**1. Introduction**

Under the stability of the foam, one understands its ability to maintain the dispersed composition, volume, and ability to prevent delamination. Foam stability is directly connected with the properties of liquid thin layers (foam films) which determine the structure of the foam. To evaluate quantitatively the stability of the foam, the rate of its destruction is determined [1].

Foaming agents used for the production of foam concrete of different hardening are considered in [2, 3]. The paper presents the classification of foaming agents according to their chemical characteristics [4, 5]. Properties of various foams, the bases of their obtaining, and destruction are investigated in the works [6, 7]. For foam concrete on the cement binder, the influence of the foaming agent used on the degree of cement hydration is considered. It is shown that the protein-based foaming agent is the best one [8].

Instability and destruction of the construction foam is one of the causes of volume instability in foam concrete. Especially sharply this question is on the lightweight foam concretes, because the volume of the foam in their composition is up to 90% [9].

In [21] the method of determining the coefficient of effectiveness and critical coverage as well as the coefficient of adsorption of particles on the interface of foam bubbles is considered. The possibility of obtaining the most stable foam is stated to

*The Improvement of the Quality of Construction Foam and Non-Autoclave Foam Concrete…*

The possibility of obtaining porous ceramics from a foamed suspension based on Al2O3–TiO2/ZrO2–SiO2 is discussed in [22]. Suspension particles have a stabilizing

The carried out analysis suggests that the increase in the stability of the foam is mainly due to the mechanism of "armoring" the surface of the foam bubble by the injected solid particles. This process prevents the liquid from leaking out of the foam film under the influence of gravity and so prevents its subsequent destruction. The mechanisms of foam chemical stabilization with the purpose of getting the

The use of additives based on SiO2 nanoparticles in modern construction is well

As the literature review shows, there is no knowledge concerning the methods of

One of the highly effective nano-additives used today is known to be silica (SiO2) sol [26–28]. Sols are colloidal aqueous solutions containing nanosize particles (1–100 nm) [29]. Chemistry of colloidal silica and its applications are discussed in

stabilization of construction foam on a protein basis for foam concrete at the expense of the introduction of sols of different nature into its composition. Also, the problems of improving the physical, mechanical, and thermal properties of the foam concrete of non-autoclaved hardening obtained on the basis of such a foam are

The main idea of the work is: it is possible to use SiO2 and Fe(OH)3 sols as stabilizers for protein foaming agent (PFA), as it is possible to form various chemical bonds between them, for example, hydrogenous, in the case of using SiO2 sol [30], or covalent, in the case of using Fe(OH)3 sol [12]. These bonds should contribute to the formation of strong spatial silicon- and iron-protein complexes which will increase the thickness of the foam film and prevent its destruction. This effect should preserve the volume of foam when it is introduced into the cement-sand mixture, as well as improve the physical, mechanical, and thermal characteristics of

The expected chemical bonds formed in the system "aqueous solution of protein foaming agent, sol of different nature," are shown in **Table 1**. The spatial stabilizing complexes based on them are also shown. The formation of these complexes is assumed to provide the foam stability increase. The expected influence of these effects on the physical and technical properties and quality of non-autoclaved foam

The foam stabilization effect can be important for the production of heatinsulating foam concrete of low density (class of average density ≤ D200), as it will prevent volume instability of raw foam concrete mixture. Also, this effect will make it possible to use hardening accelerators—electrolytes—in the composition of foam concrete which usually destroy it. In high-rise construction when the foam concrete

mixture is fed vertically to a great height, foam stabilization will prevent its destruction under the influence of its own pressure in the falling pipeline [12]. It is known that when getting foam concrete products by cutting technology, there appear problems with cutting the mass of foam concrete—there arise chips

effect and allow to obtain foam with air content up to 87%.

foam concrete are not considered yet.

*DOI: http://dx.doi.org/10.5772/intechopen.88234*

detail in literature and primarily in [30, 31].

depend on them.

known [23–25].

not considered.

foam concrete and its products.

concrete and its products is described.

**2. Method**

**107**

In this regard, one of the ways to improve the stability of the foam concrete mixture can be the stabilization of the construction foam introduced into the cement-sand paste.

At present there are various ways to improve the stability of foams based on various stabilization mechanisms. The use of additives (glycerin, methylcellulose, ethylene glycol) increases the viscosity of foaming agent solutions and slows down the liquid slug from foam films [10]. Also, for the stabilization of foams, it is possible to use substances that contribute to the formation of colloidal particles in films, preventing their dehydration. This group includes gelatin, joiner's glue, starch, and polysaccharides [10, 11].

For the production of thermal insulation materials, it is also recommended to use substances polymerized in the foam as stabilizers. Such additions strengthen the foam film significantly. They include polymer compositions based on synthetic resins and latex [12].

In addition, there are some ways of improving the stability of the foam based on other mechanisms of stabilization.

In [13] the influence of spherical monodisperse SiO2 particles with a diameter of 20 to 700 nm on the stabilization of foam based on sodium sulfonate was investigated. The positive effect obtained in this case is shown.

The question of obtaining stable foams formed from water dispersions of laponite modified by hexylamine is considered in [14]. It is shown that such a composition "surrounds" foam bubbles with a thin layer, providing a stabilizing effect.

It is also known that the foam can be stabilized by hydrophobic polymer particles with a diameter of less than 1 μm and a length of several tens of μm [15]. The stabilization effect is connected with the formation of dense thick layers of these particles around the foam films.

The paper [16] provides information that submicrometer-sized polystyrene particles in combination with poly[2–(diethylamino)ethyl methacrylate] of various degrees of polymerization—30, 60, and 90—can be used as stabilizers for foam. A higher degree of polymerization results in the highly stable foams.

It is also known that the use of hydrophilic silica particles and liquid paraffin in the foam increases its stability considerably [17]. It is shown that the stabilizing effect is connected with the adsorption of silica particles and oil droplets on the airwater layer of the foam film.

The publication [18] provides information that a significant increase in the stability of the foam can be achieved by the introduction of silica particles of the micrometer size. It is also proposed to use spherical silica particles with a diameter from 150 to 190 nm with their subsequent modification by silane substances [19]. It is established that the hydrophobicity of the surface achieved is a key factor affecting the stability of the foam.

In [20] the data confirming the fact that the stabilization of foams by solid particles is possible and results in a good effect are given. The result depends on the packaging of the particles on the surface of the foam films. The denser the packaging, the better the effect. Also, on the basis of calculations, it is shown that for stabilization of foams on the water basis and on the basis of the liquid, aluminum particles with a diameter less than 3 and 30 μm, respectively, are required.

*The Improvement of the Quality of Construction Foam and Non-Autoclave Foam Concrete… DOI: http://dx.doi.org/10.5772/intechopen.88234*

In [21] the method of determining the coefficient of effectiveness and critical coverage as well as the coefficient of adsorption of particles on the interface of foam bubbles is considered. The possibility of obtaining the most stable foam is stated to depend on them.

The possibility of obtaining porous ceramics from a foamed suspension based on Al2O3–TiO2/ZrO2–SiO2 is discussed in [22]. Suspension particles have a stabilizing effect and allow to obtain foam with air content up to 87%.

The carried out analysis suggests that the increase in the stability of the foam is mainly due to the mechanism of "armoring" the surface of the foam bubble by the injected solid particles. This process prevents the liquid from leaking out of the foam film under the influence of gravity and so prevents its subsequent destruction. The mechanisms of foam chemical stabilization with the purpose of getting the foam concrete are not considered yet.

The use of additives based on SiO2 nanoparticles in modern construction is well known [23–25].

One of the highly effective nano-additives used today is known to be silica (SiO2) sol [26–28]. Sols are colloidal aqueous solutions containing nanosize particles (1–100 nm) [29]. Chemistry of colloidal silica and its applications are discussed in detail in literature and primarily in [30, 31].

As the literature review shows, there is no knowledge concerning the methods of stabilization of construction foam on a protein basis for foam concrete at the expense of the introduction of sols of different nature into its composition. Also, the problems of improving the physical, mechanical, and thermal properties of the foam concrete of non-autoclaved hardening obtained on the basis of such a foam are not considered.
