Concrete repair: types of damage and methods of their elimination

Although it is one of the most popular and long-lasting building materials worldwide, concrete isn’t unbreakable. Weather, large loads, or normal wear and tear can cause a variety of damages to concrete structures over time. It is essential to comprehend these kinds of damage in order to preserve the integrity and security of roads, buildings, and other structures.

Common problems like discoloration, spalling, and cracks can compromise the strength and usefulness of concrete in addition to its appearance. Ignoring these issues can eventually result in more serious harm and expensive repairs. It’s crucial to recognize them and take action against them as soon as they manifest.

This post will discuss the most typical forms of concrete damage and offer workable solutions for fixing them. There are efficient ways to get your concrete back to its original state, regardless of the severity of your structural problems or minor cracks. Let’s get specific and discover how to maintain the best possible condition for your concrete.

Types of defects and the reasons for their occurrence

Repairs are typically necessary for reinforced concrete structures that were built several decades ago. Poor-quality concrete was far more prevalent back then than it is now.

The technology used to produce artificial stone was extremely inadequate: the required thickness of the protective layer was not maintained, the water-cement ratio was not strictly adhered to, there was little control over the granulometric composition and quality of fillers, and the reinforcement is now simply exposed.

Such structures need to be thoroughly examined in order to produce an accurate "diagnosis," which includes taking detailed descriptions, drawings, and high-quality photos. Additionally, it is much simpler to make the correct decisions and select a restoration strategy when the original data with drawings is also available.

Reminder: It is crucial to determine the precise amount, location, and state of reinforcement when choosing materials for concrete repair in hidden structures. The electromagnetic device IZS will assist in locating the reinforcement in the concrete if the protective layer’s thickness is less than or equal to 9 cm.

You can see with your own eyes how different the damage can be from different sides when the structure is accessible for visual inspection.

• From the north, low temperatures have a greater impact, which means that the number of freeze-thaw cycles increases. From the south, sharp temperature changes occur more often, which can lead to the appearance of deeper cracks.
• New reinforced concrete structures may also require repair. Most often, such a need arises after their removal of formwork, when the defects resulting from poor-quality concreting appear in all their glory.
• This can be caused by both unsatisfactory quality materials and poor compaction of concrete. Sometimes a not entirely successful design solution does not allow for the full concreting of certain areas.
• Very often, defects are caused by worn-out formwork – an inventory option for multiple use. When a vibrator is in operation, cracks appear in worn-out formwork through which cement milk flows out, due to which the surface of the structure does not have a smooth surface, but a gravel one.

Methods for combating concreting defects

Every defect is separated into two categories:

1. In the first surface defects such as the same gravel surface or shallow cavities, build-ups and unevenness. It is not difficult to repair the surface of concrete – this does not require developing special measures or incurring significant costs.

1. In the second group defects such as voids, deep or even through cavities and cracks. And also, a big problem is the deviation of the resulting structure from the design parameters.

And these are the methods to get rid of them.

Removing imperfections from the surface

The following procedures are used to remove flaws that appear as a gravelly surface or a surface scattered with small shells:

1. If the surface is gravelly, it is cleaned with a steel brush, washed with water, and then plastered with a solution with volumetric proportions of 1 part Portland cement (M400-500) to 2 parts sand.
2. When it is necessary to remove sinks, they are removed using a chisel from loose concrete around the edges, after which a metal brush is also used, washing and caulking with a solution.

Note: The gunite method can be used to repair concrete walls or foundations for large volumes of work. We’ll go into further detail about this approach later.

1. Sludges of concrete must be removed immediately after removing the formwork, before the concrete reaches full strength. A chisel, pick or jackhammer is used as a tool.

Deep defects

One of the most prevalent defects, large cavities, are typically the result of concrete being dropped into the formwork from a height. They can also result from stratification and setting during long-term transportation, using an overly rigid mixture, or from inadequate compaction.

Large cavities

The areas with a high concentration of reinforcement or those where it is inconvenient to fill and compact the concrete within the formwork are the most vulnerable. In these situations, the quantity and size of the flaws are taken into consideration when choosing the concrete repair technology.

• In vertical load-bearing structures – for example: columns that operate under a high degree of load, cavities are cleared down to the reinforcement, and after washing with water, they are concreted.
• Fine-grained concrete on Portland cement M400-500, manufactured directly on site, is usually used for this purpose.
• It is important that the brand of the repair composition is an order of magnitude higher than the constructive – this is the only way to ensure their good adhesion.

Be aware that clearing the sink can significantly reduce the column’s bearing capacity if it is through. Consequently, it is first pre-reinforced with metal overlays, and only then is the cement solution pumped into the voids through the tube defect; alternatively, a reinforced concrete clip is placed around the outside of the structure.

Through voids

Vapors are a common defect in construction practice that arise when the use of formwork for concrete mixture is prohibited in a particular area.

• The size of the voids can be quite impressive – such that the reinforcement is even exposed. At the same time, due to the rupture of concrete, the monolithic structure is violated. How similar defects are eliminated?
• As in other cases, first the defective area is cleaned and washed. Then, where it is necessary to concrete, install a suspended formwork covering the upper joint and fill it with a mixture. Make concrete on fine-grained crushed stone, adding a hardening accelerator to it.
• Together with a representative of the construction laboratory, the builders check the quality of the mixture, and only then begin concreting. In places where defects are sealed, especially in winter, the concrete is heated with steam, infrared lamps or electric heating.

Large cracks

Cracks that develop as a result of soil settling, stresses brought on by temperature changes, and other forms of deformations are another major flaw in concrete. Solving such a problem is quite challenging, and typically, a representative from the company that designed the building is invited for this reason.

• A commission is created that must inspect the structures, identify the cause of the cracks, measure the size of their opening and establish through observation the fact of its progression.

Note: Installing gypsum beacons on cracks is the easiest way to manage their behavior.

• Stable cracks are sealed after expansion and cleaning, by pumping mortar into them under pressure or by spraying (dry gunning).
• If it is established that the cracks continue to expand, the designers are required to urgently develop a project to strengthen the defective structure.

Following the completion of the work by the construction organization, each one is formalized through a corresponding act.

What is gunning

Throughout the narrative, we mentioned that gunning can be used to remove surface defects in concrete. It is time to elucidate what it is a little bit more.

• Shotcrete is actually plaster, a layer of mortar applied to the surface by spraying under high pressure.
• At the same time, it fills all the smallest cracks and pores, which contributes to the highest adhesion to the base surface.
• The applied layer can be quite thick, so there must be a wire or reinforcing mesh underneath it. What exactly – it depends on the scale of the work being done.
• Before installing the reinforcement, cracks on the surface are treated with a sandblasting machine or a strong water jet to remove loose concrete and dirt.

• Shotcrete concrete can be made either on Portland or alumina cement, and it can be applied either dry or wet.
• In the first case, the dry mixture is loaded into the unit (gun) and fed by compressed air through a nozzle, in which humidification occurs. It is this method that allows you to apply thick layers of concrete when repairing structures in just one pass.
• With the wet method, the shotcrete composition is pre-mixed with water, mixed and fed to the place of application by a pump. With wet application, less dust and lower loss of mortar due to rebound. This method ensures a more uniform application of the mixture, which is very convenient when you need to get a thin layer of shotcrete during repairs.

Reinforced concrete that has been damaged can be repaired using either technique. Additionally, they can be used to restore old stone or brickwork, strengthen the pit’s walls, and fix the foundation.

In order to preserve the longevity and safety of structures, concrete repair is necessary to address a variety of damage types, including surface deterioration, cracking, and spalling. Resurfacing, applying specialized sealants, and patching are all efficient ways to get rid of these problems, depending on the kind of damage. By using these methods, concrete can be made stronger and more resilient over time, avoiding expensive repairs and structural failures.

Despite being a strong and adaptable material, concrete can sustain damage over time, even with the best care. Concrete structures are susceptible to common problems that can impair their integrity and appearance, such as surface deterioration, cracking, and spalling. Maintaining the longevity and safety of any concrete construction requires an understanding of the different types of damage and how to address them.

In order to detect damage early, routine inspections are necessary. Simple sealants or fillers can frequently be used to fix small cracks, stopping them from growing and creating more serious issues. It might be required to use professional repair methods like epoxy injections or resurfacing for more serious problems like deep cracks or spalling.

Environmental variables that frequently cause concrete damage include chemical exposure and freeze-thaw cycles. Applying sealants and using protective coatings are two examples of protective measures that can help lessen these effects and increase the concrete’s lifespan. Future damage can also be avoided by minimizing heavy loads on concrete surfaces and making sure proper drainage is in place.

In the end, prompt and efficient repairs not only preserve the structural integrity of concrete but also result in long-term cost savings by averting more involved and expensive solutions. Proactively repairing and protecting your concrete is a smart investment in the longevity and safety of your construction projects, regardless of the severity of your concrete cracks or structural problems.

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