Dry-mixed mortar requires different types of admixtures with different mechanisms of action to match each other, and can only be prepared through a large number of tests. Compared with traditional concrete admixtures, dry-mixed mortar admixtures can only be used in powder form, and secondly, they are soluble in cold water, or gradually dissolve under the action of alkali to exert their due effect.
The main function of redispersible latex powder is to improve the water retention and stability of mortar. Although it can prevent mortar cracking (slow down the water evaporation rate) to a certain extent, it is generally not used as a means to improve mortar toughness, crack resistance and water resistance.
Adding polymer powder can improve the impermeability, toughness, crack resistance and impact resistance of mortar and concrete. The performance of redispersible latex powder is stable, and it has a good effect on improving the bonding strength of mortar, improving its toughness, deformability, crack resistance and impermeability. Adding hydrophobic latex powder can also greatly reduce the water absorption of the mortar (because of its hydrophobicity), make the mortar breathable and impervious to water, enhance its weather resistance, and improve its durability.
Compared with improving the flexural strength and bonding strength of mortar and reducing its brittleness, the effect of redispersible latex powder on improving the water retention and cohesion of mortar is limited. Since the addition of redispersible latex powder can disperse and cause a large amount of air-entrainment in the mortar mixture, its water-reducing effect is very obvious. Of course, due to the poor structure of the introduced air bubbles, the water reduction effect did not improve the strength. On the contrary, the strength of the mortar will gradually decrease with the increase of the redispersible latex powder content. Therefore, in the development of some mortars that need to consider the compressive and flexural strength, it is often necessary to add a defoamer at the same time in order to reduce the negative impact of latex powder on the compressive strength and flexural strength of the mortar.