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.
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
- Clean laitance and debris.
- Apply crystalline coating or bonding agent on old concrete.
- Fix swellable waterbar along the joint line.
- Pour new concrete ensuring full compaction.
- 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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