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Self-leveling mortar can freely flow to form a horizontal plane under its own weight with the help of certain equipment, overcoming the common quality problem of ordinary cement mortar, which is difficult to control the flatness of the ground and has good stability.

1. The hazards of bubbles produced by self-leveling mortar:

Under normal conditions, the prepared cement slurry-hardened body contains a large number of pores in its structure. Experiments have shown that pore structure is the most important factor affecting the strength properties of cement concrete materials. The presence of large amounts of air bubbles in cement slurry is harmful.

(1) A large number of bubbles will cause the density of the cement slurry to decrease and the strength of the hardened layer of the cement slurry to decrease.

(2) The overall volume of the cement slurry increases, and the bubbles generated are easy to burst, causing the volume to shrink and deform.

(3) When the cement slurry foams seriously, the foam gathers at the pump output port, forming an air cushion, causing the pump to run empty and hindering the construction.

2. Reasons for foams in cement-based self-leveling mortar:

Bubbles generally exist in two forms in cement slurry:

(1) One is that when the buoyancy force on the bubbles is greater than the blocking force of the cement slurry on the escape of the gas phase, the bubbles gather on the liquid surface to form continuous visible bubbles.

(2) The other is that when the viscosity and structural force of the cement slurry produce sufficient blocking effects on the escape of the gas phase, the bubbles are discontinuously dispersed inside the cement slurry, causing the cement slurry to increase in consistency and decrease in density during construction.

The existence of these two forms of bubbles has different effects on the mechanical behavior of ordinary cement slurry and will produce two different types of pores. One type is the inherent micropores in the gel-like hydration product. This type of pore has a size of about 2nm and does not cause cracks to form, but in sufficient numbers to reduce the elastic modulus and fracture energy. The other type is crack-like pores, with a maximum length of 1-3mm, which originate from the air bubbles brought in during casting and the accumulation of gaps between cement particles. Although this part of the macropore volume only accounts for 10% of the total pore volume, even under low stress, the critical crack value can be reached to cause fracture, which greatly limits the development of cement strength.

3. How to choose a defoaming agent:

Since there are currently not many defoaming agents specifically used for cement-based self-leveling mortar, the existing defoaming agents are mainly composed of several composite defoaming agents with defoaming and synergistic effects to comprehensively improve the defoaming efficiency. Due to the different chemical structures and properties of defoaming agents, different foam systems, foam suppression, foam breaking stability, foam breaking rate, etc. are different. When using defoaming agents in mortar, the defoaming agent must be chemically inert and not affect other properties of the mortar as much as possible. Therefore, the suitability of defoaming agents in mortars is very important.