Redispersible latex powder is a commonly used organic gelling material, which can be re-dispersed evenly in water to form an emulsion after contact with water. Adding redispersible latex powder can improve the water retention performance of freshly mixed cement mortar, as well as the bonding performance, flexibility, impermeability and corrosion resistance of hardened cement mortar. The latex powder changes the consistency and slipperiness of the system in the wet mixing state, and the cohesion is improved by adding latex powder. After drying, it provides a smooth and dense surface layer with cohesive force, and improves the interface effect of sand, gravel and pores. , enriched into film at the interface, which makes the material more flexible, reduces the elastic modulus, absorbs the thermal deformation stress to a large extent, and has water resistance in the later stage, and the buffer temperature and material deformation are inconsistent.
The formation of a continuous polymer film is extremely important to the performance of polymer-modified cement mortars. During the setting and hardening process of cement paste, many cavities will be generated inside, which become the weak parts of cement paste. After the redispersible latex powder is added, the latex powder will immediately disperse into an emulsion when it meets water, and gather in the water-rich area (that is, in the cavity). As the cement paste sets and hardens, the movement of the polymer particles is increasingly restricted, and interfacial tension between water and air forces them to gradually align. When the polymer particles come into contact with each other, the network of water evaporates through the capillaries, and the polymer forms a continuous film around the cavity, strengthening these weak spots. At this time, the polymer film can not only play a hydrophobic role, but also not block the capillary, so that the material has good hydrophobicity and air permeability.
The cement mortar without polymer is very loosely linked together. On the contrary, the polymer modified cement mortar makes the whole mortar very tightly linked due to the existence of polymer film, thus obtaining better mechanical properties and weather resistance sex. In the latex powder modified cement mortar, the latex powder will increase the porosity of the cement paste, but reduce the porosity of the interface transition zone between the cement paste and the aggregate, resulting in the overall porosity of the mortar being basically unchanged. After the latex powder is formed into a film, it can better block the pores in the mortar, making the structure of the interface transition zone between the cement paste and the aggregate more dense, and the permeability resistance of the latex powder modified mortar is improved, and the ability to resist the erosion of harmful media is enhanced. It has a positive effect on improving the durability of mortar.
Post time: Mar-14-2023