The rational use of bentonite can not only improve the performance of building materials, but also reduce the cost of materials and effectively save resources.
1. Overview of properties of bentonite
Bentonite is a silicate with a lamellar structure, and its main component is montmorillonite. Montmorillonite has a monoclinic crystal structure, consisting of two layers of silicon-oxygen tetrahedral wafers sandwiching a layer of aluminum-oxygen octahedral wafers. It is a 2:1 type layered silicate mineral.
The bonding force between the oxygen layers in the montmorillonite molecular structure is very small. Water and other polar molecules can easily enter between the crystal layers. At the same time, the cations in the structure can easily be replaced with other ions.
Application of Bentonite in Building Materials
2. Bentonite is widely used in building materials because of its good expansion and water absorption.
1. Material characteristics
(1) The crystal structure of bentonite allows water molecules to enter between its lattice layers. At the same time, because the molecular structure is negatively charged, the particles repel each other, and external pressure will not easily squeeze out the adsorbed water molecules.
(2) Bentonite has a small volume and a large specific surface area. In theory, it can absorb water equivalent to 8 to 20 times its own volume. After washing with water, it will be in a gelled state, which can effectively prevent the passage of water molecules and form a good waterproof layer.
3. Wall materials
Adding the characteristics of bentonite itself to wall materials can better realize the properties of the material, improve the functions of the wall materials, and tap better performance.
3. Cementitious materials
①White cement
Bentonite and other materials can be processed to produce white cement. Compared with ordinary white cement, this white cement has the characteristics of good fluidity and high whiteness.
②Mortar and concrete
Bentonite has good water absorption and water retention properties. Putting it into mortar can absorb the water in the mortar and act as a thickening water-retention material.
After adding organic matter to bentonite, a complexing reaction will occur to form a cross-linked polymer with bentonite particles as the main network points. The network structure of organic matter effectively limits the unlimited expansion of bentonite, and also limits the dry shrinkage of cement slurry, making the mortar and concrete structures more compact and tough, effectively preventing the seepage of water and the intrusion of harmful media.
4. Paint
①As an inorganic thickener
Since montmorillonite has a negative charge, when bentonite is dispersed in the paint, it will attract the polar groups in the paint to form a bentonite-organic complex. When the organic molecules enter the interlayer structure of the montmorillonite, the bentonite will expand, which can make the paint The consistency increases.
②As an auxiliary adhesive
Bentonite has good adhesion and hiding power. When put into paint, it can enhance the adhesion of the paint. It can also replace part of the base material, reduce costs, and be recycled.