| Parameter | Requirement |
|---|---|
| Cold weather defined | Air <5°C or expected <5°C within 24 hrs |
| Concrete temp at placement | Min 10°C thin (<300 mm); 5°C mass |
| Protection period | Maintain >10°C until 7 MPa reached |
| Gradual cooling rate | Max 1°C/hour (thin sections) |
| Monitoring frequency | Every 4 hrs (first 72 hrs), then 8 hrs |
| Hot water from plant | 60–80°C (never >80°C) |
| Type HE cement | 7 MPa in 24–36 hrs vs. 48–72 hrs (GU) |
| Air entrainment C-2 / C-1 | 5–8% / 4–7% |
| Max w/c ratio | 0.40–0.45 (cold weather) |
Reject ANY load below 10°C (thin) or 5°C (mass). No exceptions.
| Parameter | Requirement |
|---|---|
| Mortar temp at placement | Min 15°C |
| Masonry unit temp | Above 0°C; no saturated frozen units |
| Protection period | 24 hrs min — mortar must not freeze |
| Wind protection | Required >25 km/h & <5°C |
| Mortar board max time | 30 min; discard if <10°C |
| Mix water temp | 50–70°C (add to sand first) |
| Antifreeze admixtures | NOT endorsed for structural masonry |
| Grout in CMU cells | Pre-heat wall 12 hrs before grouting |
Frozen mortar = zero bond strength. Wall collapse at first thaw.
| Heater Type | Output | Key Rule |
|---|---|---|
| Indirect-fired | 100–1,000 MBH | Default — no CO inside |
| Direct-fired | 75–400 MBH | Large ventilated only + CO monitor |
| Hydronic (glycol) | 200–1,500 MBH | Under-slab, perimeter, thawing |
| Electric forced air | 15–150 kW | Zero CO; small enclosures |
| Level | Action |
|---|---|
| 25 ppm (OEL TWA) | Increase ventilation; fix source; evacuate if not <25 in 15 min |
| 50 ppm | Evacuate immediately; re-enter only <10 ppm |
| 200 ppm | Disorientation in 2 hrs |
| 800 ppm | Unconsciousness in minutes |
| Temperature | Protocol |
|---|---|
| Below −10°C | 10-min warm-up break every hour |
| Below −20°C | 15-min warm-up every 45 min |
| Below −25°C wind chill | Suspend outdoor work (unless heated enclosure) |