ADVANTAGES OF MORTAR WITH REDISPERSABLE LADDER POWDER


Release time:

2020-03-09

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Polymer in the mortar as a second binder and inorganic binder cement complement each other, the two kinds of cementitious material system, namely cement and redispersible polymer powder to play their respective advantages, so that the performance of the mortar is very good complementary, so that the bonding performance of the mortar is improved.

Adding redispersible polymer powder mortar has the following advantages:

1 Good bonding properties for different substrates

Polymer in the mortar as a second binder and inorganic binder cement complement each other, the two kinds of cementitious material system, namely cement and redispersible polymer powder to play their respective advantages, so that the performance of the mortar is very good complementary, so that the bonding performance of the mortar is improved. Redispersible polymer powder to improve the bonding properties of mortar may have the following reasons:
① The polymer forms a polymer membrane with high bonding force between the cement paste and the aggregate, and blocks the pores in the mortar. Cement hydration and polymer film formation are carried out at the same time, and finally the interpenetrating network structure of cement paste and polymer film is formed.
② The polymer with reactive groups may chemically react with the silicate on the surface of solid calcium hydroxide to improve the bonding between cement hydration products and aggregates, thereby improving the bonding properties of mortar and different substrates.
The weakest link in the mortar is the interface between the mortar and the cement paste, and this area becomes the transition zone. The transition zone is a special area where shrinkage cracks form and cause the loss of bonding concrete force. If the mortar is subjected to stress, cracks are most likely to occur in the transition zone. Adding redispersible polymer powder in the mortar, the polymer film formed on the surface of the mortar particles forms a bridge between the mortar and the matrix, so that the interface between the mortar and the cement paste microcracks are reduced, so that the shrinkage cracks can be healed, thereby improving the bond strength of the mortar. Moreover, the tensile strength of the polymer film is more than 10 times greater than that of the ordinary mortar.

2 make the fresh mortar has good water retention

The hydration process of cement is a relatively slow process. If cement cannot be in contact with water for a long time, cement will not be able to continue to hydrate, thus affecting the development of later strength. John Schultz simulated the typical situation of the western wall in summer and used 10mm thick dry-mixed mortar to repair the mortar on the concrete slab. The test showed that the mortar without polymer powder modification failed, while the polymer modified mortar showed higher strength than the 28d standard. The reason was that the polymer powder improved the water retention capacity and increased the later strength of the cement. On the other hand, a small polymer phase was formed in the mortar, improved bond strength.

3 to improve the construction of fresh mortar and easy performance

After adding redispersible latex powder to dry-mixed mortar, the workability of the mortar is well improved, mainly because of the following reasons:
① When redispersible latex powder is mixed with mortar, since the redispersible latex powder particles are coated with water-soluble protective colloid, the coating layer can prevent irreversible coalescence between polymer particles and cause lubricating effect between particles. The polymer particles can be uniformly dispersed in cement paste. These dispersed particles can make the components of mortar flow separately like "balls" to improve the workability of mortar.
The redispersible latex powder itself has a certain air-entraining effect, and the induced effect of the redispersible latex powder on the air gives the mortar compressibility, so that the mortar has a good construction workability. In addition, the presence of tiny bubbles also plays a rolling bearing role in the mixture so that the workability of the mixture is improved.

4 Redispersible emulsion powder to improve the flexibility and crack resistance of mortar

After adding redispersible latex powder in the mortar, the compression ratio and tension-compression ratio of the mortar are greatly improved, which shows that the brittleness of the mortar is greatly reduced and the toughness is greatly improved, so that the crack resistance of the mortar is improved. The re-dispersed latex powder loses water in the mortar to form a film, which not only fills the defects and pores in the cement stone, but also makes the cement hydration products and the aggregate glue each other to form an interpenetrating network of polymers. Because the elastic modulus of the polymer film is lower than that of the mortar, the brittleness of the mortar is reduced. The flexibility of the mortar increases the maximum deformation limit of the mortar when it is destroyed, and it can absorb the energy required for defects and microcracks to the maximum extent, so that the mortar can withstand greater stress before it is destroyed. In addition, the polymer membrane has a self-stretching mechanism, and the polymer membrane has the function of a movable joint in the rigid skeleton formed in the mortar after cement hydration, which can ensure the elasticity and toughness of the rigid skeleton. The surface of the polymer film formed on the surface of the mortar particles has pores, and the surface of the pores is filled with mortar, which reduces the stress concentration and relaxes without destruction under the action of external force. The existence of high flexibility and high elasticity polymer areas also improves the flexibility and elasticity of the mortar.

5 Improve the wear resistance and impermeability of mortar

Latex powder has a certain air-entraining effect. If the amount of latex powder is large, the bubbles in the mortar will be excessive, and the tiny bubbles will be connected with each other to become large bubbles, thus overflowing the mortar body and reducing the air content of the mortar. Therefore, the dry apparent density of the mortar increased with the increase of the amount of latex powder, and the modified mortar has certain wear resistance and impermeability. The wear resistance of mortar is particularly important for ground materials, and it is an important performance of self leveling floor materials.
























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