The production process of foam concrete is actually not complicated, and the production equipment is simple. It can be cast on-site or mechanized in the factory. However, its performance is greatly affected by the foaming agent. Different foaming agents have different foaming properties, and the mechanical properties of foamed concrete prepared with different foaming agents vary greatly. How to prepare high-quality foam concrete, we must further compare the performance of the current mainstream blowing agent, determine the preparation of high-quality foam concrete foaming agent.
Definition of foaming agent for foam concrete
Foam concrete foaming agent belongs to a category of narrowly defined foaming agents, not all narrowly defined foaming agents. In the narrow sense of foaming agent, only a small part of it can be used for foam concrete. This is determined by the characteristics and technical requirements of foam concrete.
In industrial production and daily civilian use, the use of the blowing agent varies greatly, and different application fields have different technical requirements for the blowing agent. For example, the foaming agent for fire extinguishers particularly requires its instantaneous foaming capacity and oxygen barrier capacity but does not require its high stability and fineness. Another example is a flotation foaming agent for mining, which only requires it to have a strong adsorption force to the target substance and a good foaming force, but does not require high foaming multiples and foam stabilization. Blowing agents are currently used in almost all industrial fields and have a wide range of uses. The specific performance requirements for foaming agents in various industries are obviously different. The foaming agents that can be used in one industry may not be used or have poor effects in another industry. In the same way, the foam concrete foaming agent puts forward technical requirements for concrete foaming. In addition to its ability to generate foam, it pays special attention to the stability and fineness of foam and the adaptability of cement and other cementing materials. There are also few narrow-ranging blowing agents that can meet these requirements, and most blowing agents cannot be used in the actual production of foamed concrete. Therefore, the foam concrete foaming agent must be a few surfactants or surface-active substances that meet the above technical requirements.
Due to sufficient raw materials, the plant-type foaming agent in China has been produced and applied to a certain scale. Its main varieties are tea saponin and saponin. They are all nonionic surfactants.
①Tea saponin foaming agent, saponin, is a saponin extracted from the fruit of the Camellia plant. It is a natural nonionic surfactant with excellent properties.
② Saponin-type foaming agent Saponin-type foaming agent not only has better foaming power, but it is similar to tea saponin and has excellent foaming performance, and the foam reduction is uniform.
The foaming ability and stability of saponin are little affected by external conditions, and the requirements for the use conditions are not strict. First of all, its foaming power is hardly affected by water hardness, it can be used in a wide range of conditions of water hardness, but many synthetic anionic surfactants are easily restricted by water hardness, water hardness is slightly higher, Foaming power and foam stabilizing performance will be reduced. Secondly, saponin is not affected by pH.
Compared with the plant-type foaming agent, the performance of an animal-type foaming agent is roughly equivalent to that of plants, and the foam stability is stronger.
However, because its raw material resources are not as wide as plant type, the total production scale and application volume are not as good as plant type foaming agent.
The main disadvantage of animal-type blowing agents is higher cost, which is the fundamental reason why animal-type blowing agents are not as popular as synthetic ones.
Because the animal-type foaming agent is particularly stable, it is particularly suitable for the production of ultra-low density foam concrete, especially ultra-lightweight foam concrete and products with a density of 200 to 500 kg / m3. In general, foam concrete with a density above 600 is easier to produce, while density below 500 is difficult to produce, and density below 300 is more difficult to produce, and using an animal-type foaming agent is relatively easy to achieve Ultra-low density. Because even when the amount of cement is very small, and the amount of foam is extremely high, it is not easy to deform and collapse the mold, and the pouring stability is still very good. Its characteristics determine that it has a very broad application prospect despite its high cost.
In summary, although the above-mentioned foaming agents are widely used, they all have the disadvantages that the performance is not comprehensive enough to meet the actual foam concrete production needs. There is no one that can fully meet the foam performance technical requirements. This is reflected in the low foaming power and foam stability of rosin. Although the anionic surfactant has good foaming power and poor foam stability, the animal and vegetable protein foaming agent has good stability, but the foaming ability is average. This is an important reason why the overall level of blowing agents in China is low, and the quality is not high.
The only way to solve the poor performance of the above single-component foaming agent is to develop to the fourth generation of high-performance composite foaming agents and take the path of compound modification to produce a composite foaming agent.