What precautions are needed for cold weather concreting?

Cold weather concreting (below 5C) precautions include: heating mixing water and aggregates, using Type III (high-early) cement or accelerators, increasing cement content, protecting fresh concrete with insulation and enclosures, maintaining minimum concrete temperature (10-15C), extending curing period, and never placing on frozen surfaces. Critical period is until concrete reaches 5 MPa. Freeze-thaw damage before strength gain causes permanent damage. Monitor temperature with embedded thermocouples.