How I can Identify Cracks by Appearance?

What are the causes ?




We have seen cracks in different formats, some are straight lines, diagonal, web, zig-zag lines etc. These cracks can be identified through their shape, location and sizes. Following are the shapes of cracks which helps to find out the reasons, and further their solutions in a table.






Identification of Cracks on Concrete Surface

From the image, it is easy to remember all these above types of cracks. Below image can help the civil engineers to identify the cracks at their site or project.

The Alphabet written on the each crack can be correlate with below table which clarify the MOST COMMON LOCATION, PRIMARY & SECONDARY CAUSE, and REMEDY as well. These are intrinsic cracks. For further details, please refer links mentioned on the side bar.









Cause, Remedy & Time of Appearance of Crack





Cracks can be found in two situations:

A) Cracks - Before Hardening

1. Plastic
    a) Plastic Shrinkage
    b) Plastic Settlement

2. Constructional Movement
    a) Form work Movement
    b) Sub-Grade Movement

3. Early Frost Damage





B) Cracks After Hardening


1. Physical
    a) Shrinkable Aggregates
    b) Drying Shrinkage
    c) Crazing
2. Chemical
    a) Corrosion of Reinforcement
    b) Alkali-Aggregate Reactions
    c) Cement Carbonation
3. Thermal
     a) Freeze/Thaw Cycles
     b) External Seasonal Tmpratures Variations
     c) Early Thermal Contractions
         i) External resistant
        ii) Internal temprature gradients
4. Structural
    a) Accidental Overload
    b) Creep
    c) Design Loads





Conclusion

  • Engineers must have sound knowledge of crack formation time, reason, knowledge, and remedies to remove the cracks from the surface.
  • Paying attention at every step of making and supervision of concrete are also playing a vital role of minimizing the cracks on structure.
  • Broad idea about the weather before concreting, during concreting, and after concreting will help to avoid cracks formation.
  • There are other factors apart from above like leveling of shuttering, cover to reinforcement, slump of concrete etc which have to be considered while planning the concrete.







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