I've got a footing and stem wall pour in northern Georgia and the forecast is highs in the 40s, lows in the 20s all week.

You must protect the concrete from freezing until it reaches 500 psi (typically 2–3 days at these temps). ACI 306R-16 and IBC 1905.12 require cold-weather procedures when air temp < 40°F.

Changes required for this pour:

1. Order Mix: Specify Type III cement (high-early), accelerator (non-chloride if rebar present), 4–6% air entrainment (mandatory for freeze-thaw durability in GA), and low slump (4" max). Target 4,000 psi min.
2. Prep: Remove all ice/frost from forms, rebar, and subgrade (thaw with heaters if needed). Subgrade must be > 35°F. Do not place on frozen ground.
3. Placement: Place quickly. Target concrete temp 55–60°F leaving plant. If truck temp < 50°F, reject load.
4. Protection (Critical): Corners/Edges: Double insulation (R-10 min). Use insulated blankets over poly vapor barrier. Verticals (Stem Walls): Blanket the outside of forms immediately after strike-off. If stripping forms < 3 days, re-cover immediately. Heat Source: Ground-thaw heaters or hydronic heat under blankets if lows hit 20°F. Maintain concrete temp > 50°F* for 72 hrs (ACI 306 Table 5.1).
5. Curing: Keep blankets on 7 days minimum at these lows. No water curing (freeze risk).
6. Verification: Use maturity meters or field-cured cylinders matching slab conditions to verify 500 psi before removing heat/blankets. Infrared gun checks surface only—useless for core temp.

Do not pour if you cannot maintain 50°F internal temp for 72 hrs. Cost of blankets/heaters << cost of tearing out frozen footings.

For a footing and stem wall pour in northern Georgia with forecasted highs in the 40s°F and lows in the 20s°F, you must implement cold-weather concrete protection per ACI 306R-16 and IBC Section 1904.3 (or local amendments). Below are the required changes:

Critical Adjustments:

1. Concrete Temperature at Placement: - Minimum 55°F (ACI 306R Table 5.1) for sections <12" thick (typical footings/stem walls). - Heat aggregates and/or water; use heated enclosures or insulated blankets if needed. Do not use antifreeze admixtures—they reduce strength and are not permitted for structural concrete per ACI 306.

1. Protection After Placement: - Maintain concrete ≥50°F for at least 48 hours (ACI 306R §5.3) to achieve sufficient strength for freeze-thaw resistance. - Use insulated blankets, heated enclosures, or straw coverings with plastic sheeting to retain heat. - Monitor internal temperature with thermocouples or infrared guns—do not rely on air temp alone.

1. Subgrade Preparation: - Do not place concrete on frozen ground. Thaw and dry subgrade; use insulation or heated forms if freezing is imminent. - Remove ice, snow, or standing water before pour.

1. Curing: - Continue protection for 7 days total (or until 70% design strength is reached) to prevent thermal cracking and ensure hydration. - Avoid rapid cooling—remove insulation gradually over 24–48 hours to prevent thermal shock.

1. Testing: - Cast and cure cylinder specimens under same conditions as structure (ACI 306R §8.2) for accurate strength assessment.

What NOT to Do:

• ❌ Do not pour if ambient temp is falling and cannot be maintained above freezing during placement and initial set.
• ❌ Do not use calcium chloride in reinforced concrete—it promotes corrosion (ACI 318 §26.3.2).
• ❌ Do not finish concrete while bleed water is present—wait for it to dissipate to avoid scaling or delamination.

Recommendation:

If temperatures are consistently below 20°F at night, consider delaying the pour unless you can provide heated enclosures with forced-air heaters (vented to avoid CO₂ buildup) and continuous temperature monitoring. In northern Georgia, such cold snaps are short—waiting 2–3 days for a milder forecast may be safer and more cost-effective than extensive cold-weather protection.

Consult your structural engineer or local building official for project-specific requirements, especially if inspections are scheduled during the cold period. Stay safe—frozen concrete is weak concrete.