RU2533564C1 - Method of obtaining of cement mixing liquid - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method comprises electrochemical treatment of mains water in three-chamber electrolysis unit with ion-selective membranes by alternating asymmetric current. Meanwhile the electrolysis unit anode is made from shungite. During the electrochemical treatment of water in the anode and in the anode chamber the ultrasonic oscillations are exited, the frequency of which exceeds the cavitation threshold frequency within a range from 20 kHz up to 100 kHz, and the intensity of the named ultrasonics is in the field of stable cavitation from 1.5 W/cm² up to 2,5 W/cm². Water treatment is stopped at achieving of density of particles of hydrated fullerene 10-3-10-4%.

EFFECT: improvement of frost resistance of concrete mix, increase of cement hydratation level and strength of cement stone in early periods of curing.

Description

The invention relates to the building materials industry, and in particular to methods of processing a mixing fluid for preparing a concrete mixture, and is aimed at increasing the degree of hydration of cement and the strength of cement stone.

A known method of producing a mixing liquid by adding nanoparticles (nanomodifier), in particular fullerene with a particle size of 20 to 200 nm, to achieve a concentration of fullerene in water of 10 ^-4 -10 ^-7 % [1].

The disadvantage of this method is that the preparation of fullerene nanoparticles is a laborious and expensive process. In the 90s of the last century, when fullerenes were just beginning to be used for practical purposes, the cost of fullerene was $ 10,000 per gram. A relatively rapid increase in the total number of plants for producing fullerenes and constant work to improve their cleaning methods led to a significant reduction in the cost of C ₆₀ over the past 17 years - from $ 10,000 to $ 10-15 per gram {2}, which brought to the line of their real industrial use. Nevertheless, the price of fullerene, despite its marked decline in recent years, remains still quite high. In addition, artificially produced fullerene nanoparticles are practically insoluble in water, which does not allow increasing their concentration in the mixing liquid, and this also limits the potential possibilities of the modified fluid. In the aforementioned analogue, there is a need to fill in each successive portion of the mixing liquid a certain weight (dose) of fullerene particles, which complicates its implementation.

A known method of water treatment in the technology of preparing a concrete mixture, when the water before mixing with other components is treated with direct electric current in a diaphragmless electrolyzer. In this case, water treatment is carried out at an anode current density on the electrodes of (0.1-2.0) 10 ² A / m ² , and the total area of the anodes refers to the total area of the cathodes as 1: (1.0-2.5). In addition, before treatment with direct electric current or after it, the water is additionally treated with a magnetic field of intensity (0.01-2.0) 10 ⁴ A / m [3].

The disadvantages of the method are its complexity and high energy intensity associated with the complex treatment of the mixing fluid with a constant electric current and a magnetic field.

There is also known a method of preparing a mixing fluid for a concrete mixture, which consists in introducing hardness salts into the water, after which the solution is subjected to hydromechanical treatment followed by treatment of the liquid in the electrolyzer with alternating electric current (U = 30-60 V, i = 0.01-0.025 A / cm ² ; f = 50-200 Hz), after which the liquid is treated with a magnetic field of 300-500 Oe [4].

The disadvantages of this method are its low technology, complexity and high energy intensity associated with the implementation of chemical, hydromechanical, electrochemical and magnetic effects on the mixing fluid.

A known method of producing concrete stone, including the electrochemical treatment of a mixing fluid in a three-chamber direct current electrolyzer. At the same time, a 1-3% solution of calcium chloride is fed into the middle chamber of the electrolyzer, and tap water is delivered to the outer chambers. The electrochemical process is carried out at a rectified voltage of 220 V. Cement is shut with a solution from the anode or cathode chamber. At the same time, the increase in the strength of cement stone is up to 45% at the age of 1 day and up to 58% at the age of 28 days compared with the strength of cement stone closed with tap water [5].

The disadvantages of this method [5] should be attributed to its low technology associated with the use of a mixing component of a chemical component during electrochemical treatment (1-3% CaCl ₂ solution) and with the use of a relatively high voltage, which makes the use of this method energy-intensive and unsafe. In addition, the increase in the strength of cement stone, especially in the early stages of hardening, is low and amounts to about 45%.

The closest in terms of the number of essential features and the achieved result is a method of producing cement mixing liquid, including electrochemical treatment of tap water in a three-chamber electrolyzer with ion-selective membranes, followed by the use of treated water to mix the cement; treated cement selected from the middle or cathodic water is used to mix the cement or anode chambers, moreover, the electrochemical treatment of water is carried out by alternating asymmetric current at voltage 40-50 V, a frequency of 500-600 Hz with a ratio of amplitudes of forward and reverse half-waves of current 1.6-1.7 [6].

The disadvantage of the prototype method is that the mixing fluid is not structured, which reduces the technological properties of the concrete mixture (low frost resistance of the concrete mixture, ductility, degree of cement hydration, formwork time, etc.), and the strength of the concrete stone obtained using the mixing fluid activated by the prototype method, is relatively low.

The basis of the invention is to increase the efficiency of the processed mixing fluid, while the technical result is to increase the degree of frost resistance of the concrete mixture, increase the hydration of cement and the strength of the cement stone in the early stages of hardening.

The problem is solved as follows. According to the claimed method, the mixing liquid (tap water) is treated in a three-chamber electrolyzer with ion-selective membranes with an alternating asymmetric current. The anode of the electrolyzer is made of schungite and during the electrochemical treatment of water in the anode and in the anode chamber, ultrasonic vibrations are excited, the frequency of which lies above the frequency of the cavitation threshold in the range from 20 kHz to 100 kHz, and the intensity of the mentioned ultrasound lies in the region of stable cavitation from 1 5 W / cm ² to 2.5 W / cm ² , the water treatment is stopped when the concentration of hydrated fullerene particles reaches 10 ^-3 -10 ^-4 % and is used for mixing cement. In this case, for mixing cement take solutions from the cathode, middle or from the anode chamber of the electrolyzer.

The total between the claimed method and the prototype is that the electrochemical treatment of the mixing liquid is carried out in a three-chamber electrolyzer with ion-selective membranes with an alternating asymmetric current, and water is taken as the mixing liquid from the middle, anode or cathode cells of the electrolyzer.

The difference of the proposed method from the prototype is that the electrochemical treatment of the mixing fluid is carried out in the electrolyzer, the anode of which is made of schungite, and during the electrochemical treatment of water in the anode and in the anode chamber, ultrasonic vibrations are excited, the frequency of which is higher than the frequency of the cavitation threshold in the range from 20 kHz to 100 kHz and the intensity of said ultrasound is in stable cavitation of 1.5 W / cm ² to 2.5 W / cm ^2, wherein the water treatment is stopped when the concentration of particulate g dratirovannogo fullerene 10 ^-3 -10 ^-4%, after which the activated water is used for mixing cement. Additionally, it should be noted that when implementing the proposed method, the introduction of chemical additives is not required, which successfully replaces hydrated fullerene particles that have passed from the anode into the water during its activation.

The analysis allows us to conclude that there is novelty and essential features of the proposed method.

The electrochemical treatment of tap water with asymmetric alternating current in a three-chamber electrolyzer with ion-selective membranes enhances the chemical activity of the liquid, that is, activates it. Cement mixing with electrochemically activated water affects the dissolution, hydration, and hydrolysis processes, which generally leads to an increase in the strength of cement stone, especially in the early stages of hardening. In the interelectrode space of the electrolyzer, under the action of an asymmetric alternating current, the orientation and directional movement of ions and water molecules to the electrodes occurs, conditions are created under which resonance effects appear in the double electric layer (DEL) on the plane of the electrodes. Structural changes that began at the interfacial boundary in the DES, due to the coherent motion of water molecules and hydrogen bonds, propagate deep into the liquid phase, orientational structures are formed in which, under the influence of weak electromagnetic fields, their symmetry can be spontaneously broken and further destroyed. Significantly increases the active properties of the mixing fluid that is in the anolyte fullerene. Shungite contains not just fullerenes, but hydrated fullerenes that can be extracted with water. Thus, a change in the supramolecular structure of water significantly increases its chemical activity and, as a result, affects the process of structure formation of cement stone, leading to an increase in its strength. A unique property of fullerenes is their ability to structure water. Artificial fullerenes dissolve in water with great difficulty. But, if they are dissolved, as is the case in shungite, a multilayer shell of correctly located water molecules, about ten molecular layers, is formed around each ball. This water, in other words, the hydration shell of the Fullerene molecule is structured water.

It is known that during electrolysis of water, the anode is destroyed and positively charged ions of its material (cations) pass from the anode through the anolyte and enter the cathode chamber through the membrane.

In the inventive method, shungite is used as an anode. The use of shungite as an anode is primarily possible due to its high electrical conductivity and its other physical characteristics, given below:

- density - 2.25-2.40 g / cm ³

- porosity - 0.5-5%

- compressive strength 100-150 MPa

- modulus of elasticity (E) - 0.31 × 10 ⁵ MPa

- electrical conductivity - (1-3) × 10 ³ S / m

- thermal conductivity - 3.8 W / m · k.

- the average value of the coefficient of thermal expansion in the temperature range 20-600 C - 12 × 10 ^-6 1 / deg.

In the inventive method, the fact is used that during the electrolysis of the anode, positively charged ions (cations) of the anode material are pulled out from the anode by an electric field, which are transferred to the cathode region by the action of the field, saturating the catholyte with these cations.

It should be noted that fullerenes obtained by artificial means are practically insoluble in water. Shungite is a stone of natural origin, and hydrated fullerenes that are part of it are capable of dissolving in water.

In the inventive method, the process of receipt of positive ions from the schungite anode is intensified using ultrasound.

By its physical nature, ultrasound is an elastic wave, and in this it does not differ from sound.

It is generally accepted that the ultrasonic range includes frequencies in the range from 20 kHz to 1 GHz. Frequencies ranging from 16 kHz to 20 kHz relate to audible sound.

Frequencies below 16 kHz are infrasound, and frequencies above 1 GHz are called hypersound.

The frequency range of ultrasound can be divided into three subregions:

low frequency ultrasound (2 × 10 ⁴ -10 ⁵ Hz) - ULF;

ultrasound of medium frequencies (10 ⁵ -10 ⁷ Hz) - USCH;

ultrasound of high frequencies (10 ⁷ -10 ⁹ Hz) - UHF.

In liquid media under the action of ultrasound, a specific physical process arises and proceeds - ultrasonic cavitation, which provides maximum energy effects on the shungite anode.

In the ultrasonic wave, during half-periods of rarefaction, cavitation bubbles arise that collapse sharply after transition to the high-pressure region, generating strong hydrodynamic disturbances in the water and in the pores of the schungite anode, which significantly enhances the effect of the formation of cations from the anode material (schungite).

Cavitation is carried out due to alternating waves of high and low pressure formed by high-frequency sound (ultrasound).

Ultrasonic cavitation is the main initiator of the physicochemical processes that occur in a liquid under the influence of ultrasound, in particular, the formation of cations from the anode material.

Cavitation phenomena in a given medium arise only when the ultrasound exceeds the cavitation threshold.

The cavitation threshold is the intensity of ultrasound, below which cavitation phenomena are not observed. The cavitation threshold depends on the parameters characterizing both ultrasound and the liquid itself.

For water and aqueous solutions, the cavitation thresholds increase with increasing ultrasound frequency and decreasing exposure time.

At frequencies above 20 kHz, the threshold for unstable cavitation is in the range from 0.3 W / cm ² to 1 W / cm ² .

A further increase in intensity to 1.5 W / cm ² leads to a violation of the linearity of the oscillations of the walls of the bubbles. The stage of stable cavitation begins. The range of intensities of stable cavitation lies in the range from 1.5 W / cm ² to 2.5 W / cm ² . The bubble itself becomes a source of ultrasound vibrations. On its surface there are waves, microcurrents, electric discharges.

An increase in ultrasound intensity beyond 2.5 W / cm ² again leads to the stage of unstable cavitation.

In the inventive method, the most efficient use of the range of intensities of stable cavitation lies in the region from 1.5 W / cm ² to 2.5 W / cm ² .

It is in this range of frequencies and powers of ultrasound that activated water, washing the surface of the anode and penetrating into its pores, contributes to the intensive destruction of the anode, the material of which enters the anolyte in the form of neutral particles and ions (cations) of hydrated fullerene.

Under the influence of ultrasound, the activated water is intensively mixed and penetrates into the schungite through the pores, which allows it to interact with the surface of the schungite. Due to ultrasound, the rate of destruction of shungite particles and the entry of fullerene nanoparticles contained in shungite into water significantly increase, which significantly increases the efficiency of the process of water activation.

The best hydration of shungite particles occurs in the range of stable cavitation that occurs at low frequencies. Therefore, it is best to activate the mixing fluid of concrete mixtures with low-frequency ultrasound. The choice of this frequency range is due to the following factors.

Firstly, the frequency of 20 kHz is taken as the lower limit of the occurrence of ultrasonic vibrations. At frequencies below 20 kHz, the region of audible sound is located and cavitation processes in this region are not observed.

Secondly, in the low-frequency region lying in the range from 20 kHz to 100 kHz, the range of ultrasound intensities in which stable cavitation is observed, as indicated above, lies in the region from 1.5 W / cm ² to 2.5 W / cm ² .

The frequency region lying above 100 kHz refers to the region of medium frequencies of ultrasound. In this frequency range, at a certain ultrasound intensity, the effect of a gushing of a jet of activated liquid may occur, which can cause undesirable effects in the preparation of concrete mixtures. In addition, to ensure stable cavitation in the mid-frequency region, more powerful ultrasound emitters are required than to create the region in the low-frequency range. This is due to the fact that the cavitation threshold increases with increasing frequency of ultrasound. The need to use more powerful emitters in the mid-frequency region compared to the power of emitters in the low-frequency region leads to a complication and more expensive construction of the water activator.

In the inventive method, it is most effective to use the range of intensities of stable cavitation, which lies in the region from 1.5 W / cm ² to 2.5 W / cm ² .

It is in this range of frequencies and powers of ultrasound that activated water, washing the surface of schungite and penetrating into its pores, contributes to its intensive destruction and fullerene nanoparticles enter the water in the form of neutral particles.

The concentration of fullerene particles in water when exposed to shungite and water in the anode chamber of the electrolyzer with ultrasound depends on the frequency, intensity of ultrasound and the time of exposure to ultrasound on the schungite anode and water in the anode chamber.

The experiments showed that the effect of ultrasound on water and shungite for 10-20 minutes leads to a concentration of fullerene nanoparticles in water in the range of 10 ^-3 -10 ^-4 %, which is sufficient to give the mixing fluid (activated water) properties, required for effective mixing of cement. These properties of the mixing fluid, which becomes structured, lead to an increase in the degree of hydration of cement and the strength of concrete stone, as well as to improve workability of the concrete mixture, to reduce the water-cement ratio, without compromising the quality and technological properties of concrete mixtures.

It is possible to form a judgment on how much water the fullerene can structure from the following considerations. Since the diameter of the hydration shell is ten times the diameter of the carbon sphere, its volume and, consequently, the mass of structured fullerene water will be proportional to the linear cube and will exceed the mass of fullerene by about a thousand times. Thus, fullerene structures thousands of times a large mass of water. In other words, that already hundredths of a percent of fullerene are able to structure a significant proportion of the solution. Those. fullerene when activated mixing liquid acts in small and ultra-small doses.

By its properties, structured water surrounding a fullerene molecule differs significantly from ordinary. In particular, it does not freeze at 0, but at -2.8 ° C. This significantly increases the frost resistance of the concrete mixture, which allows concreting at lower temperatures without additional heating of the concrete mixture.

Example. For the preparation of cement stone, Portland cement M 300 was used, as a mixing liquid, activated water prepared according to the prototype method and the claimed method. The cell was made three-chamber, flowing.

The middle chamber of the cell is formed by ion-selective membranes MK-40 and MA-40. The cathode with an area of 30 cm ² was made of stainless steel and in both cases (in the prototype and in the claimed method) remained the same. The anode in the cell changed. When processing water according to the prototype method, it was made of pressed graphite, and according to the claimed method - from shungite. The process of electrochemical treatment in both cases was carried out on an alternating asymmetric current (S = l, 6-1.7) at a voltage of 40-50 V, a frequency of 500-600 Hz. The difference was that during the treatment of water according to the claimed method, ultrasonic vibrations were excited in the anode and in the anode chamber, the frequency of which was higher than the frequency of the cavitation threshold in the range from 20 kHz to 100 kHz, and the intensity of the mentioned ultrasound lay in the region of stable cavitation from 1, 5 W / cm ² to 2.5 W / cm ² . In this example, the ultrasound frequency was 20 kHz, and the intensity of the mentioned ultrasound lay in the region of stable cavitation and amounted to 2 W / cm ² . An industrial sound processor “Hielscher Ultrasound Technology UP” of the UIP 1000 hd brand was used as a cavitation disintegrator [7].

It was experimentally established that when treating activated water for 10-20 minutes, the concentration of hydrated fullerene particles changed 10 ^-3 -10 ^-4 %, respectively. In this example, the water was treated in both cases for 20 minutes. This duration of the process guaranteed that the concentration of fullerene particles in the mixing liquid would be 10 ^-3 -10 ^-4 %. After 20 minutes, the water treatment was stopped, after which activated water was used to mix the cement.

Cement hydration was investigated by the X-ray diffraction method using a DRON-4 apparatus. Studies have shown that in the cement test prepared by the prototype method, the hydration of cement was 70%, while according to the claimed method, it was equal to 86%.

The cement was cemented with the obtained solutions (W / C: = 0.27) and cubes of 3 × 3 × 3 cm in size were formed, which solidified under naturally moist conditions. On time (7-28 days), the samples are tested for compressive strength. The compressive strength of a cement stone mixed with a mixing fluid prepared according to the prototype method was at the age of 7 and 28 days, on average, 242 and 427 kgf / cm ² , respectively, while the compressive strength of a cement stone mixed with a mixing fluid prepared by the inventive method , at the age of 7 and 28 days averaged 272 and 513 kgf / cm ^3, respectively.

Thus, the claimed method in comparison with the prototype method can increase the degree of hydration of cement by 1.23 times, and the strength of the cement stone in compression of 1.12 and 1.2 times at the age of 7 and 28 days, respectively. An additional advantage of the mixing fluid prepared by the present method over the prototype is that it does not freeze at 0, but at -2.8 ° C. This significantly increases the frost resistance of the concrete mixture, which allows concreting at lower temperatures without additional heating of the concrete mixture.

Information sources

1. Pukharenko Yu.V., Nikitin V.A., Letenko D.G. Nanostructuring of mixing water as a way to increase the effectiveness of plasticizers of concrete mixtures // Building materials. - Science, No. 8 (appendix to the scientific and technical journal "Building Materials", 2006.-. 154-161.

2. Vul A.Ya. Materials of electronic equipment, No. 3, p. 4 (1999).

3. Patent of the Russian Federation N 2017702, M. cl 5 C04B 40/00, bull. No. 15, 08/15/94.

4. USSR patent No. 1782230, M. class 5. С04В 40/00, Bull. N 46, 12/15/92.

5. Auto No. 1705266, M. kl5 С04В 40/00, Bull. No. 2, 01/15/92.

6. RF patent №2163582. A method of obtaining a cement mixing fluid Semenova GD; Sarkisov Yu.S.; Eremina A.N .; Semenov V.D .; SV samples. / -Published: 2001.02.27. Bull. No. 6 (Prototype).

7. Inquiry from http://www.hielscher.com.

Claims (1)

A method of obtaining a cement mixing liquid, including the electrochemical treatment of tap water in a three-chamber electrolytic cell with asymmetric alternating current ion membranes, followed by the use of treated water taken from the anode chamber, middle or cathode cement mixing chambers, characterized in that the anode of the cell is made of shungite and in During the electrochemical treatment of water in the anode and in the anode chamber, ultrasonic vibrations are excited, the frequency of which lies above the frequency threshold cavitation in the range from 20 kHz to 100 kHz and the intensity of said ultrasound is in stable cavitation of 1.5 W / cm ² to 2.5 W / cm ^2, the water treatment is stopped when the concentration of particles of hydrated fullerene 10 ^-3 -10 ^-4 %, after which activated water is used to mix cement.