**2. Method**

degree of cement hydration is considered. It is shown that the protein-based

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

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

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,

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

In addition, there are some ways of improving the stability of the foam based on

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 investi-

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

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

higher degree of polymerization results in the highly stable foams.

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

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 air-

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 affect-

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.

foaming agent is the best one [8].

*Foams - Emerging Technologies*

starch, and polysaccharides [10, 11].

other mechanisms of stabilization.

these particles around the foam films.

water layer of the foam film.

ing the stability of the foam.

**106**

gated. The positive effect obtained in this case is shown.

up to 90% [9].

cement-sand paste.

resins and latex [12].

stabilizing effect.

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 foam concrete and its products.

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 concrete and its products is described.

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

The stability of the foam was evaluated as the time of extraction (in minutes) of

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

Foam stability in the cement paste was evaluated by the coefficient of the foam resistance. Determination of the resistance coefficient was made by mixing equal volumes of cement paste and foam for 1 min followed by measuring the volume of the porous paste. The resistance coefficient of foam in the cement paste is calculated as the ratio of the volume of the porous paste to the sum of the volumes of the

The results of the studies are shown in **Figures 1**–**4**. From the figures it can be

seen that the stability of the foam stabilized with the SiO2 and Fe(OH)3 sols increases up to four times and the foam resistance coefficient in the cement

a half of the liquid phase from which the foam was prepared.

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

cement paste and foam (with water/cement ratio = 0.4).

**Figure 1.**

**Figure 2.**

**109**

*Stability of the foam stabilized with SiO2 sol.*

*Stability of the foam stabilized with Fe(OH)3 sol.*

### **Table 1.**

*The expected influence of sols of different nature on the quality of foam, foam concrete, and its products.*

and other geometric defects. They reduce the quality category of foam concrete products to category II (according to GOST 31360-2007).

To obtain the first quality category is important because in carrying out a brickwork, it allows to place the foam concrete blocks on the construction glue (coefficient of thermal conductivity, λ ≈ 0.3 W/(m∙°C)), and not on the cement mortar λ ≈ 0.3 W/(m∙°C)). The use of construction glue is proved to increase the thermal insulating properties of masonry walls significantly. It is assumed that the stabilized foam and the use of the hardening accelerator will considerably increase the number of products of the first quality category.
