1 Foaming technology
Prefabricated foams are widely used in the preparation of cellular concrete. Mechanical methods are used to obtain foams.
Two kinds of equipment, high-speed mixer and cement mixer, are used for making foam with high-speed mixer blade.Firstly, the foaming agent solution prepared according to a certain proportion is added to the high-speed mixer, and the precast foam is prepared under the rapid agitation of the blade.The resulting foam is then poured into a cement mixer to remove the ration.Finally, foam and slurry are mixed to make cellular concrete.The method of making foam with high-speed stirring blade is simple and reproducible, which can accurately reflect the foaming properties of foaming agent.However, due to uneven size of the upper and lower bubbles, a gauge is needed in the process of pouring the foam into the cement mixer, and the foam burst will inevitably occur, resulting in waste.
Compressed air foam method, which is mainly made of special foam cylinder this key equipment.The compressed air is mixed with the foaming agent solution in the special equipment, and the resulting foam is exhaled from the bubble cylinder through the compressed air. Finally, the produced foam is transferred to the cement mixer for mixing, and then the cellular concrete is made.Foamed tube internal materials available for use are magnetic disk, glass ball, copper and so on.
Combining with the using of foreign legal system of compressed air and the domestic high-speed stirring blades dip process, according to the characteristics of two different after comparison found that the legal system of compressed air foam equipment used, though a bit complicated, but the legal system of compressed air foam advantage is high speed mixing blade bubble method cannot reach, it effectively prevents the foam waste phenomenon.On the one hand, there is no uneven diameter of foam produced by compressed air after passing through the foam cylinder.On the other hand, the foam made is blown directly into the cement slurry, reducing the intermediate flow process;Moreover, slurry mixing and foaming are carried out simultaneously, so quantitative foaming can avoid the problem of excessive foaming.
2 Preparation technology
There are two methods of preparing cellular concrete: pre-foaming method and mixed foaming method.
The specific steps of pre-foaming method are as follows: firstly, foam is made by mixing foaming agent and water in a certain proportion, and then the corresponding raw materials are stirred evenly in the cement mixer to form slurry, and then the foams and materials are mixed evenly together and then poured into the template. Finally, maintenance and demoulding can be done after smoothing with low vibration.The preparation process used in this method includes four processes: foaming, stirring, foam mixing and molding.Foaming refers to the process of mixing foaming agent and water in the rapid agitation of foaming machine to produce a small foam with uniform diameter or the process of blowing the foam out of the bubble cylinder under the action of compressed air.Mixing is the process of mixing raw materials and water evenly in a cement mixer.Mixing, that is, the process of making foam and mixing even slurry in cement mixer.Molding, the process of transporting the slurry to the site for use or placement in the mold for maintenance.
The cellular concrete steps of mixed foaming method are: the base material is directly mixed with the surfactant, the surfactant plays its role in the slurry mixing process, followed by the emergence of foam, a large number of concrete cavity structure also gradually formed.Among them, the surface tension of foam can withstand the pressure of slurry on it, and the formation of a stable and solid skeleton after the initial coagulation of slurry produces pores.