Effect of defoamer on self-leveling compound
During the mixing of special mortar with water, the air introduced is wrapped in the wet mortar to form bubbles. At the same time, admixtures such as water-reducing agents, dispersible polymer powders and cellulose ethers have hydrophilic groups, which can reduce the surface tension of the liquid, cause bubbles to aggregate and increase the stability of the bubbles.
Generally, the optimum microbubble content in specialty mortars (such as self-leveling and waterproof mortars) is 3% to 6%. Uniform and stable small bubbles help improve the workability of the mortar and enhance its frost resistance and durability.
However, an increase in large bubbles will increase the void ratio of the mortar and reduce its mechanical properties. This is especially true for mortar products with waterproofing requirements, where foam suppression and defoaming are essential.
1. Effect on the wet density of mortar
Defoamers can inhibit the formation of bubbles and destroy existing bubbles in mortar. Therefore, adding defoamers to mortar products can reduce the gas content of the mortar and increase its wet density.
The effect of different types of defoamers varies, but within a certain range, the wet density of the mortar increases with the increase of the amount of defoamer added; when the amount of defoamer reaches a certain value, the wet density of the mortar tends to stabilize.
2. Effect on the fluidity of mortar
Defoamers can improve the initial fluidity of mortar, and the effect of different types of defoamers on fluidity varies. An effective defoamer not only quickly destroys bubbles, but also prevents them from regenerating for a long time.
3. Effect on the mechanical properties of mortar
Defoamers reduce the porosity of mortar and improve the pore structure of the cement paste by eliminating harmful air bubbles in the mortar, thereby increasing the compressive and flexural strength of the mortar, but not beyond a certain value.
