What is the function of retarder in gypsum?
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In recent years gypsum has been used more and more widely in the construction engineering, and the use of gypsum based dry mortar has become the main product of dry mortar. For example, as the interior wall plastering material, plastering gypsum has the functions of light weight, anti-inflammatory, sound insulation, heat preservation, sound absorption, etc. It is the preferred material to replace the traditional mortar plastering. Gypsum building materials such as gypsum board, gypsum block, gypsum joint filler agent, gypsum strip board, self leveling gypsum and gypsum board adhesive have been widely used in the construction industry at home and abroad, as shown in picture 4.5-1.
The raw material of gypsum in China is mainly hemi-hydrate gypsum, containing a small amount of over-burned gypsum, which is a kind of pneumatic cementitious material. The setting time of hemi-hydrate gypsum is usually 3~10 min after encountering water, which brings a lot of inconvenience to the construction. At the same time, due to the fast setting, it has a negative impact on the bond strength and the final product quality. Therefore, it is very important to effectively control and extend the setting time of gypsum products. For the construction requirements of gypsum based products, the opening time shall be at least 2-3h to ensure the normal construction. In the field construction, the gypsum products close to the solidification can not be reused with water. Gypsum retarder has become one of the indispensable additives in all gypsum based products.
Picture 4.5-1 Initial setting time (min) and dosage (%)
The commonly used gypsum retarders are mainly modified protein, citrate, tartrate and potassium hydrogen phosphate. Although these retarders can effectively extend the opening time of gypsum products, they also affect the later strength of gypsum products.
At present, the domestic gypsum retarder can effectively solve the problem of gypsum setting too fast. The imported products are mainly gypsum retarder series produced by TRICOSAL company of Germany. The main component is calcium salt of polymethyleneaminic acid, pH value 12, chlorine content <0.1%, good solubility in water. The operation time of gypsum products can be adjusted according to the amount of addition, without negative impact on the strength and cohesiveness of the final products. With the addition of gypsum commercial retarder, the hydration heat of gypsum in the hydration reaction can be greatly reduced, so as to avoid cracking and bond strength reduction caused by rapid hydration reaction.
What is gypsum retarder?
What is gypsum retarder?
gypsum retarder is a chemical additive used in the production of gypsum-based materials, such as plaster, wallboard (drywall), and gypsum-based mortars. Its primary function is to slow down the setting time of gypsum, allowing for extended workability and a more controlled setting process. Heres an overview of gypsum retarders:
Function:
Delaying Setting Time: The main function of a gypsum retarder is to delay the setting time of gypsum-based materials. This prolongs the workability of the material, allowing for easier handling, application, and finishing.
Composition:
Chemical Agents: Gypsum retarders typically contain chemical compounds that interfere with the hydration process of gypsum. Common retarder agents include organic acids, phosphates, lignosulfonates, gluconates, and other proprietary formulations.
Admixtures: Gypsum retarders may be supplied as liquid or powder admixtures that are added to the gypsum-based material during mixing or manufacturing.
Properties and Characteristics:
Extended Workability: Gypsum retarders allow for extended workability of gypsum-based materials, giving users more time to apply and manipulate the material before it sets.
Improved Finish: By slowing down the setting time, gypsum retarders can help achieve a smoother and more uniform surface finish, reducing the risk of surface defects such as cracking or unevenness.
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Controlled Setting: Retarders provide better control over the setting process, allowing for adjustments to be made to the materials consistency and application technique as needed.
Applications:
Construction: Gypsum retarders are commonly used in the construction industry for the production of gypsum-based products such as plaster, wallboard, joint compound, and gypsum-based mortars.
Art and Sculpture: In art and sculpture, gypsum retarders may be used to extend the working time of gypsum plaster or casting materials, allowing artists to create intricate designs and details.
Safety and Handling:
Gypsum retarders should be handled and used in accordance with manufacturer instructions and safety guidelines.
Protective equipment such as gloves, goggles, and masks should be worn when handling gypsum retarders to avoid skin contact, inhalation, or ingestion.
Proper storage conditions should be maintained to prevent contamination or degradation of the retarder product.
Compatibility:
Its important to ensure that the gypsum retarder selected is compatible with the specific gypsum-based material being used. Compatibility testing may be necessary when using retarders with different gypsum formulations or additives.
Gypsum retarders play a crucial role in controlling the setting time and workability of gypsum-based materials, offering benefits such as extended working time, improved finish, and better process control. By selecting the appropriate retarder and using it correctly, manufacturers and users of gypsum-based products can achieve optimal performance and quality in their applications.
Post time: Feb-10-For more information, please visit Gypsum Retarder Suppliers.
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