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Cracking in Concrete: Causes and Solutions

Written by

Selwa Lukoskie

Published on


Concrete cracking is a persistent issue in construction, often caused by factors ranging from shrinkage and thermal changes to improper strength and load application. 

Concrete shrinks when water evaporates, causing it to contract and form cracks. Similarly, fluctuations in temperature can  lead to expansion and contraction, resulting in structural fissures. 

Addressing these issues requires a strategic blend of preventative measures and remedial actions. At RyanCo Concrete, we are committed to delivering high-quality concrete solutions, ensuring durability and longevity in every project we undertake.

What are the common causes of cracking in concrete?

Concrete can crack for many reasons factors, and common causes of concrete cracking include: 

  • Shrinkage: Concrete undergoes volume changes as it cures and dries. Shrinkage cracks result from the contraction of the concrete as it loses moisture. These are often fine surface cracks and are considered normal.
  • Plastic Shrinkage Cracks: These cracks occur when the surface of freshly poured concrete dries and hardens quickly due to factors like high temperatures, wind, or low humidity. Rapid surface drying can lead to cracks.
  • Drying Shrinkage: Concrete can continue to shrink over time as it dries out, leading to cracks. Proper curing and moisture retention can help mitigate this type of cracking.
  • Temperature Changes: Cracks can result from temperature changes in massive concrete structures like bridges and pavements. Proper design and expansion joints can reduce temperature-related cracking.
  • Overloading: Excessive loads or point loads that exceed the concrete’s capacity can cause cracks. Proper structural design and reinforcement help prevent this.
  • Settlement: Uneven settling of the underlying soil or subgrade can cause differential settlement cracks in concrete slabs and foundations.
  • Corrosion of Reinforcement: Corrosion of steel reinforcement within concrete can lead to cracks and structural deterioration.
  • Chemical Reactions: Some chemical reactions, such as alkali-aggregate reactions (ASR) and sulfate attacks, can cause cracks by damaging the concrete’s structure.
  • Poor Workmanship: Inadequate concrete placement, consolidation, finishing, or curing practices can result in cracks.
  • Freeze-Thaw Cycles: In freeze-thaw-cycle regions, water can enter cracks, freeze, and expand, causing further cracking and deterioration.

Proper design, mix proportions, reinforcement, curing, and construction practices are crucial to prevent or manage concrete cracking. Addressing the specific causes of cracking in each situation is essential to ensure concrete structures’ long-term durability and performance.

How can temperature fluctuations lead to cracking in concrete structures?

Concrete, a widely used construction material, is susceptible to temperature changes, which can crack. As temperatures rise, the concrete expands, and as the temperature drops, it contracts. 

Constantly expanding and contracting like this can lead to stress within the concrete, leading to the formation of cracks over time. This is particularly common in structures exposed to wide diurnal temperature swings without adequate thermal expansion and contraction provision.

In addition, the water within the concrete can when the temperature goes below freezing, causing it to expand by up to 9%. When temperatures rise, ice melts and water flows contracts, leaving a void. 

The continuous freeze-thaw cycle can lead to significant internal pressure build-up, leading to surface flaking or scaling and, eventually, cracking. Therefore, temperature fluctuations significantly threaten the longevity of concrete structures.

Are there different types of cracks in concrete, and if so, what are they?

Yes, there are different types of cracks in concrete, each caused by distinct factors and exhibiting unique characteristics:

  • Shrinkage Cracks: These are fine surface cracks produced by concrete curing shrinkage and loses moisture. They are common and generally not a structural concern.
  • Plastic Shrinkage Cracks: Rapid surface drying of freshly poured concrete due to factors like high temperatures, wind, or low humidity can lead to these early-stage cracks on the concrete’s surface.
  • Drying Shrinkage Cracks: Over time, as the concrete continues to dry and contract, additional cracks may develop, especially without proper curing.
  • Settlement Cracks: Uneven settling of the underlying soil or subgrade can result in cracks in concrete slabs and foundations, often as diagonal cracks.
  • Structural Cracks: These are typically caused by excessive loads, poor design, or inadequate reinforcement and may pose structural concerns.
  • Cracks Due to Corrosion: Corrosion of embedded steel reinforcement can cause cracks and weakening of the concrete structure.
  • Expansion Cracks: Occur due to thermal expansion and contraction, typically in large concrete structures. Expansion joints are used to control such cracking.
  • Chemical Reaction Cracks: Alkali-aggregate reactions (ASR) and sulfate attacks can result in cracks caused by chemical reactions within the concrete.

Identifying the type of crack is essential for determining the appropriate remediation or preventive measures in concrete structures.

What are some effective solutions for preventing or repairing cracks in concrete?

Effective solutions for preventing or repairing cracks in concrete include:

  • Proper Mix Design: Utilize an appropriate concrete mix design with adequate cement content, aggregate grading, and admixtures to enhance durability and minimize shrinkage cracking.
  • Reinforcement: Include steel reinforcement (rebar or mesh) to control cracking and improve structural integrity.
  • Control Joints: Install control joints or saw cuts to create weakened planes where cracks can occur predictably and in a controlled manner.
  • Proper Curing: Implement thorough curing practices to maintain moisture and promote proper hydration, reducing the likelihood of drying shrinkage cracks.
  • Crack Repair Products: Use epoxy or polyurethane-based crack repair products to fill and seal existing cracks, preventing moisture intrusion and further deterioration.
  • Structural Repairs: Engage structural engineers in assessing and repairing structural cracks, which may require additional reinforcement or remediation measures.
  • Surface Treatments: Apply surface treatments like sealers or coatings to protect the concrete from water ingress, chemicals, and environmental factors.
  • Expansion Joints: Install joints in large concrete structures to accommodate thermal expansion and contraction, minimizing cracking.
  • Preventative Maintenance: Regularly inspect and maintain concrete structures to resolve minor issues before they become major major cracks or damage.

By implementing these measures, you can enhance concrete’s longevity and structural integrity and minimize the risk of cracking or address existing cracks effectively.

Can improper construction practices contribute to cracking in concrete, and if yes, what are some examples?

Yes, improper construction practices can indeed contribute to cracking in concrete. Some examples of how these practices can lead to cracking include:

  • Inadequate Compaction: Poor compaction during concrete placement can result in voids and air pockets within the concrete, making it more susceptible to cracking.
  • Reinforcement Errors: Incorrect placement or spacing of reinforcement bars can weaken the concrete’s ability to resist tensile stresses, potentially causing cracks.
  • Improper Curing: Neglecting proper curing practices, such as insufficient moisture retention or early removal of curing materials, can lead to premature drying and cracking.
  • Overmixing or Undermixing: Deviating from recommended mixing ratios can affect the concrete’s strength and durability, increasing the likelihood of cracking.
  • Lack of Control Joints: Failing to install control or expansion joints at appropriate intervals can result in uncontrolled cracking due to thermal expansion or shrinkage.
  • Poor Formwork Support: Weak or improperly supported formwork can deform under the weight of the concrete, causing uneven settling and cracking.
  • Faulty Pouring Techniques: Pouring concrete too quickly or excessively can trap air and induce surface cracking.
  • Improper Finishing: Incorrect finishing techniques, like overworking the surface or finishing too early, can weaken the concrete and lead to surface cracks.

It is crucial to adhere to proper construction practices, follow industry standards, and engage experienced professionals to minimize the risk of cracking in concrete structures.

Keeping Concrete Structures Strong with Expert Crack Prevention and Repair!

At RyanCo Concrete, we prioritize the longevity and strength of your concrete structures. Our commitment to quality construction practices includes comprehensive crack prevention and repair solutions. 

From proper mix design and reinforcement to expert placement and curing, we ensure your concrete remains resilient and crack-free. In the event of cracks, our skilled team employs advanced repair techniques, using high-quality materials to restore the structural integrity of your concrete. 

Trust RyanCo Concrete to keep your concrete structures strong, durable, and looking their best, ensuring they stand the test of time.