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What damage does the low temperature in winter do to the concrete structure?

For the concrete serving in the freezing and thawing environment and in contact with deicing salt or other corrosive chemical substances, air must be introduced. Sometimes in order to improve the workability of concrete, air must also be introduced.

The air content in concrete can be increased by using air-entrained Portland cement or air-entraining agent. The amount of air-entraining agent is affected by the composition of concrete and working conditions and needs to be adjusted at any time.
It should be noted that the amount of air entraining required to obtain satisfactory resistance to freeze-thaw damage is related to the maximum particle size of the aggregate and the service environment. In the concrete mix ratio, if the maximum aggregate particle size increases, the amount of cementitious material will be reduced, and the demand for air-entraining will also be reduced accordingly.

Under good service environment conditions, such as indoor or outdoor environment without freezing and thawing cycles and deicing salt, from the perspective of durability, there is no special requirement for air-entraining capacity. However, if considering the workability and cohesion of concrete, a small amount of air can be entrained.

Under the mild conditions of the service environment, the concrete structure is in a freeze-thaw cycle environment, but before the ambient temperature drops below the freezing point, it will not be in contact with a humid or water environment for a long time, nor will it be in contact with deicing salts or other corrosive chemicals. Material contact, such as outdoor beams, columns, walls, box beams, or structures that are not in direct contact with moist soil, etc., should adjust the air entrainment volume according to engineering requirements and the composition of concrete.

When the service environment is very harsh, such as long-term contact with deicing salt or other corrosive chemicals, or long-term high saturation before freezing, or long-term contact with water, such as outdoor ground, bridge decks, curbs, and sidewalks , The lining of water channels, pools or sewage tanks and other structures must appropriately increase the amount of air entrained.

When the amount of mixing water remains constant, the increase in air entrainment will increase the slump. When the amount of cement material and slump remain constant, the increase in air entrainment will reduce the amount of mixing water, especially when the amount of cement in the mix is ​​less, this effect is more obvious.
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Post time: Dec-08-2020