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During the on-site mixing and mechanized construction of mortar, air is almost inevitably mixed in. According to on-site feedback, these visible or invisible tiny bubbles, if they remain stably inside the mortar in large quantities, will directly cause the hardened product to become loose and lack strength, and even the waterproof layer will lose its effectiveness. Common problems such as wall cracking and plaster cracking that occur frequently on construction sites often stem from these initially overlooked bubbles.

So here comes the question: Why does so much air get trapped during the mortar mixing process? This has to do with the raw materials. In actual production, we have found that –

In the mortar system, there are usually surfactant additives such as cellulose ethers, latex powder, and water reducers. These components not only improve the construction performance but also significantly reduce the surface tension of the liquid phase. As a result, once bubbles form, the liquid film becomes extremely stable and is difficult to rupture, making it even harder to be automatically expelled. A large number of bubbles are trapped inside the mortar, which is a very hidden but crucial quality defect in the mortar production process.

To break this deadlock, the most direct and effective approach is to introduce a dedicated defoamer. Industry data indicates that the mechanism of action of the defoamer is not complicated. The key lies in “breaking the membrane”. It can quickly penetrate into the foam liquid membrane structure, reducing the local surface elasticity of the liquid film, preventing it from maintaining a stable state. As tiny bubbles continue to merge, grow, and eventually rupture, the trapped air is released in an orderly manner, resulting in a significant decrease in the gas content of the mortar system and a steady increase in the wet density. The mortar becomes dense, which is the physical basis for all subsequent performance improvements.

What is more worthy of attention is the change in the strength system. After a reasonable blending of defoaming agents, the porosity decreases, the stress concentration points are reduced, and the strength naturally increases. The compressive strength and flexural strength of the mortar will both rise simultaneously. It should be emphasized that qualified defoaming agents will not interfere with the normal progress of the later cement hydration reaction. The hydration products can still grow uniformly, and the strength performance is more stable and longer-lasting than that of the non-defoaming system.

For first-line construction, the improvement brought by the defoamer is more obvious: the tensile bonding strength has significantly increased. When laying tiles on the wall or doing plastering and leveling, there are no longer many air holes between the mortar and the base layer. The bonding becomes denser, and the probability of cracking is greatly reduced. This conclusion is based on multiple on-site measurements – it is particularly obvious in mechanized thin-layer construction, and the feedback from the construction party is often “quick drying, strong adhesion, and less rework”.

In waterproof mortar, the role of defoamer is even more indispensable. After the internal pores are reduced, the capillary channels are cut off or effectively narrowed, resulting in a significant decrease in the water absorption rate of the mortar. In damp working conditions such as bathrooms, exterior walls, and basements, the anti-seepage and waterproofing ability is significantly enhanced. It can be said that in many waterproof mortar formulations, the defoamer is the key factor determining whether the project passes the backwater test.

Of course, controlling the dosage of the defoamer is also very important. The compatibility varies greatly in different systems. The viscosity grade of cellulose ethers, the film-forming properties of latex powder, and even changes in the aggregate grading can all affect the actual effectiveness of the defoamer. If the dosage is too low, the defoaming is not thorough; if it is too high, it may instead affect the fluidity and stratification degree of the slurry. Every time a formula adjustment is made, the optimal addition ratio must be determined through small-scale tests. This is not formal caution, but a necessary step to avoid batch quality problems in production caused by abnormal defoamers.

Overall, the improvement of the comprehensive performance of dry-mixed mortar by polyether-based defoamers forms a clear technical chain: reducing the air content; increasing the density; enhancing strength and adhesion; and reducing the risks of water absorption and seepage. Moreover, its benefits are not limited to a single indicator but extend throughout the entire engineering life cycle, from mixing, construction to long-term service, directly determining the quality of dry-mixed mortar.