How To Prevent Cracks In Concrete?

Home » Concrete Engineering » How To Prevent Cracks In Concrete?

Concrete cracks are lines on the surface where the material has split without completely breaking apart. Let’s explore why these cracks happen and how they can be prevented.

Factors Leading to Concrete Cracks

Concrete is susceptible to cracking for various reasons, including:

Temperature and Plastic Shrinkage:

  • Shrinkage cracks often appear in large concrete slabs, typically running parallel to the floor’s span.
  • The cracks result from insufficient distribution steel in the concrete, as recommended by the Indian standard code IS: 456 – 2000.
Causes of Shrinkage Cracks Preventive Measures
Very rapid moisture loss Adequate provision of distribution steel
Factors: air temperature, humidity, wind Following IS: 456 – 2000 guidelines for minimum reinforcement

Thermal Changes : Concrete and steel experience differential volume changes due to varying rates of heat loss in different parts of a structure, leading to cracks.

Drying Shrinkage : Moisture loss from cement paste constituents can cause shrinkage up to 1%, resulting in tensile stress and eventual cracking.

Chemical Reaction : Harmful reactions between concrete materials or external substances can lead to cracks and structural deterioration.

Weathering : Weather processes like freezing and thawing, wetting and drying, and temperature fluctuations contribute to crack development.

Poor Construction Practices : Mistakes during construction, such as excessive water in the mix or inadequate formwork support, may cause cracks.

Common Poor Practices Impact on Concrete
Excess water in concrete mix Reduced strength and increased vulnerability
Improper curing Decreased durability and increased cracking
Lack of formwork support Structural instability
Inadequate compaction Reduced strength and increased permeability
Poor placement of construction joints Heightened stress points and potential cracking

Preventing Concrete Cracks

To prevent concrete cracks, consider the following measures:

  • Proper curing with materials like gunny bags to retain moisture.
  • Adequate water addition based on the concrete’s requirements and proper water-cement ratio.
  • Use high-quality materials and adhere to the correct mix design.
  • Ensure proper vibration during concreting.
  • Place concrete from suitable heights (not exceeding 1m) to prevent potential damage.
  • Use shrinkage-reducing admixtures to minimize cracks.
  • Implement control joints in the concrete.
  • Avoid using calcium chloride admixtures in the mix.

Materials for Concrete Crack Repair

Various materials can be used to repair cracks in concrete:

  • Cement slurry
  • Cement mortar
  • Epoxy resins
  • Polymer Modified Cementitious Products (PMCC): Poly Vinyl Acetate (PVAC), Styrene Butadiene Rubber (SBR), Poly Vinyl Diene Dichloride (PVDD), and acrylics.