. The higher it is, the more potential there is for early-age shrinkage cracking and the weaker the concrete will be. For this reason, contractors should use a low water-to-cement ratio mix when making repairs.

To reduce the amount of water in the repair mix, contractors can add a high-range water-reducing admixture to help maintain a proper mix design. This is especially important when repairing an existing structure. It’s recommended to attend concrete repair seminars from manufacturers like World of Concrete to learn more about mix designs and other critical aspects of concrete repairs.

Applying

Concrete repair is the process of restoring structural integrity to a damaged concrete structure by applying replacement concrete or other material. The most common repair material used for concrete is Portland cement mortar, or grout. It is easy to work with, affordable, and has good performance characteristics. Other materials, such as polymer concrete and rapid-setting non-shrink mortar, are also available for repairs. The choice of a repair material depends on the needs of the project and must be compatible with the existing concrete structure.

Before any concrete repair material is applied, the surface should be clean. This can be done with a broom, a hose, or by hand. In the case of major structural repairs, it is necessary to clean the entire area where the new concrete will be placed. This is best accomplished by sandblasting or shotblasting, although in some cases it is possible to simply hose off the area that will be receiving new concrete.

Using conventional concrete placement methods, the repair material must be able to bond effectively with the existing concrete. This is usually achieved by using a low water-to-cement ratio (w/c) and a high percentage of coarse aggregate in the mix. In addition, the concrete used in a repair should be free of voids and have good compressive, flexural, and abrasion resistance.

When repairing cracks, the objective is to create either a structural or a watertight bond. In order to achieve a structural bond, epoxy injection is a viable option. Injection should only be performed on structurally sound concrete, as the process is expensive and requires a skilled contractor. In addition, a urethane sealant can be used to create a watertight seal. This repair method is quick and simple, but it should not be used on active cracks as it does not create a strong structural bond.

Many homeowners and business owners do not realize the time, expense, and hassle associated with completely replacing large concrete slabs or sections of concrete. In addition to the cost and labor, this type of replacement can be disruptive to the operation of a business or a home. Our concrete repair services can provide a quick, cost-effective, and safe alternative to replacement projects.

Curing

Concrete repair requires proper curing for its strength to develop. Curing also delays drying shrinkage cracks that can occur in concrete at any time after placement and finishing. Curing is accomplished by maintaining water on the surface of concrete and preventing it from evaporating.

Several methods of concrete curing can be used, including wet coverings and misting or fogging. Wet coverings can be hessian, burlap, or canvas that are kept moist by continuous wetting with water. This method is especially useful on outdoor jobs in shady areas or in the winter. Other materials that can be used for concrete curing include sand, straw, and even earth that is periodically sprinkled with water. Care must be taken with these methods to prevent soil staining from excessive moisture.

For indoor jobs, a concrete curing mat or blanket is often used. These are made of porous material such as jute, netting, or cotton and provide an excellent seal to keep concrete moist and prevent it from drying out. This helps to reduce cracking, scaling, and spalling.

If using a concrete mix for repairs, it is important that the proper w/c (water-to-cement) ratio and percentage of coarse aggregate are used in order to minimize cracking. The use of replacement concrete is also possible for certain structural repair applications. However, this must be carefully designed with the help of a qualified professional engineer to ensure that it is able to form an integral bond with the existing concrete.

When repairing concrete, it is also important to remove any loose or cracked sections of the existing structure. Then vacuum, sweep, or hose down the area to make sure that it is clean and free of dirt and other materials that may interfere with the bonding process. This can be done with a heavy-duty hand trowel or with a sledge and cold chisel on large surfaces.