Why does concrete crack in cold weather
Cold weather concrete can be classified as a period longer than three days during which certain conditions occur at certain temperatures. The American Concrete Institute under ACI 306 defines that concrete is exposed to cold weather when the following conditions are met:
- The average daily air temperature is less than 5 ° C (40 ° F) and
- The air temperature will not exceed 10ºC (50ºF) for more than half of a 24 hour period.
If the concrete is farmed in cold weather, it must be protected from freezing shortly after it has been poured. Concrete must also be able to develop the strength required for safe removal from molds while reducing the circumstances in which excessive heat must be applied to help the concrete develop the required strength. Other important factors to consider are the appropriate curing conditions that will prevent cracking and provide the intended maintainability of the structure.
Cold Weather Concrete Recommended Tips
Follow these recommended steps to ensure that concrete is the required structural strength in cold weather and that you are tightening it; There are no other problems while the concrete is being set.
- Before filling out, define the strategies that will be used including materials, forms, tests, and other requirements.
- Plan and determine the cold weather protection measurement of the concrete mix.
- Maintain a well-defined temperature recording table including the concrete temperature and the outside temperature.
- Never pour concrete over frozen ground, snow or ice. Use heating equipment to thaw the floor before pouring concrete.
- Determine if specific considerations and strength requirements need to be met; If so, protect the concrete at certain temperatures.
- If heated enclosures are used when laying concrete in cold weather, you need to know that they must be wind and weatherproof.
- If combustion heaters are used, vent the air to the outside to prevent carbonation.
- Cold weather concrete should have the right amount of air pores to withstand the effects of freezing and thawing.
- Cold weather concrete is recommended to have a low break-in and a minimal water-to-cement ratio to reduce bleeding and shorten setting time.
- Use concrete plaster ceilings to prevent freezing and keep the concrete at an optimal setting temperature.
- Use insulating blankets or heated enclosures to maintain concrete temperatures above 50 degrees Fahrenheit for three to seven days.
- Do not start the final completion while there is blood.
- Request a heated mix or order 100 pounds. of additional cement for every cubic yard of concrete. This extra cement helps develop an early strength.
- Fresh concrete frozen in the first 24 hours can lose 50% of its potential 28 day strength!
- Keep the concrete temperature above 40 degrees Fahrenheit for at least an additional four days after using the insulating blankets or heated enclosures.
- Be careful! ! The concrete temperature cannot drop faster than more than 40 degrees Fahrenheit in 24 hours.
- If there's no other option, adding a cement bag to the mix will help.
- Do not seal freshly placed concrete until it is bleeding and the setting process has started.
- It is recommended to start laying concrete as soon as possible. If the batch plant is too far from the final destination of the concrete, additional steps must be taken to reduce the adjustment problems.
- Water heaters may not be able to withstand higher temperatures after the first few batches.
How to maintain concrete temperatures in cold weather
The temperatures for placing and protecting concrete in cold weather are specified and prescribed under ACI 306. The aim of the ACI 306 is to keep the concrete warm above 5 degrees Celsius. the first 48 hours when concrete strength is critical.
If concrete is set below 5 degrees but not below freezing, it will take longer for concrete to achieve the required strength. Note that removing the formwork if the concrete is too cold or has not achieved the desired strength could damage the concrete strength and surfaces, and concrete could collapse.
Frost protection cloths and insulated formwork may be required to protect concrete. Insulated shapes or temporary coverings could provide adequate insulation in beams, pillars and walls.
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