In structures for which rebar corrosion isn't an issue, calcium chloride is the most economical and effective accelerating admixture. It's widely used in a liquid solution in unreinforced pavements, residential foundation walls, and floors placed in cold weather. It helps concrete set and gain strength faster, allowing finishers to complete their work sooner and decreasing the likelihood of damage caused by early freezing.
Because large doses can cause undesirably fast setting and may reduce strength at later ages, the recommended maximum dosage is 2 pounds of commercial calcium chloride per 100 pounds of cement. But in cold weather, contractors sometimes double the recommended dosage unless specifications prohibit this practice. Are cold-weather dosages greater than 2% helpful, harmful, or ineffective?