Any additive that is helpful for foam retention, can improve foam stability and prolong foam life can be called foam stabilizer.As long as there is one or more of the following functions of the material, can be called concrete foam stabilizer:(2) can improve the viscosity of the foam system and the mechanical strength of the liquid film;(3) can increase the self-repair ability of liquid film;(4) can continue the liquid film drainage speed;(5) can make the foam become smaller and more uniform;（6）can make bubbles insoluble in water;（7）can improve the foam liquid film double electron layer arrangement density, increase the interaction between molecules.
1. Types of concrete foam stabilizer
Currently, there are several types of foam stabilizers commonly used:
（1）Categories: protein and protein stability bubble agent has good steady bubble effect, the reason is that they and van der Waals force between molecules of the foaming agent, and there are capable to generate hydrogen bond in the molecule of hydroxyl, carboxyl, amino, etc., these groups exist in foam system, can enhance the flexibility of bubble surface membrane and viscosity, so as to improve the mechanical strength of bubble surface film, have played an important role in stability of foam.
（2）Polymer compounds: this kind of foam stabilizer has a good water solubility, can prevent liquid membrane drainage, improve the viscosity of liquid phase, and can form high strength bubble film, so it has a good bubble stabilizer.
（3）Synthetic surfactants: six types of synthetic surfactants are mainly methanolamide, polyoxyethylene aliphatic alkyl alkyl amine, acetyldodecylamine, sodium n-acyl peptide, sodium n-alkyl thiotimide acetate and n-alpha dimethyl -N lauryl lysine.There are groups in their molecular structure that can form hydrogen bonds, which can improve the surface viscosity of foam liquid membrane.
Selection and application of foam stabilizer for foamed concrete
2.1 selection method of foam stabilizer for foamed concrete
Protein foam stabilizers can not only increase the elasticity of the foam membrane, but also increase the viscosity, so as to improve the mechanical strength of the foam membrane, so that it is not easy to break, and the cost of protein foam stabilizer is lower than other types of foam stabilizers.Macromolecular compound foam stabilizer mainly increases the viscosity of liquid film, and the effect of increasing elasticity is poor, so the mechanical strength of liquid film formed by it is slightly lower, but its effect of preventing liquid film from draining is better, and the overall effect of bubble stabilizer is better.Synthetic surfactant bubble stabilizers can improve the viscosity of liquid film, but their viscosity enhancement effect is not as good as the first two bubble stabilizers.However, most synthetic surfactant stabilizers have some foaming effect. Although the foaming effect is not very good, it is still beneficial to increase the amount of foaming.
Based on the above analysis, the optimal selection sequence of three kinds of foam stabilizers is as follows: protein, macromolecular compound and synthetic surfactant.
2.2 application method of foam stabilizer for foamed concrete
（1） Master the appropriate concentration and dosage: concentration and dosage are two important technical parameters of concrete foam stabilizer. Different concentrations of foam stabilizer should be added in different amounts.A certain concentration should have how much appropriate dosage, must be based on the different foaming agent varieties of performance and their own needs, some tests, through the test results to determine.
（2）Foam stabilizers should be used in combination: different types of foam stabilizers have different functions, and the use of foam stabilizers in combination can produce synergistic effects or complementary advantages.Composite stabilizing foam agent of bubble effect is superior to single component of foam agent, and the compound not only can be in the same class between the stability of foam agent, can also be between the different types of foam agent, such as between protein and protein compound, polymer composite between, between protein and polymer composite and composite between protein and synthetic surfactants, and so on.After designing the composite scheme, the experimental method should be used to verify the effect of the composite scheme, and the optimal choice should be made at last.
（3）Choose the appropriate way to add: there are two ways to add foam stabilizer to foamed concrete: one is to directly add foam stabilizer to the slurry.This method requires a large number of foam stabilizer, adding less effect is not obvious.This method is suitable for foam stabilizer with low price and increasing slurry suspension.The addition not only increases the stability of the foam, but also stabilizes the slurry and prevents the slurry from being stratified.Another method is to add the foam stabilizer into the foaming agent, so that the foam stabilizer and the foaming agent are mixed into one.This method has good adhesion increasing effect, the amount of foam stabilizer is generally less, and the foam stabilizer effect is better than the former one.
（4） Addition of synergistic agents: synergistic agents can significantly improve the bubble stabilizing effect of the bubble stabilizing agent, but it is a kind of synthetic surfactant, which has no bubble stabilizing effect.The addition of synergistic agent in small amount can improve the viscosity and toughness of foam and enhance the function of foam stabilizer.
（5）Preparation with activated water: the activated water can be sold on the market or made by the active water generator.Using activated water to allocate foamed concrete can improve the activity of foam stabilizer and promote the improvement of foam stability.
Foam stabilizers can improve the stability of the foam, but there are many types of foam stabilizers, the size of the role of various foam stabilizers is different, and the difference is large.Different foaming agents have different adaptability and requirements for foam stabilizer, and sometimes they need to be used together with other foam stabilizer measures.Accordingly, the action that stabilizes bubble agent cannot exaggerate also cannot look down upon, should treat scientifically.
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