With the development of the concrete industry, the use of various raw materials , cement and other mixed products have increasingly higher requirements for different parts, structural components and construction methods during construction. The results show that the setting time will prolong with the increase in the amount of retarder. At the same time, different types of additions have great differences in the impact on the setting time. As the temperature increases, the setting time will shorten significantly. The setting time of the admixture can be directly controlled. What are the functions of retarders that affect the progress of construction and other issues? As an industry professional, you must understand clearly. Ultra-early strength and ultra-retarded setting are both important research topics in concrete. Rapid determination of whether admixtures exceed the standard can better serve the industry and provide reference for industrial production.
Early water of Portland cement The hydration process is divided into four stages, namely: initial reaction period, hydration reaction occurs immediately after cement and water are mixed, C3S generates hydrated calcium silicate and releases Ca(OH)2; C3A mineral dissolves in water and quickly reacts with The dissolved gypsum reacts to precipitate ettringite, which adheres to the surface of the cement particles to form a thin film coating. During the rest period, the plasticity of the cement slurry remains basically unchanged because the thin film coating formed during the initial reaction period hinders further hydration of cement and water. Change; setting period, about 6 to 8 hours after the cement is mixed with water, the cement will set.
When the film on the surface of the cement particles is wrapped When the cement layer ruptures, it continues to hydrate, resulting in the setting period; the hardening period, after the setting period, enters the hardening period. At this time, the hydration rate of the cement is slow, but it continues, hydrates continue to fill the capillary pores, and the strength continues to increase. .
What are the functions of coagulant? A small admixture that prolongs the setting time of concrete. In order to prevent the cement product from prematurely solidifying and losing its plasticity when the temperature is high or the transportation distance is long, which will affect the pouring quality, and to prevent quality accidents such as cold joints, it is often added. Commonly used organic retarder: wood sulfonates and their derivatives, hydroxycarboxylic acids and their salts, sugars and their derivatives, organic phosphoric acid and its salts, acrylic copolymers, etc.; inorganic include: phosphates , borax, zinc salt, etc.
When producing building gypsum products, according to Depending on the needs of the production process, chemicals such as citric acid, trisodium citrate, tartaric acid, boric acid, and phosphates can be directly used as retarder. This kind of main function is better in retarding effect. When used, it can generally be pre-dissolved in water according to a certain proportion, and then the gypsum powder can be mixed with an aqueous solution containing a retarder. However, these will affect the strength of gypsum, and the amount should be reduced as much as possible when using it.
Can be introduced during the mixing process of concrete An admixture with a large number of uniformly distributed, stable and closed tiny bubbles is called an air-entraining agent. Air-entraining agents are more suitable for applications where the strength requirements are not too high and the water-cement ratio is large, such as hydraulic large-volume concrete; concrete which requires high durability such as frost resistance also needs to be mixed with air-entraining agents
In summary: the role of the retarder is to improve and retard the solidification of the cement product At that time, Qingdao Dingchang New Materials Co., Ltd. developed a new type of retarder that can replace sodium gluconate in equal or excessive amounts. The price is favorable and it is much easier to adjust the setting time of concrete than sodium gluconate. It can be adjusted according to the floor materials and conditions of each region. temperature and adjust the dosage appropriately. It can reduce the slump loss over time and adjust the workability. At the same time, it has a certain auxiliary water-reducing effect and is suitable for various types of water-reducing mother liquors. </p
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