How to Repair and Prevent Concrete Cracks
Concrete is one of the most common materials used for structures, especially in urban areas. Its outstanding properties such as its durability, fire resistance, longevity, etc., it is best used for roads, bridges, buildings, and other structures. Although it probably one of the most robust materials in the construction industry, it is still susceptible to damages such as cracks. Cracking is one of the Major Causes of Broken Concrete, and the reasons why it can happen are quite numerous, but so are the ways to repair and reinforce them. The following is an in depth guide on how cracking happens and what you can do to mitigate it.
Causes of Concrete Cracks and How to Prevent Them
Multiple internal and external effects cause concrete to crack, such as temperature changes, heavy loads, earth movement, and possible errors during the curing process. Although the chance of predicting if a concrete structure will develop cracks, the effectiveness of prevention measures is promising. To avoid having to deal with concrete cracks, here are a few common causes and prevention methods that might be helpful to you:
Plastic Shrinkage. This defect commonly happens during the last stages of curing, wherein the concrete is still in a plastic state. When the water in the mix is evaporating rapidly, defects appear as thin cracks appear on the concrete’s surface. The best way to prevent concrete cracks from forming is to make sure that your cement mix’s water-cement ratio is accurate. Another method that works for most is performing fog sprays to prevent excessive evaporation. It also helps to cover the poured area with materials such as polyethylene sheets.
Heaving. Movement beneath the concrete structure such as earthquakes, over hydrated soil, or even growth of tree roots around the concrete typically causes cracks. This type of cracking is tough to avoid, primarily because it is commonly caused by natural circumstances, especially for concrete located outdoors, such as roads and sidewalks, wherein all sorts of pipes are underneath. It is almost impossible to be protected from rainwater. The only way to effectively prevent concrete cracks is to carefully plan the concrete area’s location and remove anything that might cause movement underground if possible.
Temperature Changes. Cracks usually occur when portions of the concrete experience a temperature difference. Since volume changes in concrete are possible depending on temperature, applying different temperatures in different sections results in varying volume changes across the whole concrete area. Especially in thicker sections of concrete, the inside cools slower than the concrete’s outside layer. This causes a greater possibility of tensile stress to occur from the interior section, ultimately causing cracks in the concrete’s surface. Using low-heat cement is a tested way to prevent concrete cracks due to temperature. Insulating the surface of the concrete during the first few days of cooling may help as well.
Overloading. Even if the concrete section is well designed and built according to building codes, it will still be subject to a maximum load limit. When load applied exceeds the limit, concrete will most likely be damaged, causing cracks or destruction of the structure. Using high-strength concrete is one of the best options to prevent overloading cracks. But without comprehensive research and careful design, concrete will never be able to withstand the load required for its intended use.
Ways to Repair Concrete Cracks
Since concrete is a material that expands when in contact with heat, it is nearly impossible to prevent it from cracking in its lifetime. The good thing is there are ways on how to repair cracks on your structure. Listed below are some methods that have been proven to be effective in repairing cracks:
Grouting. This method can be used in small cracks and even large ones, so it is the most common repair method used in the industry. The grouting process starts by cleaning the cracks for debris stuck in between them, followed by the installation of grout nipples (or similar materials) and the grout, cement paint, or sealant application. After grouting, the cracks are flushed out to make sure that the grouting was successful. For larger concrete structures, Portland cement is typically used to cover up cracks. Epoxy may also be used but is more expensive compared to cement. That is why it’s rarely used for larger structures. For more minor cracks, a manual injection gun would do the job. If the crack is wider, there will be a need to use a powered machine pump.
Surface Treatment. Hairline cracks are almost unnoticeable and fragile cracks. Especially for concrete surfaces that do not carry heavy loads, a standard repair method is by first clearing the crack from debris by brushing or air blowing. This is followed by injecting or pressing any filler like epoxy or concrete into the crack itself.
Structural Reinforcement. If a concrete structure has defects internally, the only way to repair it is by installing additional structural reinforcements. This method is typically used in infrastructures such as old bridges subject to heavy loads such as trucks and high volumes of pedestrians. In fixing concrete cracks in these kinds of structures, the process usually begins by drilling holes that intersect the cracks. This is followed by the injection of the epoxy in the gaps and then the installation of steel reinforcements (also known as anchors). After which, the reinforcements and the whole crack are then sealed by more epoxy. In modern engineering, pre-stressed strands could also be externally installed to allow compressive force to hold the cracks together.
Although there are already multiple methods on how to repair concrete cracks, not all cracks are needed to be sealed. As discussed in this article, some cracks are caused by more serious structural defects that may need to be repaired prior to sealing the damage. If the cause of the cracking is not identified correctly, chances are the cracks will reappear and may eventually lead to worse damages compromising safety and resulting in high costs. That is why it is essential to know the different causes of concrete cracks to properly assess the damage before applying any suggested remedies mentioned in this article.
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