Development History
The first generation of superplasticizers—naphthalene-based superplasticizers and melamine resin-based superplasticizers were developed in the early 1960s. Because of their performance compared to ordinary water-reducing agents, they were developed in the late 1930s. Lignosulfonate is a representative-it has a significant improvement, so it is also called a superplasticizer. The second-generation superplasticizer is sulfamate, although it is after the third-generation superplasticizer—polycarboxylic acid in chronological order. The graft copolymer with both sulfonic acid group and carboxylic acid group is the most important of the third-generation superplasticizers, and the performance is also the most excellent high-performance superplasticizer.
Main species
The water reduction rate of the superplasticizer can reach more than 20%. Mainly naphthalene series, melamine series and water reducers made from them, of which naphthalene series are the main ones, accounting for 67%. Especially in my country, most of the superplasticizers are naphthalene series superplasticizers with naphthalene as the main raw material. Naphthalene-based superplasticizers can be divided into high-concentration products (Na2SO4 content <3%), medium-concentration products (Na2SO4 content 3%-10%) and low-concentration products (Na2SO4) according to the level of Na2SO4 content in their products. Content>10%). Most naphthalene-based superplasticizer synthesis plants have the ability to control the content of Na2SO4 below 3%, and some advanced companies can even control it below 0.4%.
Naphthalene-based water-reducing agent is the largest and most widely used high-efficiency water-reducing agent in my country (accounting for more than 70% of the amount of water-reducing agent). It is characterized by a high water-reducing rate (15%-25%) and no air-entrainment. , Has little effect on setting time, has relatively good adaptability to cement, can be used in combination with various other additives, and the price is relatively cheap. Naphthalene-based water-reducing agents are often used to formulate high-fluidity, high-strength, and high-performance concrete. The slump loss of concrete mixed with naphthalene-based water-reducing agent is faster. In addition, the adaptability of naphthalene-based water-reducing agents to certain cements needs to be improved.
characteristic
The superplasticizer has a strong dispersing effect on the cement, which can greatly improve the fluidity of the cement mixture and the slump of the concrete, and at the same time greatly reduce the water consumption and significantly improve the workability of the concrete. However, some superplasticizers will accelerate the loss of concrete slump, and excessive mixing will cause bleeding. The superplasticizer basically does not change the setting time of concrete. When the amount is large (overdose incorporation), it has a slight retardation effect, but it does not delay the growth of the early strength of hardened concrete.
It can greatly reduce the water consumption and significantly increase the strength of concrete at various ages. When keeping the strength constant, 10% or more of cement can be saved.
The chloride ion content is very small, and it does not corrode the steel bars. It can enhance the impermeability, freeze-thaw resistance and corrosion resistance of concrete, and improve the durability of concrete.
Scope of application
It is suitable for precast and cast-in-situ reinforced concrete in various industrial and civil construction, water conservancy, transportation, port, municipal and other projects.
It is suitable for high-strength, super-high-strength and medium-strength concrete, as well as concrete that requires early strength, moderate frost resistance, and high fluidity.
Precast concrete components suitable for steam curing process.
It is suitable to be used as the water reducing enhancement component (ie master batch) of various composite admixtures.
skills requirement
The technical requirements for superplasticizers and slow-setting superplasticizers are defined by “Concrete Admixtures”