Concrete cracks are a frequent problem that many builders and homeowners deal with. Numerous factors, including shrinkage that occurs naturally during the curing process and external forces like temperature fluctuations or ground movement, can cause these imperfections to manifest. Whatever the reason, if you don’t fix cracks right away, they can weaken your concrete structures’ structural integrity and aesthetic appeal.
Preventing cracks begins with understanding why they occur. In certain instances, they may be purely superficial and not really dangerous, but in other situations, they may trigger more significant structural issues. You can choose the best method to repair the crack and avoid more problems by figuring out its type and cause.
This post will walk you through the most typical reasons why concrete cracks and offer helpful tips on how to repair them. Knowing the proper technique can help you avoid wasting time, money, or frustration on fixing tiny hairline cracks or larger, more serious fractures.
| Cause | Fix |
| Shrinkage due to rapid drying | Keep concrete moist during curing and use shrinkage-reducing admixtures |
| Heavy loads or poor design | Reinforce the area with steel bars or fiber reinforcement, and repair cracks with epoxy injection |
| Freeze-thaw cycles | Use air-entrained concrete and seal the surface to prevent water penetration |
| Soil movement or settling | Repair with flexible sealant or use underlayment to stabilize the area |
Cracks in concrete: causes of occurrence
It is essential to take into account the different kinds of defects and their causes in order to gain a deeper comprehension of crack repair technologies. Concrete cracks are categorized based on the following criteria:
- Depth of damage: hairline, through, surface.
- Direction of cracks: vertical, inclined, horizontal, curvilinear and closed.
- Type of concrete destruction: shear, shear, rupture, crushing.
Causes of the deterioration of concrete material:
- Shrinkage. Shrinkage cracks in concrete are the result of incorrect proportions of components when preparing the solution or improper care of the freshly poured structure. This type of damage appears in the absence of a load and is characterized by: small opening (up to 2 mm), uniform distribution along the entire length of the structure.
- Temperature drops. With a concrete structure length of 100 meters, a change in ambient temperature by 1 degree Celsius causes a change in linear dimensions by about 1 millimeter. Due to the fact that during the day the temperature differences can reach 15 degrees or more, concrete cracks. To eliminate this harmful phenomenon, the technology of "temperature joints" is used. In this case, the distance between the temperature joints is calculated individually depending on the dimensions of the structure and other factors.
- Settlement. Uneven settlement of concrete foundations and walls poses a serious danger to newly built structures. Settlement is the cause of the "worst" inclined cracks. To prevent uneven settlement, it is necessary to strictly follow the technology of soil preparation and erect the building box (load the foundation) after natural settlement – 12 months after pouring.
- Heaving. The phenomenon of soil heaving occurs in the winter. Frozen soil tries to "push" the building out of the ground, as a result of which very serious damage can occur. As practice shows, linear displacements of a building as a result of heaving can reach 15 centimeters. You can prevent the formation of cracks from heaving by the correct depth of foundation embedment below the maximum soil freezing level in a given area.
- Corrosion of steel reinforcement and incorrect reinforcement. According to the laws of chemistry, corroded metal increases in volume and, accordingly, begins to "tear" concrete. Also, the appearance of cracks can be caused by an incorrect calculation of the reinforcement belt.
Repair of cracks in concrete
The current regulatory document, SNiP 52-01-2003, regulates the width of crack opening in concrete. Concrete cracks are permitted by SNiP up to the following restrictions:
- Based on the condition of preserving the reinforcement: up to 0.3 mm with prolonged opening and up to 0.4 mm with short-term opening.
- Based on the condition of concrete permeability: up to 0.2 mm with long-term opening and up to 0.3 mm with short-term opening.
- For large-scale hydraulic structures: up to 0.5 mm.
A wire brush can be used to remove hairline cracks in concrete that has already hardened and set. In order to seal cracks in concrete that hasn’t started to set and harden, you can either use cement-sand mortar, which is made up of one part Portland cement and three parts sand and rubbed into the defects with a trowel or spatula, or you can apply more vibration until the damage is completely removed.
Concrete cracks are a common problem that can be caused by a number of things, such as inadequate curing, temperature fluctuations, or structural stress. Choosing the appropriate repair technique—whether it be using sealant to fill in small cracks or addressing more serious structural issues—requires an understanding of the underlying causes. By quickly filling in cracks, you can save additional damage and increase the longevity of your concrete surfaces.
Crack sealing agents
Special repair compounds are used to seal cracks in concrete that has already fully set and hardened as well as cracks in concrete that is on the street. The most widely used concrete crack repair compounds are:
- Concrete composition. Considered most preferable for eliminating wide and extensive damage. For the preparation of concrete repair composition, sand and straining cement with low energy of self -expression (NC20) are used. The sealant is styrene-butadiene latex, which ensures water resistance and adhesion to the base. The ratio of cement and sand, as well as the size of the sand, depend on the dimensions of the damage. 1:1 for cracks up to 0.3 mm wide (maximum fine sand or dolomite flour), 1:2 for defects from 0.3 to 3 mm (sand with a fraction size of up to 0.1 mm), and 1:3 for damage wider than 3 mm (river sand with a fraction size of 1.5 mm). The amount of sealant is taken as 40-45% of the weight of cement.
- Composition based on ED-20 epoxy resin, IMTGFA hardener and sand (dolomite flour or limestone flour. The resin is mixed with the hardener in a ratio according to the attached instructions. Then fine sand is added to the composition in a ratio of 1 part resin and 1 part sand according to volume and fill the crack in any convenient way: with a spatula, trowel or knife.
- Liquid glass. Liquid glass for sealing cracks in concrete is used in a mixture with cement and sand as a sealant. In essence, liquid glass is a budget analogue of epoxy resin and before mixing with cement and sand it is diluted in a ratio of 1 part liquid glass to 2 parts water.
- A special repair compound for sealing cracks in concrete, offered by manufacturers and retail chains: "REPER", Lugato 5-Minuten Mortel (Schneller Mortel) and "Klei Konstanta Granito".
Because it calls for specific technological tools and materials, the injection method of fixing concrete cracks "is" a distinct process.
The process of injecting cement or polymer mixtures containing specific additives into cracks is the fundamental technical aspect of the crack injection method. In this instance, the concrete crack sealing mixture fills in all the damaged areas and firmly seals the building.
Conclusion
Taking a look at the present issue of sealing concrete cracks, we can observe the following fundamental ideas. Repair compounds must meet the requirements of climatic conditions, water resistance, and minimal shrinkage after polymerization or hardening. Cracks must be carefully expanded and cleaned.
Although concrete cracks can be annoying, they frequently occur naturally as a part of the material’s life cycle. It is easier to take the appropriate action to prevent and repair them when you are aware of the causes, whether they are structural problems, drying shrinkage, or temperature variations.
Crack repair doesn’t have to be difficult. Many repairs can be completed without the assistance of a professional if the proper tools and knowledge are used. If you take care of a small crack or something larger early on, it will stop more damage and maintain the best possible appearance and functionality for your concrete.
Maintaining the integrity and aesthetic appeal of your concrete surfaces will largely depend on routine maintenance and being vigilant for the first indications of cracking. You can benefit from strong, long-lasting concrete for many years to come if you take preventative measures.
