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Importance of adding redispersible polymer powder to gypsum self-leveling

Adding 2% to 3% of redispersible latex powder can significantly improve the wear resistance of self-leveling mortar, which can meet the 28d wear resistance ≤ 0.59 stipulated in the standard. The polymer disperses in the mortar and then forms a film, fills the pores of the slurry and interacts with the cement hydration products to form a three-dimensional network structure, which makes the mortar structure more compact. The flexible polymer film helps to relieve the internal stress of the mortar, reduces the stress concentration, and reduces the generation of micro-cracks, and this polymer film not only plays a hydrophobic role but also does not block the capillary, so that the material has good hydrophobicity and breathability. At the same time, due to the sealing effect caused by the polymer film, the material’s impermeability to moisture, chemical resistance, freeze-thaw resistance, and durability are greatly improved, and the bending strength, crack resistance, adhesion strength, and elasticity of the mortar are improved. And toughness, and finally can avoid shrinkage cracking of mortar.

Experiments have found that the initial fluidity of thick-layer gypsum-based self-leveling mortar increases first and then decreases with the increase in the amount of latex powder. The reason is that the latex powder has a certain viscosity in the dissolved water. The suspension ability of the slurry to the filler is improved, which is beneficial to the flow of the slurry; when the amount of latex powder continues to increase, the increase in the viscosity of the slurry leads to an increase in the viscosity of the slurry, and the fluidity shows a downward trend. The amount of latex powder has almost no effect on the 20-min fluidity of the mortar. As an organic binder, latex powder depends on the evaporation of water in the slurry, and the film forms a bond strength, and the gypsum base is self-leveling in the dry state. The water in the mortar evaporates, and the latex powder can form a continuous film, which has good cohesive force. The dry strength of the gypsum-based self-leveling mortar increases with the increase of the latex powder content. In the gypsum-based self-leveling mortar without latex powder, there are a large number of rod-shaped and columnar dihydrate gypsum crystals and irregular filler dihydrate gypsum crystals and between dihydrate gypsum crystals and fillers. Pile together to make the gypsum-based self-leveling mortar produce strength, and the gypsum-based self-leveling mortar mixed with redispersible latex powder, the latex powder forms a filamentary connection in the gypsum-based self-leveling mortar, and the dihydrate gypsum crystals and fillers, crystals An organic bridge is formed between the crystal and the dihydrate gypsum crystal, and an organic film is formed on the dihydrate gypsum crystal to wrap and connect the overlapping parts between the dihydrate gypsum crystals, thereby increasing the cohesion and cohesion of the gypsum-based self-leveling mortar and improving the The strength of gypsum-based self-leveling mortar The latex powder has film-forming properties in the mortar, which can improve the cohesion and bonding strength of the dry mortar. The formation of effective bonding between the fillers improves the cohesion between the dihydrate gypsum crystals and the fillers, thereby improving the bond strength of the gypsum-based self-leveling mortar macroscopically.

Post time: Apr-10-2023
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