What are the common reasons for using retarder?

High-efficiency retarder is mainly a concrete admixture composed of retarder, air-entraining and other components, and has the properties of super plasticization, high water reduction, and good water retention. This product implements the standards GB8076-1997 "Concrete Admixtures", GB/T8077-2000 "Test Methods for Homogeneity of Concrete Admixtures", GB18588-2001 "Limits of Nitrogen Released by Concrete Admixtures"

II. Product Features

1. Excellent retarding and water-reducing enhancement effect.

2. Improve the workability of concrete.

3. Significantly reduce the early hydration heat of cement and delay the appearance of the hydration heat peak.

4. It can accelerate the hardening of concrete after final setting.

5. No corrosion effect on steel bars.

3. Product use

1. Various industrial and civil construction, water conservancy, transportation, ports, municipal and other projects.

2. Precast and cast-in-situ concrete, reinforced concrete and prestressed concrete.

3. Retarded or ultra-retarded concrete, concrete that needs to be parked for a long time or transported over long distances, and self-leveling and vibration-free concrete.

4. Large-volume concrete, roller compacted concrete, concrete constructed in hot climate conditions, concrete poured in large areas, and concrete that avoids cold joints.

5. Prepare high-strength and high-performance concrete.

6. Special cement can be prepared according to user needs, and stick concrete admixtures with different performance requirements can be mixed with various mixed materials.

IV. Recommended dosage

The dosage should be determined according to different engineering technical requirements and through trial mixing. Generally speaking, the dosage of powder can be within the total amount of cementitious materials. Adjust within the range of 0.5-1.5%, the recommended dosage is 1.0%, and the liquid dosage is converted according to the solid content. In case of special circumstances, you can consult our company.

5. Instructions for use

1. Add this agent and mixing water into a mixer and mix. The mixing time should refer to national standards. Forced mixers should be used to produce high-strength concrete.

2. The secondary mixing method can also be used as needed.

3. The specific usage method should follow GB50119-2003 "Technical Specifications for the Application of Added Jingxin to Concrete"

6. Precautions

1. After this product is over-admixed , the setting time will be extended.

2. When this product is over-doped and under-doped, the working performance will be reduced and the slump loss will be accelerated. Not affected.

3. This product is suitable for concrete construction where the daily minimum temperature is above 5℃.

4. When this product is used in combination with other types of admixtures, attention should be paid to its compatibility, and tests should be conducted before use.

5. When the cement variety is changed or new cement is imported, the adaptability of the admixture and cement should be tested and used only if it meets the requirements.

Admixtures that delay the setting time of concrete without significant impact on later strength. The main ingredients are polyhydroxy compounds, hydroxycarboxylates and their derivatives, and high-sugar lignosulfonates. Because they also have water-reducing properties, they are also called retarding water-reducing agents. In addition, some inorganic salts such as zinc chloride, borate, and various phosphates also have a retarding effect. ⑤ Admixtures to improve durability: air-entraining agents, waterproofing agents, anti-rust agents, etc. The dosage is 0.1~0.6% of the cement dosage. Retarder is suitable for continuous pouring of concrete, large volume concrete, ready-mixed concrete and pumped concrete under high temperature conditions.

Magnesite cementitious materials will release a lot of heat when they are hydrated. When the temperature is high in summer, the temperature of some products reaches 80 degrees. When the temperature of the products is too high, the products produced will no longer be 5.1 .8 phase, but the very unstable 9.1.5 phase, and its strength is not high. When the temperature is too high, magnesite products produced will have problems such as halogenation, deformation, and low strength. The current solution is to add a retarder to disperse the heat of hydration and control the setting time.

In 2005, the material industry standard WB/T 1023-2005 of the People's Republic of China was promulgated, and the definition of retarder is: an admixture that can delay the setting time of magnesite gelled products.

Testing index:

Flow rate increase: 8

Initial setting time difference: +60~+120

Compressive strength ratio 7 Days: 120

Compressive strength ratio 28 days: 120

Softening coefficient: 0.55

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