Construction / Cold Joint

Construction / Cold Joint

Design Width

6–12 mm

Function

Occurs when concreting stops and restarts

Material

Hydrophilic strip + cementitious waterproofing

Movement

Minor

Typical Application Detail

Rafts, retaining walls

Typical Locations

Retaining walls, terrace slabs, lift pits

Waterproofing Approach

Swellable waterbar + crystalline coating

1. Introduction

Construction or cold joints occur when concreting is interrupted, leading to a discontinuity in bonding between old and new concrete.

They are prime leakage zones in rafts, retaining walls, and water tanks.

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2. Typical Failures

  • No waterbar installed during casting.
  • Poor surface preparation before next pour.
  • Honeycombs or laitance at the interface.
  • Absence of crystalline or epoxy bonding layer.

3. System Requirements

  • Provide watertight bond between pours.
  • Use hydrophilic waterbars to seal leakage paths.
  • Reinforce with crystalline coatings or PU sealants where required.

4. Recommended Systems

Joint Type
System
Materials
Raft–wall junction
Swellable waterbar + crystalline slurry
Hydrophilic strip + cementitious membrane
Wall–column
Hydrophilic cord + epoxy bonding agent
PU sealant / Epoxy mortar

5. Methodology

  1. Clean laitance and debris.
  2. Apply crystalline coating or bonding agent on old concrete.
  3. Fix swellable waterbar along the joint line.
  4. Pour new concrete ensuring full compaction.
  5. Protect joint with cementitious waterproofing.

6. Performance Parameters

Property
Requirement
Standard
Water tightness
No leakage @ 5 bar
ASTM D5385
Swelling ratio
300–400%
ASTM D471
Adhesion
≥1.0 N/mm
ASTM C794

7. QA/QC Checklist

  • ☑ Waterbar correctly centered
  • ☑ Joints cleaned and slurry applied
  • ☑ Pour completed in continuous sequence
  • ☑ Curing monitored

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Disclaimer

SpecX is an industry initiative & a neutral resource, compiled from industry references and best practices. It is not brand-specific. Always cross-check with project requirements and local codes before finalizing specifications.