What are the common types of water reducing agents?

   What kinds of water reducing agents are commonly used in engineering and what are their characteristics?

   At present, water reducing agents are mainly lignin-based, naphthalene-based, resin-based, molasses-based, and polycarboxylic acids. There are also air-entraining agents and non-air-entraining agents. According to its influence on concrete setting and hardening speed, it can be divided into three types: ordinary type, early strength type and slow setting type.

(1) lignosulphonate water reducer
The main variety is calcium lignin sulfonate, a brownish-yellow powder obtained from the extraction of alcohol, wood pulp waste liquid, evaporation, sulfonation, and spray drying. Water agent. Its suitable dosage is 0.2% to 0.3%, and the water reduction rate is about 10%. If the water is not reduced, the slump can be increased by about 10cm, and the 28d strength of the concrete can be increased by 10% to 20%. Cement 10%; However, wood calcium has retarding effect on concrete, generally retarding for 1 to 3 hours. It has stronger retarding property at low temperature, too much content and serious retarding. In addition, wood calcium is an air-entraining and water-reducing agent, which increases the air content of concrete from 2% when it is not mixed to 3.6%. This has an impact on the strength of concrete, but is beneficial to the frost resistance of concrete.

(2) naphthalene formaldehyde water reducer
The naphthalene-based water reducing agent is naphthalene and homologues of naphthalene fractionated from coal tar. After sulfonation and condensation. It has a strong dispersing effect on cement, so its effects of reducing water, enhancing, and improving durability are better than lignin, which is a highly effective water reducing agent. Generally, the water reduction rate is above 15%, the early strength is significant, and the concrete is reinforced by more than 20% at 28 days. The suitable dosage is about 0.5% to 1.5%, and the PH value is 7-9. It is suitable for all concrete projects, and more suitable for the preparation of high-strength concrete and fluidized concrete.

(3) Molasses water reducing agent
Molasses-based water reducer is a waste brown liquid extracted from sugar during the production process of a sugar factory as a raw material, and neutralized with salt to form a tan powdery solid or paste liquid. In addition to its functions, it also has a significant retarding effect, so it is a retarding type water reducing agent, which generally extends the initial setting and final setting time by more than 3h. Its suitable dosage is 0.2% to 0.3%, water reduction rate is 6% to 10%, and the strength of concrete at 28d is increased by 15% to 20%. If the original strength is maintained, the cement can be saved by about 10%.

(4) Polycarboxylic acid water reducing agent (master batch is macromonomer HPEG-2400)
Polycarboxylic acid superplasticizer has a special comb-like structure, which promotes the dispersion of cement particles through electrostatic effects and steric hindrance effects, improves the workability of concrete mixtures, can effectively reduce water consumption, and improve physical properties of concrete. Including concrete compressive, tensile, flexural strength and elastic modulus, improving concrete frost resistance and impermeability; adjusting the setting time of concrete, improving the construction performance of concrete; at the same time, it can reduce water bleeding and improve concrete compactness And other effects to improve the durability of concrete. Its effective dosage is 0.1% ～ 0.2%. It has strong dispersibility, low dosage, low slump loss of concrete, good compatibility with different cements, and does not cause obvious retardation. gas.