| Defect | Cause | Remedy | Severity | Note |
|---|---|---|---|---|
| Honeycombing | Poor compaction, thick concrete with little vibration, congested reinforcement, low slump | Surface honeycomb: chip out + cement slurry + non-shrink grout. Deep: hack to sound concrete, structural epoxy injection. | Moderate to severe | Inspect with chisel — depth determines remedy |
| Bleeding (water on top) | Excess water, lean mix, over-vibration, poor sand grading | Wait for bleed water to evaporate before finishing. If excessive, redo finish coat. | Cosmetic | Causes weak top layer — abrasion-prone |
| Aggregate segregation (rocky bottom) | Dropping concrete from height, excess slump, harsh mix | Hack and recast severe areas. For minor, surface treatment with polymer mortar. | Moderate | Common in column pours from height |
| Sand streaking | Bleed channels, formwork leaks, harsh mix | Plug formwork joints. Surface grouting after striking. | Cosmetic | Visible vertical streaks |
| Defect | Cause | Remedy | Severity | Note |
|---|---|---|---|---|
| Plastic shrinkage cracks | Rapid drying — high temp, low humidity, wind. Water evaporates faster than bleed water rises | Re-trowel within 1 hour. Fog-spray. Cover with wet hessian. For wide cracks, fill with epoxy. | Cosmetic to moderate | Map-pattern, parallel surface cracks. Common on slab tops in summer |
| Plastic settlement cracks | Concrete settles around reinforcement; bars block downward movement creating cracks above | Re-vibration before initial set. After hardening: epoxy inject if wide. | Moderate | Cracks follow top reinforcement pattern |
| Crazing (map cracking) | Rapid surface drying or over-trowelling, fines bleed to surface | Cosmetic only — apply curing compound, dust hardener, or finish coat | Cosmetic | Fine, hexagonal pattern. No structural impact |
| Defect | Cause | Remedy | Severity | Note |
|---|---|---|---|---|
| Drying shrinkage cracks | Concrete loses moisture, contracts. Restrained by reinforcement or substrate | If width < 0.3 mm: cosmetic only. If wider: epoxy injection or polymer-modified grouting. | Cosmetic to moderate | Appear weeks/months after pour. Random direction |
| Thermal cracks (early age) | Heat of hydration in thick pours, poor cooling, restraint | Epoxy injection. For mass concrete, prevent with cooling pipes/ ice. | Moderate | Common in raft and mass pours |
| Flexural cracks (structural) | Bottom of beam in tension — design flaw or overload | Investigate before repair. May need strengthening (FRP wrap, jacket, additional reinforcement) | Severe | Vertical cracks, bottom of beam, max at midspan |
| Shear cracks (structural) | Diagonal tension exceeded, insufficient shear steel | Investigate URGENTLY. External steel, FRP, or jacketing typically required | Severe — danger | Diagonal cracks, near supports, ~45° angle |
| Settlement cracks (foundation) | Differential settlement of foundation | Stabilize foundation FIRST (underpinning, micropiles), then repair cracks | Severe | Diagonal, often through walls; widens over time |
| Corrosion-induced cracks | Reinforcement rusts, expands ~6×, splits cover | Hack cover, clean rebar to bright metal, apply rust converter, repair with polymer mortar. Investigate cover/concrete quality. | Severe | Cracks parallel to reinforcement; rust stains visible |
| Defect | Cause | Remedy | Severity | Note |
|---|---|---|---|---|
| Form streaks / form lines | Form joints not sealed, plywood seams, bleed water tracks | Cosmetic — grind, fill, paint | Cosmetic | Visible after stripping |
| Blow holes (bug holes) | Air trapped against form, no release agent, poor vibration | Fill with cement-water slurry. For architectural, use fairing coat | Cosmetic | Round pinholes, common on column faces |
| Scaling / spalling | Freeze-thaw, surface weakness, abrasion, deicer salts | Hack to sound concrete, re-cover with bonding agent + repair mortar | Moderate | Surface peeling; rare in plains India, common in hills |
| Efflorescence (white deposits) | Soluble salts migrate to surface as moisture evaporates | Brush off, then waterproof source. Acid wash for stubborn deposits. | Cosmetic | White powder on surface; indicates moisture path |
| Discolouration | Different cement batches, calcium chloride, unequal curing | Cosmetic — uniform paint or stain | Cosmetic | Not a structural concern |
| Defect | Cause | Remedy | Severity | Note |
|---|---|---|---|---|
| Mild exposure | — | ≤ 0.3 mm | Acceptable | Internal members, dry environment |
| Moderate exposure | — | ≤ 0.2 mm | Acceptable | External, sheltered |
| Severe exposure | — | ≤ 0.1 mm | Acceptable | Coastal, exposed to rain |
| Very severe / extreme | — | ≤ 0.1 mm | Acceptable | Tidal, chemical attack |
| Liquid retaining (IS 3370) | — | ≤ 0.2 mm | Acceptable | Water tanks; tighter limit applies |
| Defect | Cause | Remedy | Severity | Note |
|---|---|---|---|---|
| Crack < 0.3 mm (cosmetic) | — | Epoxy paint, surface seal | — | No injection needed |
| Crack 0.3–1.0 mm | — | Low-viscosity epoxy injection | — | Pressure inject from one face |
| Crack > 1.0 mm | — | Cement grout / polymer cement | — | Epoxy for structural, cement for non-structural |
| Honeycomb (surface) | — | Hack + bonding agent + non-shrink grout | — | Sika MonoTop or equivalent |
| Honeycomb (deep) | — | Drill + epoxy injection (PCC method) | — | Pressure inject 1–4 bar |
| Spalled cover (corrosion) | — | Hack + clean rebar + polymer mortar repair | — | Apply zinc-rich primer to bars first |
| Structural strengthening | — | FRP wrap / steel jacketing / RCC jacketing | — | Always with engineer approval |