Concrete is one of the most reliable materials in modern construction, valued for its strength, durability, and versatility. However, even the best-designed concrete structures can develop cracks over time. These cracks are not always a sign of failure but rather indicators of stress, environmental effects, or construction practices. Understanding the types of cracks in concrete and their causes is crucial for engineers, contractors, and property owners to maintain structural integrity and safety.
At MFS Engineers & Surveyors, our structural engineering team specializes in assessing and addressing concrete issues to ensure long-lasting, reliable structures. In this blog, we’ll explore the most common types of concrete cracks, why they occur, and how they can be addressed.
Plastic Shrinkage Cracks
Plastic shrinkage cracks often appear when concrete is still in its plastic state, before it has hardened. These cracks are usually shallow and irregular, resembling a web-like pattern on the surface. They occur when moisture evaporates too quickly from the surface due to environmental factors like high temperatures, low humidity, or strong winds. Excess water in the concrete mix can exacerbate the problem. To prevent plastic shrinkage cracks, contractors can use methods like misting water over the surface or employing windbreaks to reduce rapid evaporation.
Settlement Cracks
Settlement cracks form when the ground beneath the concrete shifts or compacts unevenly. These cracks, which often run vertically or diagonally, can extend through the entire depth of the concrete, posing potential structural risks. Poorly compacted subgrade or heavy loads placed on freshly poured concrete are common causes of settlement cracks. Proper site preparation and subgrade compaction are essential to minimize the risk. For existing cracks, stabilization techniques such as underpinning or grouting can effectively restore integrity.
Thermal Cracks
Thermal cracks develop when temperature fluctuations cause the concrete to expand or contract. These cracks are particularly common in large concrete structures, where internal temperature differences can create tensile stresses. Seasonal changes, extreme heat, or freezing temperatures can also contribute to their formation. Incorporating expansion joints in the design and using concrete with low thermal expansion properties are effective strategies for mitigating thermal cracks.
Structural Cracks
Structural cracks are among the most serious types of cracks in concrete. These cracks typically appear near load-bearing elements such as columns, beams, or foundations and may compromise the structure’s stability. Causes include overloading, poor structural design, or differential settlement. Structural cracks often require immediate attention from a structural engineer to assess the damage and recommend solutions. Reinforcement techniques, such as adding steel reinforcements or using carbon fiber wraps, can help restore the structural integrity.
Splitting Cracks
Splitting cracks, also known as splitting tensile cracks, typically occur due to tensile forces acting perpendicular to the length of the concrete. These cracks often run along the length of the concrete element and are common in cylindrical or elongated members, such as columns and pipes. Splitting cracks can be caused by improper load distribution, freezing and thawing cycles, or excessive moisture content leading to internal pressure.
Preventing splitting cracks requires careful attention during the design and construction phases. Engineers must ensure proper reinforcement placement, adequate concrete strength, and measures to protect against environmental stressors. For existing cracks, repair methods may include grouting or applying external reinforcements to restore the element's structural integrity.
Corrosion Cracks
Corrosion cracks occur when steel reinforcement within the concrete begins to corrode. This type of crack is particularly concerning because it not only affects the concrete's durability but also signals potential structural vulnerabilities. Corrosion of embedded steel is often caused by exposure to moisture, chlorides, or carbon dioxide, which creates an electrochemical reaction that expands the steel. This expansion exerts pressure on the surrounding concrete, leading to cracking and spalling.
To mitigate corrosion cracks, it’s crucial to use protective measures such as high-quality concrete with low permeability, proper coverage of reinforcement, and the application of corrosion-resistant coatings or cathodic protection systems. Addressing existing corrosion cracks requires professional evaluation to ensure both the steel and concrete are adequately repaired, often involving techniques like epoxy injection or replacing damaged reinforcement.
Diagonal Cracks in Foundations
Diagonal cracks in concrete foundations are often caused by uneven settlement or soil movement. These cracks typically run at an angle of 30 to 45 degrees and can widen over time, posing significant risks to structural stability. Expansive soils or poor drainage around the foundation are common culprits. Solutions include improving drainage to prevent water accumulation and stabilizing the soil using techniques like chemical injections or Piering systems.
Overload Cracks
Overload cracks result from excessive stress or weight placed on a concrete structure. These cracks can appear anywhere and are often jagged and wide. Improper load distribution or unforeseen heavy loads are typical causes. Consulting a structural engineer during the design phase ensures the structure is built to withstand the intended loads, reducing the likelihood of overload cracks.
Why Cracks Matter
While some cracks are purely cosmetic, others can compromise a structure’s safety and longevity. Early identification and intervention are critical to prevent minor cracks from developing into costly problems. Regular inspections and maintenance are essential for preserving the integrity of concrete structures.
How MFS Engineers & Surveyors Can Help
At MFS Engineers & Surveyors, we provide expert structural engineering services to evaluate and address concrete issues. Whether it’s assessing minor surface cracks or diagnosing deeper structural concerns, our team delivers tailored solutions that ensure safety and durability. From structural assessments and crack repair designs to foundation stabilization and reinforcement retrofitting, we’re equipped to handle even the most complex challenges.
Contact us today to discuss your needs or schedule a consultation with our structural engineering team. Together, we’ll build structures that stand the test of time.