Types of Concrete Cracks: Description, Standards, Identification, and Significance
Plastic Shrinkage Cracks
Description:
These cracks form on the surface of fresh concrete soon after placement, usually while the concrete is still plastic (before it hardens). They are typically shallow, parallel, and can be widely spaced.
Cause:
Rapid loss of water from the surface due to evaporation exceeding the rate of bleed water rising to the surface.
Significance:
Usually affect appearance and durability. In severe cases, they may reduce protection for reinforcement.
Plastic Settlement Cracks
Description:
Vertical cracks that occur while concrete is settling, typically over reinforcing bars or embedded items.
Cause:
Settlement of solids in the mix while the concrete remains plastic, often aggravated by heavy reinforcement or improper vibration.
Significance:
May create channels for water and corrosive agents to reach steel reinforcements, leading to corrosion.
Drying Shrinkage Cracks
Description:
Thin cracks that appear weeks or months after placing concrete as it dries and loses moisture. These cracks are often random or follow a regular pattern (map-cracking).
Cause:
Loss of water from hardened concrete, leading to volume reduction and cracking.
Significance:
May penetrate the entire depth, affecting durability and watertightness.
Thermal Cracks
Description:
Cracks due to temperature variations: can occur during concrete setting (thermal shock) or later due to expansion and contraction.
Cause:
Expansion and contraction from temperature changes, improper curing, or thermal gradients in large elements.
Significance:
Can compromise strength and lead to further structural problems, especially in massive pours.
Structural Cracks (Flexural, Shear, Tension, Compression Cracks)
Description:
Cracks caused by loads exceeding the design capacity of concrete elements. They include:
Flexural Cracks: At mid-spans of beams/slabs, perpendicular to axis.
Shear Cracks: Near supports, at 45° angles.
Tension/Compression Cracks: In member sections subjected to excessive force.
Cause:
Excessive loading, design errors, inadequate reinforcement, or differential settlement.
Significance:
Can severely affect the safety and serviceability of the structure.
Settlement Cracks (Foundation Settlement)
Description:
Wide, irregular cracks often extending through the entire structural element.
Cause:
Differential settlement of foundations due to soil movement or inadequate ground preparation.
Significance:
May indicate serious structural instability.
Corrosion Cracks
Description:
Cracks parallel to the reinforcement.
Cause:
Rusting and expansion of steel bars, leading to cracking and spalling of the concrete cover.
Significance:
Serious concern for durability and structural integrity.
Crazing (Map Cracking)
Description:
Network of very fine, shallow cracks on the surface.
Cause:
Rapid drying or improper curing, usually cosmetic in nature.
Significance:
Generally affects appearance; rarely impacts structural performance.
Standards Related to Concrete Cracking
ACI 224R-01: Causes, Evaluation, and Repair of Cracks in Concrete Structures
EN 1992-1-1 (Eurocode 2): Design of concrete structures – Cracking control
BS 8110: Structural use of concrete
ASTM C856: Standard Practice for Petrographic Examination of Hardened Concrete
Methods for Crack Identification
Visual Inspection:
Most cracks are identified by careful visual survey; measuring width, length, and direction.
Crack Width Gauges:
Tools for precise measurement of surface crack width.
Non-Destructive Tests (NDT):
Ultrasonic pulse velocity, ground penetrating radar, and other devices for internal crack detection.
Dye Penetration and Water Permeability Tests:
Used to trace the depth or continuity of cracks.
Monitoring Devices:
Crack monitors and data loggers for tracking crack movement or propagation over time.
Importance of Crack Identification and Repair
Durability:
Cracks may allow water, chemicals, and gases to enter, accelerating corrosion and reducing the structure’s lifespan.
Safety:
Structural cracks can compromise load-bearing capacity, risking localized or total failure.
Maintenance Costs:
Early identification and repair prevent more extensive and expensive interventions later.
Aesthetics:
Some cracks affect only appearance, but may still require repair in exposed or architectural elements.
Professional Services
RBS-CONTECH (a brand of Iran Concrete Clinic Group) offers engineering, assessment, and specialized repair services for all types of concrete cracks, using advanced equipment and highly qualified expert teams, following international best practices and standards.
For assistance or further information:
www.clinicbeton.com
www.rbs-contech.com
Email: clinicbeton.com@gmail.com
Phone: +982188070173, +982188584906
Mobile: +989102333497, +989120916271, +989120916272