Temperature limits and precautions for placing concrete in extreme weather. Covers maximum and minimum concrete temperatures at the time of placing, ambient temperature thresholds, and mandatory precautions for hot and cold weather concreting.
Hot Weather Concreting (IS 7861-1)
Applicable when ambient temperature exceeds 40°C or concrete temperature at placing exceeds 30°C
| Condition | Limit | Action Required | Clause |
|---|
| Maximum concrete temperature at placing | 40°C (absolute maximum) | Do not place if concrete exceeds 40°C | IS 7861-1 Cl. 5.1 |
| Preferred concrete temperature at placing | ≤ 30°C | Use chilled water, ice, or cooled aggregates to bring temperature down | IS 7861-1 Cl. 5.1 |
| Ambient temperature > 40°C | Avoid concreting | Schedule pours during early morning or night; provide shade over batching & placing areas | IS 7861-1 Cl. 4.2 |
| High wind speed (> 25 km/h) | Increased evaporation risk | Erect wind screens around pour area; apply evaporation retarder on surface | IS 7861-1 Cl. 4.3 |
| Low relative humidity (< 40%) | High evaporation rate | Fog spray the area; begin curing immediately after finishing | IS 7861-1 Cl. 4.3 |
| Use of ice in mixing water | Ice must be fully melted before concrete leaves mixer | Add flake ice or crushed ice to mixing water; verify no ice lumps in discharged concrete | IS 7861-1 Cl. 6.2 |
| Transport time in hot weather | ≤ 30 minutes from batching to placing | Minimise transit time; cover transit mixer drum with wet hessian if needed | IS 7861-1 Cl. 6.3 |
| Curing in hot weather | Start within 30 minutes of finishing | Ponding, wet hessian, or curing compound; maintain for minimum 14 days | IS 7861-1 Cl. 7 |
| Use of retarding admixture | As per IS 9103 | Add retarder to extend setting time by 1–2 hours; adjust dosage for ambient temperature | IS 7861-1 Cl. 6.4 |
Cold Weather Concreting (IS 7861-2)
Applicable when ambient temperature falls below 5°C or is expected to fall below 0°C within 24 hours
| Condition | Limit | Action Required | Clause |
|---|
| Minimum concrete temperature at placing | 5°C | Do not place concrete if its temperature is below 5°C at the point of placement | IS 7861-2 Cl. 5.1 |
| Preferred concrete temperature at placing | 10°C to 25°C | Heat mixing water (up to 60°C) or aggregates to achieve target temperature | IS 7861-2 Cl. 5.2 |
| Ambient temperature falling below 0°C | Freezing risk — concrete must not freeze within first 24 hours | Provide insulating blankets, heated enclosures, or tarpaulins over fresh concrete | IS 7861-2 Cl. 6.1 |
| Heating mixing water | Max 60°C for water; aggregates max 40°C | Heat water first, then add aggregates, then cement — never add cement to hot water directly | IS 7861-2 Cl. 6.2 |
| Formwork removal in cold weather | Delay stripping until concrete reaches 10 MPa minimum | Test maturity before stripping; use insulated formwork to retain heat | IS 7861-2 Cl. 7.2 |
| Use of accelerating admixture | As per IS 9103; calcium chloride ≤ 2% by weight of cement | Add accelerator to speed hydration; avoid calcium chloride in reinforced concrete | IS 7861-2 Cl. 6.3 |
| Curing in cold weather | Maintain concrete above 10°C for minimum 72 hours | Use curing blankets, heated enclosures, or steam curing; protect from freezing for 7 days | IS 7861-2 Cl. 7.1 |
General Temperature Limits
Summary of absolute temperature limits for concrete at the time of placing
| Condition | Limit | Action Required | Clause |
|---|
| Normal weather placing temperature | 15°C to 30°C | No special precautions needed beyond standard practice | IS 456 Cl. 13.1 |
| Absolute maximum at placing | 40°C | Reject if exceeded — cool concrete before placing | IS 7861-1 Cl. 5.1 |
| Absolute minimum at placing | 5°C | Reject if below — heat ingredients before mixing | IS 7861-2 Cl. 5.1 |
| Temperature differential in mass concrete | ≤ 20°C between core and surface | Use low-heat cement, pipe cooling, or pour in smaller lifts | IS 456 Cl. 13.6 |
| Evaporation rate threshold | > 1.0 kg/m²/hr | Take precautions against plastic shrinkage cracking — fog spray, wind screens, evaporation retarder | IS 7861-1 Cl. 4.3 |
Notes
• Use the evaporation rate calculator (ACI 308 nomograph) combining ambient temperature, concrete temperature, relative humidity, and wind speed to decide precautions.
• Retarding admixtures (IS 9103 Type B) are strongly recommended when placing in temperatures above 35°C to maintain workability.
• In cold weather, never use antifreeze compounds as a substitute for proper temperature maintenance — they are unreliable and not permitted by IS codes.
• Mass concrete (sections > 1 m thick) requires separate thermal control planning regardless of ambient temperature.
• All temperature readings should be taken at the point of discharge into formwork, not at the batching plant.
• Maintain temperature logs for every pour as part of the quality control records.
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