Executive Summary
This case study details how calcium chloride (CaCl₂) was successfully employed as a concrete accelerating admixture to enable a critical winter foundation pour. Facing sub-freezing temperatures, the project team integrated a calcium chloride-based admixture into the concrete mix. This intervention accelerated early strength development by 60%, prevented frost damage, and eliminated the need for costly heated enclosures. The project was completed on schedule, demonstrating calcium chloride's effectiveness as a reliable and economical solution for cold-weather concreting.

Background & Challenge
The construction schedule for the Great Lakes Logistics Terminal required the main warehouse foundation—a reinforced concrete slab—to be completed before late December to allow for steel erection in January. A supply chain delay pushed the pour to late November, introducing significant cold-weather risks. Concrete hydrates slowly below 40°F (4°C), and if pore water freezes before reaching about 500 psi compressive strength, permanent damage from internal ice expansion occurs. Traditional methods like heated enclosures were prohibitively expensive and logistically complex for this scale.

The Solution: Calcium Chloride Integration
The team specified a concrete mix with a liquid accelerating admixture compliant with ASTM C494, primarily based on calcium chloride.

Technical Rationale: Calcium chloride acts as a catalyst, accelerating the cement hydration reaction. This generates internal heat, promotes rapid early strength gain, and slightly depresses the freezing point of the mix water.
Implementation: The ready-mix supplier dosed trucks with the admixture at approximately 2% by weight of cement. Complementary measures included using slightly heated mixing water and covering the slab with insulated blankets after pouring.

Execution & Monitoring
The pour proceeded over two days. Crews adjusted to a faster initial set time. Embedded temperature sensors confirmed the concrete stayed above 45°F (7°C) due to the exothermic reaction. Strength tests on field-cured cylinders confirmed the concrete exceeded the critical 500 psi threshold within 20 hours, well before the first deep freeze.

Results & Benefits
Performance: Early strength gain was 60% faster than a standard mix under identical conditions. No frost damage occurred. Final 28-day strength exceeded design specs.
Cost Savings:Eliminating the need for temporary heaters, fuel, and enclosure monitoring saved an estimated $92,000**.
Schedule Adherence: The foundation was ready for the next trade on time. Avoiding a two-week delay prevented an estimated $225,000 in potential liquidated damages and extended costs.

Indirect Benefits:Reduced the project's temporary carbon footprint by avoiding constant fossil-fuel heating.

Conclusion
The successful use of calcium chloride transformed a weather-related risk into a controlled, efficient operation. This case reaffirms that calcium chloride, when applied according to best practices, remains a highly effective, predictable, and cost-efficient admixture for ensuring structural integrity and schedule adherence in cold-weather construction. It highlights the value of integrating proven chemical solutions with proactive project planning to overcome environmental challenges.