**4. Research of the foam concrete properties of various average densities on the basis of the stabilized foam**

Further the possibility of receiving heat-insulating non-autoclaved foam concrete of average density D200 on the basis of the foam stabilized with SiO2 sol was investigated.

For light thermal insulating non-autoclaved foam concrete, one of the significant problems is the reduction of the volume of the foam concrete mixture because of the mixture destruction, which results in the deviation from the projected average density and uneven structure of the material and exerts a negative influence on the properties of thermal insulating foam concrete.

It was assumed that a more stable foam will allow to avoid the destruction of the mixture, to provide the necessary density of the foam concrete, and to obtain a reduced thermal conductivity coefficient.

The composition of the foam concrete with medium density D200 is shown in **Table 4**. Portland cement CEM 42.5 was used as a binder, dolomitized limestone was used as a filler, protein foaming agent "Foamcem" was used as a foaming agent, and SiO2 sol of industrial production was used as a stabilizer (SITEC company).

To assess the stability of the foam concrete mixture, the volume instability of the foam concrete (mm) was measured at different contents of the dispersed phase of the sol in the foam. Volume instability was measured after 24 hours of the foam concrete hardening (**Figure 9**). From the figure it is seen that the use of the stabilized foam reduces the volume instability up to 0 when the concentration of the dispersed phase of sol in the foam is at least 0.2%. The coefficient of thermal conductivity of foam concrete of average density D200 at the design age was λ = 0.04 W/(m∙°C); for comparison, λair = 0.029 W/(m∙°C).

Further the physical-technical and thermal insulating properties of foam concrete and its products after the introduction of the stabilized foam into its composition were evaluated.

The compositions of the foam concrete mixtures of different average densities are shown in **Table 5**. During the preparation of foam concrete mixtures, 3% aqueous solution of foam on a protein basis stabilized with different sols was used. The samples were being solidified under normal conditions for 28 days.

During the experiment it was expected that a more stable foam will allow to use the electrolyte additives to activate the hardening of cement and to obtain the improved physical and mechanical characteristics of foam concrete and its products. In the case of using a conventional foam solution, such additives destroy the


**Table 4.**

*Consumption of the materials for 1 m<sup>3</sup> of foam concrete of average density D200.*

concerning the formation of hydrogenous and covalent chemical bonds in the

*Electron microscopy of the foam concrete samples of the medium density D600: (a) control sample and (b)*

Further, it was assumed that the appearance of chemical bonds and spatial stabilizing complexes should increase the thickness and strength of the foam film,

*IR spectra: No. 1, the system "aqueous solution of the protein foaming agent—Fe(OH)3 sol." No. 2, the system*

*Spatial stabilizing complexes formed by the introduction of various sols into the solution of protein foaming*

composition of the stabilizing silicon- and iron-protein complexes.

**Figure 6.**

**Figure 7.**

**Figure 8.**

**112**

*sample based on foam stabilized with SiO2 sol.*

*"aqueous solution of the protein foaming agent."*

*Foams - Emerging Technologies*

*agent: (a) silicon-protein complex and (b) iron-protein complex.*

foam. Sodium chloride (NaCl) in an amount of 5% by weight of cement was used as a hardening activator. The obtained characteristics of foam concrete are shown in **Table 6**.

When assessing the physical and mechanical characteristics of the foam concrete samples obtained on the basis of a stabilized foam, the following results were got:

*Frost resistance samples of the foam concrete of average density D600 prepared on the basis of the stabilized*

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

• The compressive strength of the samples with medium density D400–D600 at the age of 28 days of normal hardening increases up to 50% compared to the control sample, and the tensile strength at bending increases up to 69%.

• The thermal conductivity coefficient of the samples with additives decreases

Also, for samples of foam concrete of average density D600, a study of their frost resistance was carried out. It showed an increase in the class of frost resistance from

At the next stage of the work, physical and chemical studies of samples of foam concrete with medium density D500, prepared on the basis of stabilized foam and NaCl additives, were carried out: X-ray phase and differential thermal analysis. Three samples of foam concrete were studied: No. 1, control; No. 2, based on the foam stabilized with SiO2 sol and with the addition of NaCl; and No. 3, based on the

corresponding to β-SiO2 with d/n (interplanar spacing) = (3.337, 2.447, 2.280, 2.119, 1.657; 1.539) Å, as well as reflexes corresponding to Ca(OH)2, d/n = (3.114, 2.625, 1.926, 1.675) Å, low-basic hydrosilicate C6S6H d/n = (3.030, 2.033, 1.95) Å, and hydrosilicate C2SH2 (d/n = (3.030, 2.765, 1.830, 1.565) Å). In the X-ray spectra of samples No. 2 and No. 3, new lines belonging to the low-basic hydrosilicate C3S2H3 (d/n = 2.88; 2.766; 2.152; 1.973; 1.793; 1.627 Å) appear. The radiographs of samples No. 2 and No. 3 show the lines characterizing the dolomitized limestone. Alite analytical line (C3S, d/n = 1.76 Å) is present only in the control sample; in other samples, it does not manifest itself, which indicates a deeper degree of cement hydration in them. The formation of additional low-basic hydrosilicates with increased strength, as well as the absence of an analytical line of alite on the

radiographs, can explain the increase in the strength of foam concrete samples No. 2

The derivatographic analysis, **Table 8**, confirmed the data of X-ray phase analysis and showed that the total mass loss of samples based on the stabilized foam and

**5. Physicochemical studies of the composition of the obtained foam**

• The use of electrolytes does not destroy the stable foam.

**Stabilizer Class of frost resistance**

— F15 Sol SiO2 F35 Sol Fe(OH)3 F35 *All studies were conducted in accordance with GOST 25485-89.*

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

**Table 7.**

*foam.*

up to 16% in comparison with the control sample.

foam stabilized with Fe(OH)3 sol and with the addition of NaCl.

In all samples X-ray phase analysis showed the presence of reflexes

F15 to F35, as shown in **Table 7**.

and No. 3.

**115**

**concrete and its porous structure**

### **Figure 9.**

*Dependence of the volume instability of the foam concrete mixture on the content of the dispersed phase of SiO2 sol in the foaming agent solution.*


### **Table 5.**

*Consumption of materials per 1 m<sup>3</sup> of foam concrete of different average densities.*


### **Table 6.**

*Physical and mechanical characteristics of foam concrete samples of average density D400–D600 prepared on the basis of the stabilized foam.*

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


**Table 7.**

foam. Sodium chloride (NaCl) in an amount of 5% by weight of cement was used as a hardening activator. The obtained characteristics of foam concrete are shown in

*Dependence of the volume instability of the foam concrete mixture on the content of the dispersed phase of SiO2*

D400 330 50 152 2.1 1.5 6.1 D500 370 100 183 1.98 1.44 5.7 D600 400 170 211 1.75 1.3 5.0

> **strength, MPa/%**

D400 Control — 0.8/100 0.45/100 0.100/100

D500 Control — 1.3/100 0.69/100 0.120/100

D600 Control — 1.7/100 0.88/100 0.140/100

*Physical and mechanical characteristics of foam concrete samples of average density D400–D600 prepared on the*

Stabilized SiO2 sol 1.2/150 0.76/169 0.086/86

Stabilized SiO2 sol 1.9/146 1.14/165 0.101/84

Stabilized SiO2 sol 2.3/135 1.38/158 0.117/84

**Water (l)**

**Foaming agent (l)**

**Bending tensile strength, MPa/%**

1.2/150 0.66/147 0.09/90

1.7/131 0.88/128 0.107/89

2.2/129 1.15/131 0.132/94

**Stabilizer (l) SiO2 sol Fe(OH)3 sol**

> **Thermal conductivity, λ, W/(m∙°C)/%**

**Filler (kg)**

*Consumption of materials per 1 m<sup>3</sup> of foam concrete of different average densities.*

Fe(OH)3 sol

Fe(OH)3 sol

Fe(OH)3 sol

**Stabilizer Compressive**

**Table 6**.

*Foams - Emerging Technologies*

**Figure 9.**

**Table 5.**

**Table 6.**

**114**

*basis of the stabilized foam.*

**Class by average density**

**Foam type**

*sol in the foaming agent solution.*

**Cement (kg)**

**Class by average density**

*Frost resistance samples of the foam concrete of average density D600 prepared on the basis of the stabilized foam.*

When assessing the physical and mechanical characteristics of the foam concrete samples obtained on the basis of a stabilized foam, the following results were got:


Also, for samples of foam concrete of average density D600, a study of their frost resistance was carried out. It showed an increase in the class of frost resistance from F15 to F35, as shown in **Table 7**.
