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.
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At present, the domestic gypsum retarder can effectively solve the problem of gypsum setting too fast.
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.
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.
Gypsum retarder plays an important role in building materials and has significant advantages.
The Function Of Gypsum Retarder:
1.Extend the setting time of gypsum:
Gypsum retarder can significantly prolong the hydration time of gypsum from hemi-hydrate gypsum to dihydrate gypsum, thereby delaying the setting rate of gypsum. This is particularly important for construction operations as it provides more time for workers to smooth and finish, ensuring a smooth and aesthetically pleasing final surface.
2.Improve the fluidity of gypsum:
The use of gypsum retarder can also increase the fluidity of gypsum, making the filling of gypsum slurry in complex molds more uniform and improving the overall quality of the finished product
3.Enhance the strength of gypsum:
Modern gypsum retarders not only improve the efficiency of gypsum construction, but also focus on enhancing its strength to ensure the stability and durability of gypsum building materials during use.
4.Control the crystal structure of gypsum:
Some gypsum retarders can alter the crystalline structure of gypsum, thereby further optimizing its physical properties such as water resistance and adhesive strength.
Advantages Of Gypsum Retarder&#;
1.Improve construction efficiency:
By extending the setting time of gypsum, gypsum retarders provide construction personnel with more ample operating time, avoiding rework and waste caused by rapid gypsum setting, thereby improving construction efficiency.
2.Improve construction performance:
The use of gypsum retarder makes gypsum slurry more fluid, facilitating filling and shaping in complex molds, and reducing construction difficulty.
3.Improve the quality of finished products:
Longer setting time and better flowability result in improved surface smoothness, uniformity, and overall quality of gypsum products.
4.Expand the scope of application:
Due to the ability of gypsum retarders to enhance the water resistance and adhesive strength of gypsum, the application range of gypsum building materials in humid environments and exterior wall decoration has been expanded.
5.Environmental protection and energy conservation:
By extending the curing time of gypsum and improving its physical properties, gypsum retarders help reduce reliance on high-temperature curing, lower energy consumption, and align with the development trend of modern building energy conservation and environmental protection.
In summary, gypsum retarders play a crucial role in gypsum building materials and have significant advantages. In practical applications, the appropriate type of retarder should be selected based on specific construction conditions and gypsum types, and the amount added should be accurately calculated to ensure construction quality and efficiency.
With over 20 years of industry experience, Celotech can continuously accumulate professional knowledge and innovate and improve in technology, products, or services.
In the field of Gypsum Retarder&#;our brand Gypstar®Gypsum Retarder can significantly improve the efficiency while at the same time save cost and give flexibility to gypsum bonding agent or gypsum plaster by prolong the open time.
Want more information on retarder gypsum? Feel free to contact us.
Besides, we will actively participate in exhibitions related to the construction (wall putty, dry-mixed mortar, tile adhesives, etc.) and coatings (paint and coating additives, etc.) industries, and integrate the exports of Celopro® HPMC/MHEC/HEC/CMC produced and operated by our company, together with products including RDP, starch ether, etc.; relying on Celotech&#;s 20 years of professional cellulose ether research and development and sales background, our company will go all out to strive to expand the market sales share of Celopro® products in Central Asia, South America and other countries.
ABOUT CELOTECH
&#;Celotech Chemical is a high-tech enterprise specializing in construction additives.
&#; Founded in , then gradually established branch company and R&D centers, etc. Celotech set up the production site in Shandong, China and is headquartered in Suzhou of Jiangsu province, a city very near Shanghai.
Concrete admixtures and retarders are popular materials used to enhance the mechanical properties of concrete and mortar. Nowadays, concrete retarders are highly preferred in hot weather to allow time to properly mix, transport, and place concrete wherever necessary.
Many construction chemical manufacturers provide concrete retarders but to get the best results it is always recommended by the experts to choose the best ones. Nevertheless, in this blog, we will explore all about concrete retarders including their mechanisms, types, benefits, and more.
To give idea about the concrete retarders, it is additives that are added to cement-based mixtures like mortar or concrete to delay the setting time of the cement paste. These are commonly known as concrete retarders, which are water-soluble additives that get easily dissolved in water.
When you add the concrete retarder in the concrete mix can result in extending the setting time of the concrete by approximately up to one hour. It basically slows down the hardening in warm or hot weather to allow construction workers more time to mix, deliver and pour the concrete. In fact, concrete retarders reduce the pace of the process while conserving water.
A concrete retarder is a type of admixture that temporarily stops the hydration process upon addition to the mixing water or on application to the surface of fresh concrete, thereby allowing additional time for the concrete to rest before it begins to harden.
The mechanism involved in such retarders depends on both the type of retarder and cement involved. It is worth noting that the retarder effects are temporary or for a short period of time, and after a certain period, its mechanism fades, and the watering goes back to normal.
Below are the four key ways retarders slow down the setting process:
A retarding additive forms a protective coating on the surfaces of the cement particles. The barrier reduces access by water molecules to the unhydrated cement, hence it retards the hydration reactions. As a result, the cement paste thus remains workable for a longer time due to the insufficient hydration produced to initiate hardening. The retarder complex with the C3A of cement and comes out of solution, incorporating into the hydrating material.
When water is added to it, the surfaces of cement particles release calcium and hydroxyl ions into the mix. When their concentration increases up to a certain critical amount, C2S and CS start crystallizing. In this process, the crystal nuclei of calcium hydroxide absorb the retarding admixture that delays further crystal growth until the point where the cement becomes supersaturated.
At the start of the process, calcium ions given out by the cement grains make some complex with other ions. It is easier to dissolve cement when these complex forms. In the liquid phase of the cement paste, during hydration with a retarding admixture, the concentrations of Ca²&#;, OH&#;, Si, Al, and Fe are increased. This buildup of calcium and hydroxyl ions interferes with the association between these ions and thus slows down the hydration process.
During precipitation, the retarder interacts with the highly alkaline solution to form insoluble derivatives. The phenomenon resembles with adsorption. In a few minutes of mixing water with cement, the pH of the solution goes beyond 12. These insoluble compounds create protective coatings around the cement particles, which slows down the hydration process. The coating forms a diffusion barrier that restricts the ability of water to reach the cement particles effectively.
This is all about the mechanism of concrete retarders and now let&#;s check out the types of concrete retarders.
There are broadly two categories of concrete retarders which are as follows:
Now, let&#;s understand how retarding additives acts on the concrete&#;s properties.
The above-mentioned effects can be observed when the concrete retarders are added to the concrete mixture. However, the best concrete retarder doesn&#;t affect the concrete properties after the setting time effect. Keep reading to know the various uses of concrete retarders.
There are various applications of concrete retarders to get the desired outcome in particular situations. The following are the uses of concrete retarder:
Now that you are aware of retarder additive uses, let&#;s have insights into the advantages of concrete retarders.
There are several advantages of concrete retarder which are as follows:
Each material has its own set of advantages and disadvantages when applied. Let&#;s explore some of the limitations of using concrete retarders.
The best concrete retards are always used in many great construction projects, however, you should also choose a branded one to get the best results in the construction process. Let&#;s have a look at one of the top-quality dry mix raw materials that can be used with the concrete admixtures.
Sodium Gluconate which is also known as Sodium Salt of Gluconic Acid which is a dry mix raw material, can be used as a setting time retarder. Our Sodium Gluconate is formulated under strictly controlled conditions through the fermentation of glucose. To give an idea about it, it is a white crystalline powder and easily soluble in water.
Our Sodium Gluconate is non-toxic, non-flammable, and non-corrosive. In short, Sodium Gluconate is an environment-friendly and biodegradable construction chemical. When it is added to cement, it inhibits hydration and slows down the setting time of the concrete mix.
To wrap up, a concrete retarder&#;s role is impressive in the construction industry as it delays the hydration process. It keeps the concrete workable and easier to handle for an extended period. Concrete retarders are specifically useful in hot and warm temperatures to allow time for workers to deliver, transport, and pour the concrete. However, it is very essential to buy this construction chemical from authorized and genuine manufacturers like Sakshi Chem Sciences Pvt Ltd.
We are one of the leading construction chemical manufacturers in India offering 200+ construction chemicals to construction companies, developers, builders, and various clients. Our trained team offers the best consultation, customized quotations, and assistance on quality products. So, if you are also searching for the best quality construction chemicals then get in touch with us.
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