Contents of this article
What are the antifreeze measures for concrete?
How to prevent concrete from freezing?
What should be added to concrete to prevent freezing?
What antifreeze measures are needed for concrete?
What measures should be taken to prevent freezing after concrete construction?
What are the concrete anti-freeze specification requirements?
How to prevent freezing and heat preservation of concrete in winter?
How to maintain concrete in winter?
What are the antifreeze measures for concrete?
Anti-freezing can be carried out using the greenhouse method or the thermal storage method. In fact, it is to add some materials to the surface of the pouring block for heat preservation. After the concrete is constructed, it must be covered with insulation materials to prevent it from being exposed to the cold winter.
Antifreeze needs to be operated from two aspects:
Use antifreeze: Antifreeze can greatly reduce the freezing point of mixing water and prevent the freezing and expansion of water inside the concrete in the plastic state and early stage. , frostbitten concrete.
How to prevent concrete from freezing?
Anti-freezing measures for concrete include:
1. Before concrete pouring, set up a wind-shielding wall and a greenhouse on the working surface to measure the temperature to ensure that the temperature inside the pouring room is above 5 degrees. If the temperature does not reach Fires and electric heaters can be used to raise the temperature to 5 degrees, and the temperature rise should be carried out before concrete pouring;
2. Measure the temperature of the incoming concrete. The temperature of the exiting tank is above 10 degrees, which does not meet the requirements. The concrete is withdrawn from the site and the pump pipe is insulated to ensure that the mold entry is greater than 5 degrees Celsius.
3. After the concrete pouring is completed, first cover it with a film and a quilt, and continue to raise the temperature indoors to maintain it above 5 degrees for 3 days until it reaches the critical strength of freezing.
What should be added to concrete to prevent freezing?
Concrete antifreeze measures in winter include adding antifreeze, preheating the material, etc. If the construction environment temperature is below zero, then an appropriate amount of antifreeze can be added to the concrete to lower the freezing point during mixing, thus ensuring that the concrete can be constructed normally. Material preheating means that the sand and mixing water are preheated before mixing the concrete.
What antifreeze measures are needed for concrete?
After concrete is frozen, it will crack and its strength will be greatly reduced, seriously affecting the safety of the structure. The main measures that should be taken during winter construction are: 1. Adjust the mix ratio and add qualified concrete antifreeze to the concrete; 2. Heating of concrete raw materials and insulation of transportation equipment to increase the penetration of concrete. Mold temperature;
3 After the concrete is poured, immediately cover it with plastic sheeting and insulation materials. The thickness of the insulation material should meet the thermal calculation requirements to ensure that the concrete reaches the critical strength before the temperature drops to zero.
For detailed requirements, please refer to the concrete chapter of the "Winter Construction Regulations for Construction Projects".
What measures should be taken to prevent freezing after concrete construction?
If you encounter a cold winter after concrete construction, proper maintenance methods should be adopted to prevent early freezing of concrete. Generally, the specific method should be selected based on the temperature conditions, structural characteristics and on-site energy conditions, as follows:
1. It is generally required that the concrete temperature when starting curing should not be lower than 5°C.
2. When the minimum temperature is not lower than -15°C and the surface coefficient of the structure (ratio of surface area and volume) is not greater than 5, the thermal storage method should be used for ground or underground projects. When preparing concrete at negative temperatures, water and sand can be heated appropriately, but the temperature of the water and sand mixture should not exceed 40°C, otherwise false setting will easily occur when cement is added.
3. In winter, concrete can also be mixed with early strength agent, antifreeze, etc. to lower its freezing point and harden the concrete at negative temperatures. When chloride salt is mixed into concrete (for unreinforced concrete), its dosage must be strictly controlled. Chloride salt cannot be added to prestressed concrete structures, or buildings that are frequently exposed to moisture or are close to high-voltage power sources.
4. Pay attention to the adaptability of the cement used, conduct thermal calculations, strengthen insulation and wind protection, and control the heating, constant temperature, and cooling speeds of artificial heating to prevent the concrete from freezing or drying out.
5. Air-entraining agents can be added when preparing concrete in winter. The purpose is to utilize the large number of evenly distributed micropores contained in the concrete to slow down the damage to the capillary structure of the concrete by the freezing pressure of free water. , thereby improving its frost resistance, but the increase in air content will affect the compactness and strength of concrete and should be controlled.
What are the requirements of concrete anti-freeze regulations?
① When ordinary concrete is prepared with Portland cement or ordinary Portland cement, it should be 30% of the designed concrete strength standard value;
It is prepared with slag Portland cement When the concrete strength grade is C10 and below, it should be 40% of the designed concrete strength standard value; however, when the concrete strength grade is C10 and below, it shall not be less than 5.0MPa.
② For concrete mixed with antifreeze, it shall not be less than 4.0MPa when the outdoor minimum temperature is not lower than -15℃; when the outdoor minimum temperature is not lower than -30℃, it shall not be less than 5.0MPa.
How to prevent freezing and heat preservation of concrete in winter?
Mainly start from three aspects: material ratio, raw material preheating, and thermal insulation maintenance.
Material ratio: Improving the strength level of concrete, reducing water consumption, and adding concrete antifreeze can all play an antifreeze role;
Preheating of raw materials: Stir with hot water, mix the stones Steam preheating, etc., can increase the mold entry temperature of concrete, allowing the concrete to reach critical freezing strength (about 4~5MPa) faster;
Insulation and maintenance: After the concrete is poured, insulation measures such as covering with plastic film, straw bags, and rock wool quilts should be taken to ensure that the temperature of the concrete surface is not lower than 5°C, so that the concrete can solidify normally and is protected from freezing. After reaching critical strength, it will not be frozen.
It should be noted that if the average temperature is lower than -5℃, the above three measures need to be carried out at the same time, or at least two of them are used. It cannot be understood that after adding antifreeze, insulation and maintenance are no longer needed. . Generally, winter projects use a combination of adding antifreeze and thermal insulation curing. Antifreeze can lower the freezing point and accelerate cement hydration, but it can only ensure that the concrete will not be frozen. Insulation and curing are also needed to ensure the normal development of the later strength of the concrete.
How to maintain concrete in winter?
The methods for concrete maintenance in winter are as follows:
1. If the temperature will not fall below zero, do a good job for more than one week after pouring. The concrete can be insulated;
2. If concrete is poured in negative temperatures, that is, the lowest temperature is below minus 5 degrees, the main thing to pay attention to is the early anti-freeze of the concrete.
Antifreeze needs to be operated from the following two aspects:
1. Use antifreeze: Antifreeze can greatly reduce the freezing point of mixing water and prevent moisture inside the concrete in the plastic state and early stage. Freezing expands and frostbites concrete. Antifreeze has no obvious harm to the strength performance of concrete. However, some antifreeze contains urea, and the concrete will release ammonia smell for a long time;
2. Insulation: Use plywood, wooden boards, etc. as much as possible. For formwork with a certain thermal insulation effect, insulation materials such as quilts, straw curtains or foam insulation boards are used to cover the exposed concrete surface and wrap the steel formwork to make the concrete strength develop faster. </p
微信扫一扫打赏
