Curing Concrete in Cold Weather
Curing concrete in cold weather areas is very difficult to complete. Snow, humidity and water will prevent your concrete to settle down. Concrete hydration is affected when temperature drops below zero degrees or freezing point. It is essential that the concrete is places on a clean surface without snow or other materials that could affect the curing of the concrete. It is highly recommended to use heat preserving techniques resulting in better curing, setting and finishing’s. American Concrete Institute (ACI) Committee 301 recommends a minimum curing period corresponding to concrete attaining 70% of the specified compressive strength
Curing Concrete Cold Weather Materials
Curing concrete in cold weather can be achieved using different materials depending on the amount of concrete being cured and the surface being protected. These materials when used properly will increase or produce a constant heat of hydration of the concrete. For example:
- Insulating sheets,
- Heating coils,
- Insulating blankets, and
However, if the temperature is below 20 Degree F, simply skip the idea of placing concrete because it will lead you nowhere as hydration stops completely at such temperatures.
For this reason, ACI Committee 308 recommends the following minimum curing periods:
- ASTM C 150 Type I cement 7 days
- ASTM C 150 Type II cement 10 days
- ASTM C 150 Type III cement 3 days
- ASTM C 150 Type IV or V cement 14 days
- ASTM C 595, C 845, C 1157 cements variable
Curing Concrete in Cold Weather Tips
Try these recommended tips for curing concrete in cold weather:
- Maintain a proper water-cement ratio. The water to cement ratio should not be more than 0.40 under freezing conditions.
- If temperatures are too cold, a propane heater and polyethylene enclosure could be used to maintain temperatures hot enough, to avoid freezing point.
- Use Portland cement Type III, cement that helps in setting without reducing concrete’s quality. It is important because high moisture content can induce corrosion problems in steel reinforcement.
- Control chloride ions by suing fly ash, silica fume and furnace slag.
- Leave forms in place as long as possible. Corners and edges are most vulnerable.
- Removing the blankets suddenly in cold weather can cause a temperature differential to build up between the outside of the concrete and its middle. This can cause cracking from the thermal differential, but typically only in thicker members.
- Concrete under water curing for flatwork applications becomes easy with previous concrete. Pervious Concrete is all coarse aggregates and it contains a negligible percentage of fine aggregates, especially sand. Additives are mixed into it that do not allow water to penetrate inside the concrete surface. Pervious concrete is suitable for constructing pavement as it does not soak in water but allows gallons of water pass through it without damaging concrete pavement and strength.
- Wait until all bleed water has evaporated. Curing concrete in cold weather will produce a slower curing procedure, so the concrete is setting slowly, and bleeding will also start later than expected. Be prepared to handle more bleed water than regular concrete placement.
- While concrete is being cures, verify the concrete temperature using an infrared temperature gun.
- To determine how much insulating value you need to keep the concrete at 50°F, check out the tables in Chapter 7 of ACI 306. The insulation needed is based on concrete thickness, cement content, and the lowest air temperature anticipated for the protection period.
- Seal concrete by applying concrete sealant so water does not seep inside the concrete. Concrete sealants will extend concrete’s life, and will reduce the concrete curing failure. In extremely cold regions, only a breathable concrete sealant must be used, as it will allow the evaporation of water and moisture, helping in fast setting of the concrete.