Brief Introduction of Cement Viscosity Modifying Agents
Keywords
Viscosity Modifying Agents, VMA, Viscosity modifier, cement, self-compacting concrete, polycarboxylate superplasticizer
Viscosity Modifying Agents (VMA) is a macromolecular material used to improve the cohesion and stability of cement-based cementitious material systems.
K.H.Khayat divides viscosity modifiers into the following types:
I. Water-soluble synthetic and natural organic polymers.
This viscosity modifiers mainly include xanthan gum, wenlun gum, fiber
Vitamin ether, polyoxyethylene, polyacrylamide, polyvinyl alcohol, etc., they can increase the viscosity of mixing water.
II. Water-soluble organic flocculant.
This type of viscosity modifier mainly includes styrene copolymers containing carboxyl groups, polymer electrolytes, natural gums, etc., which are adsorbed on the surface of cement particles and increase the viscosity of the slurry by enhancing the interaction force between cement particles. increase.
III. Organic latex material.
This viscosity modifiers mainly include acrylic emulsions and aqueous clay dispersions. They can enhance the interaction between cement particles and provide additional ultra-fine latex particles to the cement paste system.
IV. Water-swellable inorganic materials.
This viscosity modifiers mainly include bentonite, silica fume, and ground asbestos. This type of viscosity modifier has a super large specific surface area, which greatly enhances the water retention capacity of the slurry.
V. Non-water-swellable inorganic materials.
This viscosity modifiers mainly include fly ash, lime powder, metakaolin, limestone powder and diatomaceous earth. This type of viscosity modifier also has a high specific surface area and can increase the content of fine particles in the slurry.
Application background
High-strength and ultra-high-strength concrete use high-strength grade cement, increase cementitious materials, and reduce water-cement ratio to increase concrete strength, but the above measures will lead to increased concrete viscosity and decreased fluidity.
The combination of viscosity modifier and polycarboxylate high-efficiency superplasticizer is applied to self-compacting concrete, which can not only realize high-strength concrete, but also improve the pumpability of concrete.
