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8 Ways to Prevent and Repair Random Cracks in Concrete

The sight of a newly laid concrete slab marred by random hairline fractures can be disheartening to contractors and clients alike. Cracks in concrete slabs not only compromise structural integrity but also have aesthetic and functional repercussions.

In the construction industry, addressing this challenge is paramount, as concrete is one of the most widely used materials for its durability and strength. Whether it’s a foundation, a sidewalk, or a prestressed bridge, the integrity of concrete is crucial.

In this comprehensive guide, we will explore the common causes of concrete cracks and provide a detailed overview of how to stop them from occurring. Moreover, we'll share our top remedial techniques that construction professionals can utilize to ensure solid, concrete crack-free structures.

The Importance of Preventing and Repairing Cracks in Concrete

Before we dig into the preventative measures, it’s instrumental to understand the rationale behind taking the time and effort to avoid and fix concrete cracks. For starters, cracks can be an indicator of larger structural issues, which, if left unchecked, can lead to extensive deterioration.

In addition to structural concerns, visual imperfections in concrete can lead to reduced property value and an unprofessional appearance. Cracks can also facilitate the penetration of water, chemicals, and other harmful agents, causing further degradation of the concrete and any underlying steel reinforcements.

By proactively implementing the strategies outlined below, construction professionals can not only save on repair costs but also build a reputation for delivering high-quality, durable structures that stand the test of time.

Types of Concrete Cracks

Before we delve into the prevention and repair methods, it’s crucial to understand the different types of concrete cracks that can occur. These include:

  • Plastic shrinkage cracks: These occur during the initial curing stage when excess water evaporates, causing the concrete to contract.
  • Settlement cracks: As the name suggests, these are caused by uneven or inadequate soil compaction beneath the concrete slab, leading to settlement and subsequent cracking.
  • Overloading cracks: This type of crack results from placing too much weight or pressure on the concrete before it has fully cured.
  • Drying shrinkage cracks: Similar to plastic shrinkage cracks, these occur as the water in the concrete evaporates during the curing process. However, unlike plastic shrinkage cracks, drying shrinkage cracks occur after the concrete has hardened.
  • Thermal cracking: Extreme temperature fluctuations and differential heating can cause thermal cracking in concrete.

Understanding the underlying causes of these cracks can help construction professionals take proactive measures to prevent them from occurring in the first place. However, should cracks still appear despite preventative efforts, there are steps that can be taken to repair them effectively.

effective ways to prevent random cracks in cocnrete

8 Effective Ways to Prevent Random Cracks in Concrete

1. Proper Concrete Mix Design and Material Selection

The foundation of durable concrete starts with a meticulous mix design. Adjusting the mix proportions can significantly enhance the concrete’s resistance to cracking. Employing the correct ratio of cement, water, aggregates, and admixtures can result in a more workable mix with adequate strength and reduced shrinkage potential.

Using high-quality materials that conform to standards to prevent the risk of temperature cracks and fine aggregates with controlled particle sizes for workability can also contribute to a more homogeneous and robust concrete.

2. Adequate Curing Methods

Curing is essential to maintain adequate moisture and temperature in the concrete during its early life. Proper curing can prevent premature drying and shrinkage, which, as mentioned, are common culprits behind cracking.

Contractors can employ several curing methods, such as ponding, wet coverings, or chemical curing compounds. At the end of the day, it's all about ensuring the concrete retains the required moisture content for an appropriate duration.

3. Seasonal Considerations and Weather Protection

Concrete is sensitive to temperature and humidity changes during its curing process. Extreme weather conditions can cause rapid drying or prolonged setting times, leading to cracks due to uneven shrinkage.

With that being said, It's really important for contractors to keep an eye on the weather when they're pouring concrete or finishing projects like a concrete driveway. The use of windbreaks, sunshades, or temperature controls can help mitigate the effects of weather on the concrete.

4. Quality Control and Inspection

Adhering to strict quality standards is crucial to prevent potential cracking. This includes rigorous inspection of materials, concrete placement, and curing practices.

On-site supervisors and quality controllers should be vigilant, looking for early signs of trouble, such as excessively wet or dry concrete, poor compaction, or inadequate curing. Rectifying these issues promptly can prevent further complications and contribute to crack-free concrete.

5. Correcting Poor Workmanship

Sometimes, the presence of cracks can be attributed to poor workmanship. In such cases, corrective measures may include removing and replacing the affected concrete.

Investing in ongoing training and providing clear procedures for concrete placement, finishing, and curing can elevate the quality of work and reduce the incidence of random cracks.


6. Use of Reinforcement

The inclusion of reinforcement, such as control joints or steel rebar, can help to distribute loads and prevent cracks from forming. Fibers in the concrete mix can provide a three-dimensional reinforcement at the microscopic level, reducing crack widths and controlling their propagation.

In larger structures, traditional steel reinforcement adds tensile strength to the concrete, which is its inherent weakness. The correct placement and sizing of reinforcement are as vital as the material itself in preventing cracking.

7. Advanced Technologies for Concrete Crack Prevention

Innovation in construction materials is continually advancing the fight against concrete cracks. Self-healing concrete, for example, uses encapsulated chemicals or bacteria within the concrete mix to repair micro-cracks before they become problematic.

Other advancements, such as nano-technology admixtures or sophisticated void-filling techniques, are also emerging as promising strategies to prevent and mitigate the impact of concrete cracks.

8. Proactive Maintenance and Regular Testing

Preventative measures don’t stop at the construction stage. Regular inspection and maintenance of structures can catch potential crack sources before they become a significant problem. Non-destructive testing methods such as ultrasonic, radar, or infrared thermography can detect subsurface damage and anticipate areas prone to cracking.

Setting up a schedule for periodic maintenance and inspection can be just as critical as the initial preventative measures implemented during construction.

The Process of Repairing Random Cracks in Concrete

Despite best efforts, cracks can sometimes appear in concrete. Timely and proper repair is essential to maintain the integrity and appearance of the structure. Understanding the process of repair ensures that the right methods are deployed when needed.

First: Evaluate the Crack

First, you'll want to evaluate the type of crack. Not all cracks are the same, and each necessitates a tailored approach to repair. It's important to carefully evaluate the crack in terms of its width, depth, and the nature of the surrounding material.

Narrow cracks may be adequately addressed with low-viscosity epoxy injections, while wider ones may require routing to create a wider patching area. On the other hand, deep fissures may involve additional structural evaluation and repair.

Second: Decide What Method You'll Use

Several repair techniques are commonly used to mend cracked concrete. Non-structural hairline cracks may only require a surface sealer, while more severe or wide cracks may require the removal of debris and application of bonding agents before filling and smoothing with appropriate repair mortar.

Specialized materials such as polymers, mortars, and epoxies offer a variety of solutions for different types of cracks. The proper material selection, along with precision in application, is critical to the longevity of the repair.

Third: Take Preventive Measures

The repair process should also trigger a review of the surrounding factors that may have led to the crack. Implementing additional preventive measures can help avoid recurrences.

Certain areas may require the installation of supplementary reinforcement or the adjustment of control joint placement. Strengthening the substrate or modifying load distributions can also be part of the solution to prevent future cracks from developing.

how industrial grinders come to the rescue

Where Industrial Concrete Grinders Come to the Rescue...

Industrial concrete grinders are a go-to tool for preparing and repairing concrete surfaces. These powerful machines feature rotating discs or planetary heads fitted with abrasives such as diamonds, making them highly effective in removing surface imperfections.

Onfloor's concrete grinders thrive in versatility, equipping users to grind, polish, and remove coatings from concrete floors... all with one machine.

Preparing Surfaces for Concrete Repair

Before any repair work can be done, the damaged concrete surface must be prepped. Industrial grinders are ideal for this task as they can efficiently remove any existing coatings, adhesives, or contaminants from the surface.

They can also level uneven surfaces and create a rough profile to ensure proper adhesion of repair materials. Without proper surface preparation, any repairs will not adhere well and may fail.

For preparing surfaces, we recommend the low-speed OF16S-L. This multi-purpose machine is designed to resurface decks, sand wood floors, and, most of all, grind concrete.

Removing Damaged Concrete

Industrial grinders are also an effective method for removing damaged concrete. This is especially useful for large areas or deep cracks that require significant removal.

For this task, we recommend our high-speed OF16S-H. It is designed to grind up to 2 times faster than traditional grinders and can quickly remove material without creating additional damage.

Creating Smooth Surface

Once the damaged concrete has been removed, industrial grinders can then be used to smooth and finish the surface. This creates a seamless transition between the repaired and original areas, enhancing the overall appearance of the structure.

For polishing concrete, we recommend Onfloor's OF20S-H. The high-speed OF20S-H machine operates at 1,000 RPM, making it the ideal concrete floor polisher, capable of production rates as high as 500 square feet per hour.

Preventive Maintenance with Industrial Grinders

Properly maintaining concrete surfaces is essential to prevent cracks from forming or worsening. Regular grinding can remove minor imperfections before they become larger issues, extending the lifespan of the concrete.

In addition, industrial grinders can also be used for preventive maintenance on structures such as bridges or highways. By grinding down rough surfaces, they improve skid resistance and increase overall safety.


The prevention and repair of concrete cracks are multifaceted tasks that require a combination of technical understanding and practical wisdom. By implementing the outlined preventive measures and being aware of the repair process, professionals can transform what once might have been a serious construction issue into a manageable part of the building lifecycle.

Moreover, staying informed, open to innovation, and committed to quality is the surest path to crack-free, lasting concrete structures... and what better way to do that than with Onfloor?