What is the primary reason for using insulation blankets as a curing method in cold weather concreting?

The primary reason for using insulation blankets as a curing method in cold weather concreting is to maintain an adequate concrete temperature, preventing freezing and ensuring proper hydration. Hydration is the chemical reaction between cement and water that leads to the hardening and strength development of concrete. At low temperatures, the rate of hydration slows down significantly, and if the concrete freezes before it gains sufficient strength (typically around 500 psi), the water within the concrete expands, causing significant damage to the microstructure and resulting in reduced strength and durability. Insulation blankets act as a thermal barrier, reducing heat loss from the concrete to the surrounding environment. This helps to keep the concrete warm enough to continue hydrating and developing strength, even when the air temperature is below freezing. For instance, placing insulation blankets over freshly placed concrete slabs in winter can prevent the concrete from freezing and allow it to reach its design strength. In very cold conditions, supplemental heating may also be necessary in addition to insulation to maintain the required concrete temperature. Therefore, insulation blankets are a critical tool for ensuring successful concrete placement and curing in cold weather.