RU2465252C1 - Method of producing foamed concrete - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to construction and can be used in making articles from foamed concrete. The method of producing foamed concrete involves preparation of a concrete mixture, adding a foaming agent - aluminium powder, ultrasonic treatment of the mixture, subsequent moulding and hardening. After preparation of the concrete mixture, resonator centres are formed therein in form of separate accumulations of fine particles, for which crude aluminium powder is added to the mixture and a low-speed mixing mode is set - blade rotational speed of 180 rpm. The mixture undergoes ultrasonic treatment, crude aluminium powder is added to the mixture and a high-speed mixing mode is set - blade rotational speed of 620 rpm. The invention is developed in subclaims.

EFFECT: obtaining foamed concrete articles with improved structural and mechanical properties.

4 cl, 1 ex, 3 dwg

Description

The invention relates to the field of construction and can be used in the manufacture of cellular concrete.

A known method of preparing a concrete mixture obtained by mixing cement, sand and a suspension of clay in water treated with ultrasound (RU No. 2371414. Concrete mixture. C04B 28/02, publ. 10.27.2009).

The disadvantage of this method is that the resulting product has a reduced strength due to the presence of the process of damping oscillations, leading to an uneven distribution of vibrations in the volume of the mixture, which reduces the efficiency of the method.

There is also a method of producing concrete by introducing uniformly dispersed dispersed fibers into the mixture (Rabinovich NF Composites based on dispersively reinforced concrete. Issues of theory and design, technology, designs: Monograph. - M.: Publishing house ASV, 2004. S .67-69).

The disadvantage of this method is that the fibers in concrete distributed in this way perform only the function of reinforcement and do not perform the function of amplifiers of superimposed ultrasonic vibrations, which reduces the efficiency of the method.

The closest technical solution to the proposed one is a method for producing aerated concrete by preparing a concrete mixture, introducing a blowing agent - aluminum powder, subsequent molding and hardening (Yu. M. Bazhenov. Concrete technology. Textbook. - M .: ASV, 2003. S .313-315).

The disadvantage of this method is that the resulting product has reduced crack resistance and open porosity in the form of channels, which reduces the quality of the products obtained by this method, and in general, reduces the efficiency of the method.

The objective of the present invention is to improve the quality of products from aerated concrete.

The technical result of the invention is to obtain aerated concrete products with improved structural and mechanical properties.

The task and the specified technical result is achieved by the fact that in the method of producing aerated concrete, according to the invention, after preparing the concrete mixture, resonator centers are formed in it in the form of separate clusters of particles of finely dispersed particles, for which a crude aluminum powder is introduced into the mixture and the low-speed mixing mode is set, they perform ultrasonic processing of the mixture, add purified aluminum powder to the mixture and set the intensive mixing mode — high-speed mixing. Resonator centers in the mixture are formed from coarse particles - aluminum sawdust. Coarse particles are simultaneously introduced into the concrete mixture - aluminum sawdust and fine particles of crude aluminum powder, they set the low-speed mixing mode, perform ultrasonic processing of the mixture, and then set the intensive mixing mode - high-speed mixing. After introducing the purified aluminum powder into the mixture and performing the mixing operation, repeated ultrasonic treatment of the mixture is carried out.

Using the low-speed mixing mode of the mixture with additional inclusions - dispersed particles leads to a violation of its structural homogeneity - to the formation of inhomogeneities in the form of separate clusters of particles - "hedgehogs".

The formation of resonator centers in the form of clusters of particles - "hedgehogs" allows you to increase the volume of propagation of vibrations in the mixture and increase the intensity of ultrasonic treatment of the zones around these clusters due to the concentration of energy of ultrasonic waves (vibrations) on the "hedgehogs", which, in General, increases the efficiency of the method.

The high-speed mixing mode is set, firstly, to break the "hedgehogs", and secondly, to achieve a uniform distribution of both unrefined aluminum powder particles and purified, in order to achieve maximum uniformity of the mixture.

Unrefined particles of aluminum powder will not be able to react and, accordingly, will remain inert particles. In this case, the particles of crude aluminum powder in the mixture perform two functions: they participate in the formation of resonator centers and participate in the formation of the skeleton as a dispersed fiber, performing the function of reinforcement.

The introduction of aluminum sawdust together with untreated aluminum powder due to its shape, approaching the shape of the fibers according to a higher value of the ratio l / d (l - length, d - diameter), allows to increase the efficiency of the formation of a cluster of particles - "hedgehogs" (N. Rabinovich Composites Based on Dispersion-Reinforced Concrete. Theory and Design Issues, Technology, Designs: Monograph. - M.: DIA Publishing House, 2004. - P.107).

The simultaneous introduction of coarse-dispersed aluminum particles into the raw material mixture — sawdust and unrefined aluminum powder particles, followed by setting the low-speed mixing mode and performing ultrasonic processing of the mixture, setting the intensive mixing mode — high-speed mixing allows, firstly, to enhance the effect of the formation of “hedgehogs” due to mutual braking coarsely dispersed (sawdust) and finely dispersed (powder) particles during mixing, and secondly, (increase) to enhance the resonator effect due to the formation of voids - pores in the "hedgehogs" from hydrogen gas bubbles generated during the reaction of aluminum powder, which, in general, accelerates the formation of a new mixture structure, the structural and mechanical properties of aerated concrete are improved, which increases the efficiency of the method.

Repeated ultrasonic treatment of the mixture allows accelerating the process of the chemical reaction to produce hydrogen gas, as well as preventing the effect of the formation of directional porosity - channels that are formed in the mixture when using conventional - vibration-free technology, which generally also increases the efficiency of the method.

The invention is illustrated by drawings, where in Fig.1 - the structure of the raw mix with inclusions of aluminum sawdust at low speed mixing; figure 2 - structure of the raw material mixture with inclusions of aluminum powder at high speed mixing mode; figure 3 - the structure of aerated concrete after hardening.

In figure 1, figure 3, the positions indicated:

1 - raw mix; 2 - particles of crude aluminum powder; 3 - accumulations of crude aluminum particles - “hedgehogs”; 4 - particles of refined aluminum powder; 5 - bubbles of hydrogen gas; 6 - form; 7 - cell pores.

The method is implemented as follows. Mortar mixture 1 is prepared, into which crude aluminum powder 2 is introduced and a low-speed mixing mode is set to obtain a heterogeneous structure — a structure with inclusions of accumulations of crude aluminum particles in the form of “hedgehogs” 3, after which ultrasonic processing is performed (Fig. 1). After ultrasonic treatment, purified aluminum powder 4 is introduced into the mixture and a high-speed mixing mode is set, while during the reaction of cement, powder and water gas-hydrogen is released in the form of bubbles 5 to obtain a new porous structure (Fig. 2). The resulting and processed mixture 1 is loaded into a mold 6 and left to harden under natural conditions or sent to a heat chamber, and a new highly porous structure is formed from cell-pores 7 (Fig. 3).

In the absence of a sufficient amount of unpurified aluminum powder 2, waste products are used - aluminum filings. They are introduced into the mortar mixture 1 together with untreated aluminum powder 2 with further sequentially performing all the operations described above.

To obtain a structure of increased strength after the operation for preparing the mortar mixture, coarsely dispersed aluminum particles are introduced into it at the same time - sawdust and untreated particles of aluminum powder 2, followed by setting the low-speed mixing mode and performing ultrasonic processing of the mixture. Then, operations are performed sequentially, according to the first embodiment.

To speed up the processes of structure formation, all the operations described in the first embodiment are performed, after which repeated ultrasonic treatment of the mixture is performed.

An example implementation of the method.

A mortar mixture is being prepared, for which 500 grade Portland cement is used in an amount of 0.22 kg, ground quartz sand in an amount of 0.236 kg, gypsum in an amount of 0.003 kg and water - 0.275 l. The preparation of the mixture is carried out in the mixer. Then, raw aluminum powder in the amount of 0.000535 kg is introduced into the mortar mixture and the mixture is mixed with a slow blade rotation speed of 180 rpm for two minutes to form separate clusters of aluminum particles - “hedgehogs”. After this, ultrasonic treatment of the mixture with an ultrasonic device "Retona" is performed for 10 minutes. Next, purified aluminum powder is introduced, a high-speed mixing mode is set - the rotation speed of the blades is 620 rpm. Then, the resulting and processed mixture is loaded into a mold to obtain cubes of 100 × 100 × 100 mm in size and transferred to a heat chamber. After hardening of concrete, the samples were tested in a press for uniaxial compression. The tests performed showed that the strength of concrete samples manufactured by the proposed method (specially treated with ultrasound) increased by 18% compared with untreated samples.

The tests performed proved the possibility of increasing the strength of concrete due to the targeted formation (distribution) of additional excitation zones and amplification of ultrasonic vibrations in the volume of the molded product, as well as due to the reinforcement of the concrete structure using specially treated and untreated aluminum particles, which proves the possibility of implementing the method of producing aerated concrete increased structural strength in the factory.

Claims (4)

1. The method of producing aerated concrete by preparing a concrete mixture, introducing a gas-forming agent - aluminum powder into it, performing ultrasonic treatment of the mixture, subsequent molding and hardening, characterized in that after the preparation of the concrete mixture resonant centers are formed in it in the form of separate clusters of particles of finely dispersed particles, why they add crude aluminum powder to the mixture and set the low-speed mixing mode — the blades rotate at 180 rpm, perform ultrasonic treatment of the mixture, introducing tons of purified aluminum powder into the mixture and an intensive mixing mode is set — high-speed mixing — blades rotational speed of 620 rpm. 2. The method according to claim 1, characterized in that the resonator centers in the mixture are additionally formed from coarse particles - aluminum sawdust. 3. The method according to claim 1, characterized in that coarsely dispersed particles — aluminum sawdust and finely dispersed particles of crude aluminum powder — are introduced into the concrete mixture, they set the low-speed mixing mode, perform ultrasonic processing of the mixture, and then set the intensive mixing mode — high-speed mixing. 4. The method according to claim 1, characterized in that after introducing purified aluminum powder into the mixture and performing the mixing operation, repeated ultrasonic treatment of the mixture is carried out.

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