What types of defoamers are used in mortar and concrete, and how is their quality assessed?

Defoamers used in concrete and mortar are primarily aimed at eliminating harmful large air bubbles generated during mixing, thereby improving the material's strength and surface quality. Regarding the types of defoamers and quality evaluation, here is an overview:

Main Types of Defoamers

Based on chemical composition and characteristics, defoamers commonly used in mortar and concrete are mainly classified into several categories:

Silicone-based defoamers: They offer high defoaming efficiency and good stability, making them widely used at present. However, some products may have a certain impact on the flowability of concrete.

Polyether-based defoamers: These have relatively little effect on the flowability of concrete and are particularly suitable for high-fluidity systems such as self-leveling concrete.

Mineral oil-based defoamers: They are relatively low in cost, but their defoaming effect is usually not as significant as the first two categories, and they are mostly used in projects with strict cost control.

Other types: In practical applications, there are also specialty defoamers such as star-shaped polymers and polyacrylates, used to meet more specific performance requirements.

Core Factors Determining Quality

The quality of a defoamer is ultimately reflected in its actual application performance and depends on the combined effect of multiple factors:

Defoaming and foam-suppression capability: A good defoamer must not only quickly break existing bubbles (bubble-breaking property) but also inhibit the generation of new bubbles over a long period (foam-suppression property). Practical studies have shown that different types of defoamers vary significantly in effectiveness, so selection should be based on the specific formulation.

Compatibility with the system: It is crucial whether the defoamer is compatible with materials such as cement and superplasticizers. Poor compatibility may lead to unsatisfactory defoaming performance and even affect the final strength of concrete. Some professional concrete admixture companies develop series of products to suit different application systems.

Precise dosage control: More dosage is not necessarily better. Studies have indicated that while an excessive amount of defoamer can eliminate some small-sized bubbles, it may actually increase the number of harmful large-sized bubbles. Therefore, finding the optimal dosage is key to maximizing its performance.

Product manufacturing process and formulation: The production process of the defoamer, such as the emulsification method and the type and amount of emulsifiers, directly affects its dispersibility in water and ultimate performance. For example, using ultrasonic-assisted emulsification and controlling the appropriate hydrophilic-lipophilic balance (HLB value) are critical factors in producing high-quality defoamers.

Long-term stability: A high-quality defoamer should maintain stable performance during storage and use, without stratification or failure over time.

Therefore, when selecting a defoamer for mortar and concrete, one should not focus solely on price. Instead, its overall performance should be evaluated through testing based on specific project requirements and the material system.