CC BY
17
Mukhamedbaev Abdugafur Abduvaliyevich, master, doctoral student of Ph D., Tashkent Institute of Architecture and Civil Engineering
The Republic of Uzbekistan E-mail: mabdugofira@gmail.com
SLAG-ALKALINE FOAM CONCRETE BASED ON GRANULATED ELECTROTHERMOPHOSPHOR SLAG
Abstract: The article presents the results of research of grinding, physical and mechanical properties and the possibility of obtaining a slag-alkaline foam concrete on the basis of electrothermophosphor slag.
Keywords: slag-alkali binder, physical and mechanical characteristics, sodium disilicate, foaming agent, foam concrete.
Introduction
World consumption of fuel and energy resources is increasing at a rapid pace. This is due to several reasons, such as anincreasing of population, the need for comfortable housing, an increase in the amount and capacity of production, the development of transport logistics, etc. In parallel, the prices for these fuel and energy resources are also growing, which is included in the main expenditure side of the majority of production and the family budget.
The construction of new public and residential buildings using modern building materials and products is requirement of nowadays. More and more attention is paid to the use of insulation materials during construction.
It is generally known that thermal insulation materials are mineral wool, porous materials and other such kind of building structures. One of these artificially porous materials is foam concrete. At the moment, foam concrete is prepared and produced on the basis of a cement binder. Also, methods and technologies for manufacturing of foam concrete are well developed [1].
Analysis of modern scientific - technical and patent literatures (are) [2-5] showed that the issues of obtaining and studying the properties of foam concrete are developed mainly in the following areas:
- development and discovery of new types of foaming agents;
- development of new compositions of foam concrete;
- development of new methods and technologies for obtaining foam concrete;
- improvement of existing and development of new designs of technological equipment;
- development of new technological lines for foam concrete production;
- development of new methods for assessing technological parameters;
- etc.
All of the above listed works are conducted to obtain foam concrete on the basis of an ordinary cement binder [1-5]. To questions of reception of foam concretes on the basis of slag-alkaline binder are devoted a small amount of works [6; 7]. The reason for this is the high alkalinity value of the pH medium in comparison with the cement binder. High alkalinity of the pH medium interferes with obtaining stable foam, which after bursting the foam concrete solution into molds bursts and the porous structure breaks down.
The purpose of the work
In connection with this, the purpose of this paper is to investigate the possibility of obtaining slag-alkaline foam concrete.
Methods ofresearch and characteristics ofraw materials
As a solid constituent, granulated electrothermophos-phor (ETP) slag and sand were used. The alkaline solution of sodium disilicate (SDS) with a density of 1.3 g/cm3 was used as a quench liquid. As a foaming agent, "PB-2000" was chosen. Elemental composition of ETP slag is given in (Table 1).
Table 1. - composition of the ETP slag
Chemical elements,%
Si Al Ca Na K Fe Mg P Sr Mn Ti Cr Cu Zr
20 4 20 0.6 0.3 1 3 2 0.03 0.4 0.02 0.002 0.001 0.002
As can be seen from (Table 1), the ETP slag consists mainly of silicate calcium compounds.
In studies, we used well-known physical and mechanical methods of research, such as fineness of grinding, density, strength and electron microscopy.
The results of the research and their discussion
ETP slag was ground in a laboratory ball mill MBL-1. The results of grinding showed (Fig. 1) that the minimum required satisfactory degree of specific surface is achieved with a duration of at least 60 minutes [8]. It can be seen from the graph that in the interval 60-90 minutes there is a turning point in the grinding process.
Then coarsely and finely ground powders of ETP slag were closed with a solution of SDS with a density of 1,3 g/ cm3. Samples were formed in the form of cubes with a face size of 2 cm. The samples were hardened under air conditions up to 28 days old. The compressive strength of the samples was determined on a hydraulic press.
Figure 1. Change in specific surface area depending on the length of grinding
The results of compressive strength tests showed (Fig.2) increasing strength. As can be seen from the graph, the most
that the best results are obtained for fine-grained powders of intensive rate of compression strength is observed from 15 to
ETP slag with a grinding time of60-90 minutes (specific sur- 30 minutes of grinding in a ball mill (17.0-42.1 MPa), which
face 2972-3698 cm2/g) [9]. Grinding with duration of more is due to the broader granulometric composition of the binder
than 90 minutes does not give a positive effect in terms of leading to a denser packing of grains.
Specific surface, cm2 / g
Figure 2. Strength of slag-alkaline binder at 28-day age depending on the specific surface area
Previously, we conducted research on the effect of 4 foaming agents on the physical and mechanical properties of the slag-alkaline binder [10]. At the entrance to the research work, additional studies were also carried out to
determine the influence of the "PB-2000" foaming agent on the physico-mechanical properties of the slag-alkaline binder. The results of the study are given in (Table 2).
Table 2.- Effect of foaming agent on physico-mechanical properties of slag-alkaline binder
№ «PB-2000», (%) of the mass of ETF slag Storage conditions Compressive strength, MPa Density of samples, g/ cm3
7 days 28 days
1. - normally-moist 37.75 74.66 2.17
2. 0.4 23.08 41.00 1.98
3. 0.8 18.50 42.33 1.90
The results obtained determine the effect of the amount of foaming agent on the strength and density of the samples. It turned out that the foaming agent not only slows down the hardening processes, but also pores the structure of the slag-alkaline solution during the preparation process.
In the subsequent studies were carried out on the production of slag-alkaline foam concrete. For this, sand was used as filler. Samples were formed in the form of cubes with the dimensions of the face of 7 cm. The results of the investigations are given in (Table 3).
The results of the studies showed the possibility of obtaining a slag-alkali foam concrete on the basis of ETP slag. During the experiments, a more rapid destruction of the foam bubbles was found, leading to compaction of the foamed slag-alkaline solution. As a result, the density of the samples was high (1,03-1,17 g/cm3). To explain, it is possible with high alkalinity of the chosen system, leading to a rapid destruction of freshly molded bubbles of the entrained air.
Table 3. Physical and mechanical properties of slag alkaline foam concrete
№ Ratio of components, gr- SDS, ml PB-2000, ml Curing conditions Compression strength after28 days, MPa Density of the samples after 28 days, g / cm3
ETP slag Sand
1. 300 250 160 0.9 normally-moist 4.11 1.03
2. 1.8 5.55 1.17
Note: from 160 ml of SDS, 120 ml was used to prepare the solution and 40 ml of foaming foam
The microstructure of the slag-alkaline foam concrete was examined using an electronic optical microscope. On microphotographs of samples of slag-alkaline foam concrete (Fig. 3), clearly formed pores, cracks on the walls of pores and
partitions are visible. The resulting cracks in the form of a grid may have formed as a result of internal stresses during hardening. Perhaps for these reasons, the strength of the samples was 4.11-5.55 MPa.
a) with an increase of x 300 times b) with an increase of x 4000 times
Figure 3. Microphotographs of pore structure of slag alkaline foam concrete
Conclusions The best strengths of fine-grained powders were achieved in
During the research it was found that the minimum required time for grinding ETP slag is not less than 60 minutes.
fine-grained powders, by grinding for 60-90 minutes. It has been established that the amount of foaming agent "PB-2000"
has a negative influence on the physical and mechanical prop- a slag-alkali foam concrete with a strength of 4.11-5.55 MPa
erties of the slag-alkaline binder. It was also possible to obtain and a density of 1.03-1.17 g/cm3.
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