The cement hydration process is a relatively slow process. If the cement cannot be in contact with water for a long time, the cement will not be able to continue to hydrate, thus affecting the later strength development. The strength of polymer-modified mortar is higher than the standard value because the redispersible polymer powder improves the water retention capacity and increases the strength of the cement in the later stage. Secondly, a fine polymer phase is formed in the mortar to improve the bonding strength.
After the redispersible polymer powder is added to the dry mixed mortar, the workability of the mortar is greatly improved. This is mainly due to the following reasons: A. When the redispersible polymer powder is mixed with the mortar, the redispersible polymer powder The solid particles are coated with water-soluble protective colloids. The coating can prevent irreversible agglomeration between polymer particles and provide lubrication between particles. The polymer particles can be evenly dispersed in the weight of the cement slurry. These dispersed particles The particles act like ball bearings, allowing the components of the mortar to flow separately and improve the fluidity of the mortar. Workability of mortar. B. The redispersible latex powder itself contains a certain air-entraining effect. The air-entraining effect of the redispersible latex powder should make the mortar compressible and make the mortar easy to construct. In addition, the presence of microbubbles also acts as rolling bearings in the mixture, thereby improving the workability of the mixture.
After the redispersible polymer powder is added to the mortar, the compression ratio and tensile ratio of the mortar are greatly increased, which indicates that the brittleness of the mortar is greatly reduced and the toughness is greatly improved, thereby improving the crack resistance of the mortar. The redispersible latex powder in the mortar dehydration film can not only fill the defects and pores of the cement stone, but also glue the cement hydration products with the aggregate to form a polymer interpenetrating network. Since the elastic modulus of the polymer film is smaller than that of the mortar, is low, so the brittleness of the mortar is reduced. The flexibility of the mortar increases the maximum deformation limit of the mortar when it fails, and the energy required for the expansion of defects and micro-cracks is absorbed in large quantities, allowing the mortar to withstand greater stress before failure. In addition, the polymer film contains a self-stretching mechanism. The polymer film forms a rigid skeleton in the cement hydrated mortar, which contains movable joints to ensure the elasticity and toughness of the rigid skeleton. The polymer film formed on the surface of the mortar particles has pores on the surface, and the pores are filled with mortar, which reduces stress concentration and relaxes without damage under the action of external forces. The presence of highly flexible, highly elastic polymer zones also increases the flexibility and elasticity of the mortar.