Redispersible latex powder and cement are the main bonding and film-forming substances of water-resistant putty. The water-resistant principle is:
During the mixing process of redispersible latex powder and cement, the latex powder is continuously restored to the original emulsion form, and the latex particles are uniformly dispersed into the cement slurry. After the cement encounters water, the hydration reaction begins, the Ca(OH)2 solution is saturated and crystals are precipitated, and ettringite crystals and hydrated calcium silicate colloids are formed at the same time, and the latex particles are deposited on the gel and unhydrated. on cement particles.
With the progress of the hydration reaction, the hydration products continue to increase, and the latex particles gradually gather in the voids of inorganic materials such as cement, and form a tightly packed layer on the surface of the cement gel. Due to the gradual reduction of dry moisture, the redispersed latex particles tightly packed in the gel and voids aggregate to form a continuous film, forming a mixture with the cement paste interpenetrating matrix, and making the cement paste and other powder bone glued to each other. Because the latex particles coagulate and form a film in the interfacial transition area of cement and other powders, the interfacial transition area of the putty system is more dense, thus improving its water resistance.
At the same time, the active groups generated by the redispersible latex powder after redispersion, such as the functional monomer methacrylic acid introduced during the synthesis of the emulsion, contain carboxyl groups, which can cross-link with Ca2+, Al3+, etc. in the cement heavy calcium hydration product. , form a special bridge bond, improve the physical structure of the cement mortar hardened body, and enhance the compactness of the putty interface. The redispersed latex particles form a continuous and dense film in the voids of the putty system.
Post time: Nov-01-2022