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- 2078 Chaitra · 4 marks
- 2077 Chaitra · 4 marks
Causes and remedies of cracks
Short answer
Causes: moisture and thermal movement, foundation settlement, elastic deformation, reinforcement corrosion, chemical attack, vegetation, earthquake, poor work, overloading, fire. Remedial measures: hairline – cement slurry; small – rake and fill with 1:3 mortar; medium – epoxy injection; wide – stitching, jacketing or rebuild; settlement – underpinning; provide movement joints and good curing.
Write down the causes of cracks that occur in a building and its remedial measures briefly.
Cracks in buildings arise from the following causes.
| Cause | How it cracks the building |
|---|---|
| Moisture movement | Bricks, blocks and concrete expand on wetting and shrink on drying; mortar and plaster shrinkage |
| Thermal movement | Expansion and contraction with temperature in roofs, long walls, parapets |
| Settlement of foundation | Unequal settlement due to poor or non-uniform soil, wrong foundation level, change in moisture, or inadequate depth |
| Elastic deformation | Overload, deflection of beams and slabs, bending and shear |
| Corrosion of reinforcement | Rust expands and splits the concrete cover |
| Chemical action | Sulphate attack, alkali-aggregate reaction, carbonation |
| Vegetation | Roots of trees near walls and foundations |
| Earthquake and wind | Lateral forces on weak walls and joints |
| Poor workmanship and materials | Poor curing, mix, bonding, early removal of formwork, missing joints |
| Overloading and design error | Excess load, wrong detailing |
| Fire, vibration | Heat damage, machine vibration |
Remedial measures
| Crack width | Remedy |
|---|---|
| Hairline (< 0.3 mm) | Fill with cement slurry or paint-grade filler; fresh plaster |
| Small (0.3-1.0 mm) | Rake out, fill with cement-sand mortar (1:3) or polymer-modified mortar |
| Medium (1-3 mm) | Epoxy injection or cement grout through packers |
| Wide (> 3 mm) | Remove and rebuild, stitching with steel clamps, epoxy mortar, jacketing |
| Foundation settlement | Underpinning, grouting, soil improvement |
| RCC cracks | Epoxy injection, grouting, jacketing, bonding steel plates |
| Roof cracks | Waterproof treatment, expansion joints, sealants |
Additional measures: provide movement joints, good drainage, proper curing, tie beams, and good-quality materials.
✓ Answer checked by Claude Opus 5.5 (high effort)
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