Contents of this article
What is the applicable temperature of early strength antifreeze?
Instructions for use of early strength antifreeze?
At what temperature is antifreeze usually used on concrete?
Concrete initial setting time and anti-freezing measures?
What are the requirements for a thermometer chamber for winter use?
How much early-strength antifreeze should be added per m3 of concrete?
Can early-strength antifreeze be used as cement?
What is the applicable temperature of early strength antifreeze?
Hebei Zhusheng Building Materials Technology Development Co., Ltd. produces ZS-102 early-strength antifreeze, which has anti-freezing, lowering freezing point, and significant early-strength effects during use. It can shorten the natural curing time of concrete and improve Frost resistance and impermeability of concrete.
It is an antifreeze composed of components such as water reduction, early strength, freezing point reduction, and frost damage prevention. It has multiple functions such as early strength, antifreeze, appropriate air entrainment, and corrosion protection.
Significantly improves the early strength, and the strength continues to increase in the middle and late stages. It is an ideal admixture product for winter construction.
Early-strength antifreeze is suitable for mortar and concrete projects within the range of -15℃.
Early strength antifreeze instruction manual?
It has obvious early strength, air entrainment and anti-freeze effects. It can be used in concrete construction with the lowest daily temperature of 0℃~-20℃, and has no rust effect on steel bars.
Scope of application:
Poured-in-place or precast concrete for various industrial and civil buildings, various steel bars and prestressed reinforced concrete for highways, airports, tunnels, bridges, etc.
Technical indicators of early-strength antifreeze:
The project standard stipulates the technical indicators of first-class early-strength antifreeze
Water reduction rate (%) ≥ 810
p>Air content (%) ≥ 2.53.0
Bleeding rate ratio (%) ≤ 10035
Compressive strength ratio (%) specified temperature ℃-5 -10-15-5-10-15
R-7d201210251612
R28d959590110110110
R-7+28d95908510810095
R-7 +56d100115110105
Setting time difference (min) Initial setting-120~+120+30
Final setting-120~+120+45
Impermeability height ratio (%)≤10070
Alkali content (kg/m3)≤10.65
90d shrinkage ratio (%)≤120105
50 freeze-thaw strength loss Rate ratio (%) ≤ 10055
The corrosion effect on steel bars should indicate that there is no rust or corrosion on steel bars
Homogeneous performance:
Appearance: light gray powder; Moisture content: ≤3%; Fineness: 0.315 sieve all passed; cement slurry fluidity ≥150mm
At what temperature is antifreeze generally used for concrete?
When concrete antifreeze is constructed at 0~ -5℃, 4~6% can be added; when constructed at -5~ -10℃, 5~8% can be added; -10~ - For construction at 15℃, 8~10% can be added. The lower the service temperature of concrete, the better the antifreeze effect of the antifreeze. The concrete has more time (including negative temperature areas) to grow in strength, thereby greatly increasing the possibility of reaching critical anti-freeze strength. The usage standard is the dosage corresponding to the temperature. The temperature is above zero within 24 hours, and then below minus 2°. It has little effect on the concrete, but the concrete surface should be covered with insulation materials.
Concrete initial setting time and anti-freezing measures?
The initial setting time of concrete in winter is generally 8 to 12 hours, and the final setting time is 12 to 16 hours. If the temperature is below zero in winter (more than a week after pouring), just do a good job of concrete insulation. If concrete is poured in a negative temperature environment (temperature below minus 5°C), the main thing to pay attention to is early concrete anti-freeze. Antifreeze needs to be operated from two aspects:
1) Use antifreeze: Antifreeze can greatly reduce the freezing point of the mixing water, preventing the moisture inside the concrete from freezing and expanding in the plastic state and early stage, and causing frost damage to the concrete. Antifreeze has no obvious harm to the strength performance of concrete, but some antifreeze contains urea, and the concrete will release ammonia smell for a long time, so special attention is required.
2) Insulation: Use plywood, wooden boards and other formwork with a certain insulation effect as much as possible. Use insulation materials such as quilts, straw curtains or foam insulation boards to cover the exposed concrete surface and wrap the steel formwork to make the concrete Strength develops quickly. For winter construction, use early-strength silicate or ordinary Portland cement because the strength develops quickly and the heat of hydration is relatively high. However, as long as the insulation is good, any cement can be used. The strength develops more slowly, which is better for preventing thermal stress cracks. In an environment with a temperature of 2°C, antifreeze may not be used when pouring concrete, but insulation must be done and the temperature change trend must be paid close attention to. If the temperature continues to drop, it is necessary to strengthen the concrete insulation and pay close attention to the temperature change trend. If the temperature continues to drop, concrete insulation needs to be strengthened.
What are the requirements for winter temperature measurement chambers?
Answer: 1. Requirements for concrete mixing temperature measurement
During concrete construction in winter, mixing temperature measurement (including on-site mixing and commercial concrete) should be carried out and recorded. The temperature measurement records of concrete mixing during winter installation include atmospheric temperature, raw material temperature, tank exit temperature, mold entry temperature, etc. The specific requirements for temperature measurement should be explained in writing, and the executor must operate in accordance with the regulations. Generally: For mixed concrete, the temperature of the concrete coming out of the tank and entering the mold should be checked frequently (not less than 4 times per shift). The temperature of the concrete or mortar coming out of the tank is required to be not less than 10°C, and the temperature of the concrete entering the mold is not lower than 5°C. .
After the original record is signed, it should be submitted to the document clerk for filing. Fill in the "Remarks" column with the words "On-site mixing or commercial concrete". Each temperature value in the table must be marked with a plus or minus sign.
2. Concrete curing temperature measurement records
(1) The winter construction of concrete should comply with national standards.The current national standard "Construction Regulations for the Winter Period of Construction Projects" (JGJl04) and the provisions of the construction technical plan.
(2) The concrete mixed with antifreeze is measured every 2 hours before it reaches the critical anti-freeze strength (4MPa). When it reaches the critical anti-freeze strength (4MPa) and the temperature changes normally, the temperature measurement interval can be calculated by 2h is adjusted to 6h.
Control the number of temperature measurements: measure the temperature immediately after the concrete is poured as the first temperature measurement, and then measure it every 2 hours for three consecutive days. After three days, measure it every 4 hours (morning) 8:00, 8:00 pm, 2:00 pm) until the concrete temperature is 0℃.
(3) Temperature measurement for concrete winter maintenance should first draw a layout diagram of temperature measurement points (indicate the names of specific parts), including the location and depth of the temperature measurement points. The temperature measurement record should include the atmospheric temperature, the actual measured temperature of each temperature measuring hole, the average temperature and interval time of each temperature measuring hole measured at the same time, etc. In addition, maturity calculations (this time, cumulative) should also be carried out. Each temperature value in the table must be marked with a plus or minus sign.
(4) Regarding temperature measurement items, temperature measurement times and temperature measurement hole settings, the current relevant standards shall be implemented as required.
① When selecting the location of the temperature measuring hole, choose the location where the temperature changes greatly, where it is easy to lose heat, or where it is prone to freezing. More locations should be located in the northwest or in the front shade. The mouth of the temperature measuring hole should not be Set into the wind and temporarily closed.
Pre-embedded temperature measuring pipes: After the concrete is poured and before covering, the temperature measuring pipes must be pre-buried. The specific embedded positions and quantities must be drawn in advance. Please do the numbering.
②Setting of structural measuring holes
A. Beams (including simple supports and connecting beams): The temperature measuring holes on the beam should be perpendicular to the axis of the beam, and the hole depth is the height of the beam. 1/3 to 1/2.
B. Cast-in-situ reinforced concrete structural columns: A temperature measuring hole is provided at the lower end of each structural column.
C. Base plate: The temperature measuring holes on the base plate are arranged at a distance of no more than 5m in the vertical and horizontal directions. Each room has an area of no more than 20m2. One temperature measuring hole can be set up. The temperature measuring hole is perpendicular to the board surface and the hole depth is It is 1/3 to 1/2 of the plate thickness.
D. Cast-in-situ concrete wall panels: When the wall thickness is 20cm or less, a temperature measurement hole is provided on one side, and the hole depth is 1/2 of the wall thickness; when the wall thickness is greater than 20cm, a temperature measurement hole is provided on both sides. Set up a temperature measuring hole with a depth of 1/3 of the wall thickness and not less than 10cm. The temperature measuring hole is at an inclination angle of 30 degrees with the board surface. Temperature measuring holes on large-area walls are arranged at intervals of no more than 5m in both vertical and horizontal directions; when the area of each wall is less than 20m2, one temperature measuring hole can be set on each side.
3. Temperature measurement records for mass concrete curing
During mass concrete construction, the atmospheric temperature, temperature of each temperature measuring hole, internal and external temperature differences and cracks should be inspected and recorded. Temperature measurement for mass concrete curing should be accompanied by a temperature measurement point layout diagram, including the layout location and depth of the temperature measurement points, etc. Each temperature value in the table must be marked with a plus or minus sign.
4. Temperature measurement requirements
⑴ When measuring, proceed in the order of measuring hole numbers. After inserting the thermometer into the temperature measuring hole, block the orifice and leave it in the hole for 3-5 Take readings after 10 minutes;
⑵ The temperature of concrete coming out of the tank, pouring and entering the mold should not be less than 4 times per working shift;
⑶ When the heat storage method is used for curing, during Measure once every 6 hours;
⑷ For concrete mixed with antifreeze, measure once every 2 hours before the strength reaches 4.0Mpa, and then measure once every 6 hours;
⑸ There is an outdoor atmospheric measurement record sheet for winter construction;
⑹ Use the maturity method to estimate the strength of concrete.
How much early-strength antifreeze should be added per m3 of concrete?
3-6% early strength antifreeze of cement should be added to every m3 of concrete. Introduction: Concrete antifreeze early strength admixture refers to an admixture that can improve the early strength of concrete and has no significant impact on the later strength. The main function of early strength agent is to accelerate the hydration rate of cement and promote the development of early strength of concrete; it has both early strength function and certain water reduction and enhancement function. Concrete early strength agent is one of the earliest types of admixtures used in the history of admixture development. So far, people have developed a variety of early-strength additives other than chloride and sulfate, such as nitrite, chromate, etc., as well as organic early-strength additives, such as triethanolamine, calcium formate, urea, etc. On the basis of early-strength additives, a variety of composite admixtures are produced and applied, such as early-strength water-reducing admixtures, early-strength antifreeze and early-strength pumping agents. These types of early-strength admixtures have been used in actual projects and have played an important role in improving concrete properties, increasing construction efficiency and saving investment costs.
Can early-strength antifreeze be used as cement?
Cement antifreeze is harmless when the dosage is less than 5% of the cement dosage. When the dosage is large, it will cause false setting of cement and reduce the strength of cement mortar or concrete. Therefore, it must be used in strict accordance with the laboratory mix ratio. Ingredients.
Ordinary Portland cement has no effect. The traditional method is to add brine during the stirring process. Special cement has strict requirements, and ordinary antifreeze cannot meet the requirements.
The addition of antifreeze must be carried out in accordance with the data given by the laboratory. If too much is added, false setting, reduced strength, and reduced slump of the concrete will occur. </p
微信扫一扫打赏
