Foamed concrete is a new type of lightweight thermal insulation material which contains a large number of pores by foaming the foaming agent by mechanical means or compressed air method, then mixing and mixing with the cement mortar, and passing through the pumping agent or artificial cast-in-place construction.Foamed concrete is a porous building material with good thermal insulation and shock absorption properties. Due to its structural characteristics, foam concrete has the advantages of light weight, heat preservation, heat insulation, sound insulation, fire resistance and good seismic performance.
Physical foaming, that is, mechanical foaming, is introduced into the air by mechanical agitation or shearing, and air is encapsulated by an aqueous solution of a surfactant or a surface active material. The physical foaming process does not produce new substances for physical use, and the bubble diameter can be controlled by the shear rate. Physical foaming forms uniform and stable bubbles, and the type of blowing agent determines the quality of the foamed concrete. At present, physical foaming mainly utilizes an air compressor as an instrument to drive air into a foaming agent solution, a foaming agent solution into a foam, and then mixing the slurry and the foam to obtain a foamed concrete. Physical foaming can be used to adjust the properties of foam concrete by controlling the amount of blowing agent incorporated.
The principle of the compressed air method is mainly to use pressure to drive air into the foaming agent solution to form a foam.
At present, the commonly used physical foaming agents mainly include: resin soap foaming agent, vegetable protein foaming agent, petroleum sulfonic acid aluminum foaming agent, animal protein foaming agent, hydrolyzed blood gelling foaming agent, rosin acid soap foaming Agents, etc.
From the chemical composition point of view, physical foaming agents mainly include surfactants and proteins. The more polar groups in the surfactant structure contain hydrophilic groups, the stronger the hydrophilic action, and the better the bubble performance.
However, the surface layer of the foam has a large water content, which deteriorates the stability of the foam. At the same time, the surfactant can interact with the cement particles, hinder the hydration reaction and reduce the strength of the foam concrete.
The white matter-based foaming agent generates a small molecule by breaking the peptide bond, and increases the hydrophobic group to form an interface. In addition, hydrogen bonds are formed between the specific groups in the molecule, so that the solution forms a foam film with higher strength.
In addition, hydrogen bonds are formed between the specific groups in the molecule, so that the solution forms a foam film with higher strength.
The vegetable protein foaming agent is dissolved in water and is hardly affected by the hardness of water, and is non-toxic, odorless, and has a strong foaming ability, and the foam is fine and rich. However, the stability of the foamer product is poor, and the foam stabilization time is short and large-scale use cannot be achieved.