Method of concrete mixture preparation

FIELD: construction.

SUBSTANCE: method of preparing the concrete mixture, consisting in mixing of cement, aggregates, water, and aqueous suspension of complex modifier of the following composition, wt %: silica fume 40-70; chemical additives 2-10; water - the rest, which is dried prior to mixing in the air stream to obtain powder consisting of granules, according to the invention, the aqueous suspension of complex modifier before mixing is subject to drying under the influence of continuous electromagnetic field of ultra-high frequency of 400-1000 MHz from microwave oscillators and heated air stream of microwave oscillator cooling to obtain powder with grains of size up to 500 microns and moisture of 9-12%; then the dried powdered complex modifier and cement are subjected to dispersion and disaggregation via exposure to pulsed electromagnetic field of ultra-high frequency of 1000-3000 MHz lasting 1-1.5 seconds, till the obtention of ultrafine powder of complex modifier with size of 60-100 nm, moisture of 1-8% and cement of size 0.1-5 microns, after that they are mixed, ground together and activated, form the disaggregated and activated mixture of cement and complex modifier, which is mixed with filler and water, concrete mixture is obtained; this mixture is subjected to the influence of powerful pulsed electromagnetic field of ultra-high frequency of 400-1000 MHz with duration of 1100÷nanoseconds.

EFFECT: increase of strength of concrete mixture.

1 tbl

 

The invention relates to methods for preparation of concrete mixtures with the addition of microsilica with chemical additives.

Known method of preparing a concrete mix with the introduction of its cement, aggregates, water and microsilica with chemical additives in the form of a single pasty product "pulp Alikram" [Woomin V.N., Alferov F.A., Lozovsky M.A. and other New additives in concrete technology - Pulp Alikram, Concrete and reinforced concrete, No. 2, 1990, p.40-41].

The disadvantages of the method are the tendency of the pulp to stratification, which requires periodic mixing during storage, exposure of the pulp to freezing at low temperatures, as well as the need for additional technological supply of superplasticizer and other additives. The plasticity of the concrete mixtures with the addition of such a paste-like product with time (15-20 min after preparation) drops significantly.

Known method of preparing a concrete mixture comprising mixing cement, aggregates, water and the aqueous suspension of the complex modifier containing silica fume and chemical additives, aqueous suspension of the complex modifier of the following composition, wt.%: fume 40-70, chemical additives 2-10, the rest is water, before mixing is subjected to drying in an air stream at 160-250°C to obtain a powder consisting of granules with a size of 500 μm and humidity 1-8%, the minimum time of mixing cement, aggregates, water and complex powder modifier is 3 min [RF Patent №2095327, C04B 28/00, publ. 10.11.1997, IB No. 31. Authors: Kaprielov S. and others, "Method of preparation of concrete mixtures"].

The disadvantage is not a high intensity strength and durability of concrete mixture to compression.

As noted by the authors, the use of integrated powder modifier concrete with a grain size of more than 500 μm (sample No. 8, table 1), while maintaining the ductility of concrete mixes after 120 min, leads to a decrease of concrete strength by 19% (7, table 2), which is obviously related to the insufficient degree of disaggregation is relatively large particles modifier.

It is known that, like all pozzolanic materials, silica fume reacts with calcium hydroxide Ca(OH)2released during the hydration of Portland cement in the formation of cementitious compounds. Very high purity and fineness of silica fume contributes to a more effective and rapid response. With proper dispersion thousands reactive spherical microparticles surround every grain of cement, sealing grout, filling the void solid hydration products and improving adhesion with placeholders.

In addition, in the process of mixing cement with water is prasouda flocculi - fine particles of cement are grouped into larger clumps.

Pore volume in floccular though quite large, but filled his water is still not enough to ensure full hydration of the adjacent grains of cement. Water in floccular fixed. The inflow from outside or outside practically stops. The situation is aggravated and what products started cement hydration even more clog internal channels.

In natural terms, this process results in the fact that the smallest and therefore the most reactive particles of cement, which were to provide fast curing huddle together in clumps - flocculi. They react with water mostly only on their outer surface. Inside the water reserves are being rapidly depleted, and the strength potential of the cement is tightly stored for a few years, or even decades, until the atmospheric moisture will not penetrate deep into these flocs.

If you look under a microscope, the grain structure of the cement particles, it can clearly be seen that he was being consolidated in the aquatic environment. Even it is rapid hardening cements with a predominance of particles less than 20 microns in the aquatic environment are aggregated into larger clumps - flocculi. The addition of completepicture S-3 is not completely removes this problem.

This method is selected in the image quality is as prototype.

The technical result of the proposed method is to increase the strength of the concrete mixture.

The technical result is achieved in that in the method of preparation of the concrete mixture, which consists in mixing cement, aggregates, water and the aqueous suspension of the complex modifier of the following composition, wt.%: fume 40-70; chemical additives 2-10; water - the rest, which, prior to mixing is subjected to drying in an air stream to obtain a powder consisting of granules according to the invention, the aqueous suspension of the complex modifier before mixing is subjected to drying by exposure to continuous electromagnetic field of ultrahigh frequency 400-1000 MHz microwave generators and hot air flow cooling of the microwave generators to obtain a powder with granules of a size of up to 500 microns and a moisture content of 9-12%, and then dried complex powder modifier and the cement is subjected to dispersion and disaggregation by exposure to a pulsed electromagnetic field ultra high frequency 1000-3000 MHz duration 1-1,5 seconds, to obtain ultrafine powder of the complex modifier size of 60-100 nm humidity 1-8% and cement in the range of 0.1-5 μm, after which they mix, grind together and activate, form of disaggregated and activated mixture of cement and is integral modifier, which is mixed with aggregate and water, receive the concrete mixture, which is affected by high-power pulsed electromagnetic field ultra high frequency 400-1000 MHz with a duration of 1÷100 nanoseconds.

Before mixing the concrete mix aqueous suspension of the complex modifier is subjected to drying by exposure to continuous electromagnetic field of ultrahigh frequency 915 MHz microwave generator and heated air flow cooling of the microwave generators to obtain a powder with granules of a size of up to 500 microns and a moisture content of 9-12%, this reduces energy needs and the duration of the technological process as heating and drying of the suspension takes place in the whole volume at once. Then dried complex powder modifier and the cement is subjected to dispersion and disaggregation by exposure to a pulsed electromagnetic field ultra high frequency 2450 MHz with a duration of 1-1,5 seconds, to obtain ultrafine powder of the complex modifier size of 60-100 nm humidity 1-8% and cement in the range of 0.1-5 μm. The pulse mode of the microwave generator provides a low energy consumption of the process.

Concrete strength will be increased due to the fineness (nanodispersed and ultradispersed) of the alloy particles and cement. The smaller the particles are, the faster and effective is e cement gains strength, forming a monolithic cement stone.

The mixing of the alloy particles and cement, their joint grinding and mechanical activation increases the activity of the particles in the interaction with water and other fillers. Received disaggregated and activated mixture of cement and complex modifier is mixed with aggregate and water, receive the concrete mixture, which is affected by high-power pulsed electromagnetic field ultra high frequency 400-1000 MHz with a duration of 1÷100 nanoseconds. This allows you to destroy the formed clots, which are obtained by the interaction of cement and water, modifier and water, cement modifier and water, which will speed up the process of curing and increase the strength of the concrete mixtures in compression.

An example implementation of the method of preparation of the concrete mixture.

Materials for preparation of complex modifier: microsilica (MK) brand MK-85 on THE 7-249533-90 "condensed silica Fume. Technical conditions"; a superplasticizer (SP) type C-3 on the basis of the sodium salt of the condensation product of naphthalenesulfonate and formaldehyde, corresponding to THE 6-36-0204229-625-90 "Plasticizer S-3"; nitrilotrimethylphosphonic acid (NTF), corresponding to THE 6-09-5283-86 "Nitrilotrimethylphosphonic acid. Technical conditions"; sodium nitrite (NN), corresponding to GOST 19906-74 "Nitritfrei technical. Technical conditions"; resin neutralized air (start), corresponding to THE 81-05-75-74. Suspension of complex modifier was subjected to drying by exposure to continuous electromagnetic field of ultrahigh frequency 915 MHz microwave generator and heated air flow cooling of the microwave generators to obtain a powder consisting of granules with a size of 500 microns and a moisture content of 9-12%. Dried complex powder modifier and the cement was subjected to dispersion and disaggregation by exposure to a pulsed electromagnetic field ultra high frequency 2450 MHz with a duration of 1-1,5 seconds, to obtain ultrafine powder of the complex modifier size of 60-100 nm humidity 1-8% and cement in the range of 0.1-5 μm, with further stirring, joint grinding and mechanical activation. Dispersion and joint grinding has led to an increase in interfacial surface section materials. Received disaggregated and activated mixture of cement and complex modifier mixed with aggregate and water, received a concrete mix. To this mixture was affected by high-power pulsed electromagnetic field ultra high frequency 915 MHz with a duration of 1÷100 nanoseconds.

Dispersion is the quality of thermodynamic characteristics of the system, defining Majesty is well the interface. Excess surface energy has a significant impact on the intensity and peculiarities not only chemical but also physical-chemical processes, both at normal and at elevated temperatures.

Characteristic dispersion is the degree of dispersion of S, i.e. the degree of atomization of the substance of the dispersed phase, representing the reciprocal of the particle size d.

The most convenient and common characteristic dispersion of the powdered materials is specific surface area, determined by the ratio of the surface of all particles to their volume or weight.

The value of specific surface area of the complex modifier was determined by the method based on the dependence of permeability of the layer of material from its dispersion. This method is based on measurement of the resistance offered to the air passivemode through a layer of a sealing material of a certain thickness and cross-sectional area.

Studies of the phase composition of the powder material and the determination of the particle size was conducted at the Center for collective use of scientific equipment "Study of physico-chemical properties of substances and materials" (MAC).

The proportion of particles with a size of 60-85 nm in a mixture of powdered inoculant was 70-85%. The average particle size of the modifier was 100 nm. Set the but with a scanning electron microscope JSM-6390A.

Considering the fact that bulk density modifier is 750±50 kg/m3the specific surface of the powder of the complex modifier amounted to 450,000 cm2/g, the specific surface of the powder cement - 36000 cm2/year

The freezing point of the obtained product was determined by visual assessment of the behavior of the material at low temperature: the change of flowability (angle of repose). When exceeding the angle of repose of 20° flowability was recognized as unsatisfactory. Accordingly, we determined the optimal range of humidity of the material, the freezing temperature and, accordingly, the angle of repose associated with relative humidity.

Optimal dispersion of the material was determined by the maximum strength of concrete, which was achieved by mixing the powder-like modifier with other components of the concrete mix for 3 minutes

Concrete mixes were prepared using Portland cement M400 (GOST 10178), quartz sand, with Μr=2,1 (GOST 8736), granite gravel fraction 5-20 mm (GOST 8267). In the method of preparation of the concrete mixture, taken as a prototype, in the mixer for at least 3 min mixed together: cement, aggregates, water and powdered product complex modifier multifunctional actions with a particle size in the range of 500 μm and a relative VL is the possibility 1-8%, which is prepared from the slurry by drying in an air stream at 160-250°C. In the proposed method, the silica fume and himebauch was introduced in the form of powder modifier, which is prepared from a suspension of complex modifier, by drying influencing continuous electromagnetic field of ultrahigh frequency 915 MHz microwave generator and heated air flow cooling of the microwave generators to obtain a powder consisting of granules with a size of 500 microns and a moisture content of 9-12%. Dried complex powder modifier and the cement was subjected to dispersion and disaggregation by exposure to a pulsed electromagnetic field ultra high frequency 2450 MHz with a duration of 1-1,5 seconds, to obtain ultrafine powder of the complex modifier size of 60-100 nm humidity 1-8% and cement in the range of 0.1-5 μm, with further stirring, joint grinding and mechanical activation.

Cement, silica fume and chemical additives belong to the class of imperfect dielectrics and extremely effectively interact with the microwave field. Absorbed by mixtures of microwave power is distributed approximately uniformly over the volume of the aggregated lumps that allows their fast heating. This leads to intense evaporation of water. When this humidity powdery material, the donkey processing, reaches 1-8%. This humidity is necessary to ensure the required conditions for grinding and mechanical activation, long-term storage, as well as to save pozzolanic activity and prevent clumping of the powder particles.

The concrete compositions with modifiers based on prototype and the proposed method was adopted the same, kg/m3:

cement 300; 730 sand; gravel 1120; water 165.

Powder modifier and suspension (slurry) was introduced into the concrete mixture at the rate of 15% microsilica by weight of cement, and water in the composition of the suspension was taken into account in the total amount of mixing water.

Concrete strength was evaluated by testing samples-cubes the size of the edge 10 cm, Tverdovsky under standard conditions.

In table 1, as an example, the results of tests of properties of complex modifier, concrete mixes and concrete, prepared by the proposed method.

It is known that the most active components of concrete is a mixture of cement and water. The speed and depth of hydration of the cement, the conditions of curing of concrete at an early age are critical factors, which affect the rate of curing of concrete, and on its quality.

Table 1
The components of the suspension and the influence of modifiers on concrete strength
№ p/pThe ratio of the components of the suspension, wt.%Humidity obtained modifier, %Freezing point modifier °CThe granule size, micronsThe strength of concrete 28 day standards. Chr., MPa
MKSP-3NTFNNStartWater
The placeholder
1505,50,16--44,341,3below -4047058,3
2505,00,16 4,34-401,1below -4050063,4
3505,50,16-0,0444,31,2below -4046054,2
4706,50,30--18,77,8-3150062,8
The proposed optionThe size of granules, nm
5505,50,16--44,341,5 below -409571,3
6505,00,164,34-402,1below -4010075,8
7505,50,16-0,0444,31,1below -409060,7

The effect of microwave heating is based on the absorption of electromagnetic energy in dielectrics. Field microwave penetrate to a considerable depth, which depends on material properties. Interacting with matter on an atomic and molecular level, these fields affect the motion of electrons, which leads to the conversion of microwave energy into heat at the same time throughout the volume on the depth of penetration of electromagnetic waves.

Such properties EMF microwave can intensify the strength of the concrete mix by 5-8%.

The table shows the test results of the properties of complex modifier,concrete mixes and concrete. The table shows that the samples No. 5-7, obtained by the proposed method, has a low moisture content and therefore a low freezing point. Efficacy was assessed on the concrete of the same composition.

The proposed method increases the strength of concrete of the same composition in 12-23% in comparison with the prototype.

The method of preparation of the concrete mixture, which consists in mixing cement, aggregates, water and the aqueous suspension of the complex modifier of the following composition, wt.%: fume 40-70; chemical additives 2-10; water - the rest, which, prior to mixing is subjected to drying in an air stream to obtain a powder consisting of granules, characterized in that the aqueous suspension of the complex modifier before mixing is subjected to drying by exposure to continuous electromagnetic field of ultrahigh frequency 400-1000 MHz microwave generators and hot air flow cooling of the microwave generators to obtain a powder with granules of a size of up to 500 microns and a moisture content of 9-12%, and then dried complex powder modifier and the cement is subjected to dispersion and disaggregation by exposure to a pulsed electromagnetic field ultra high frequency 1000-3000 MHz duration 1-1,5 seconds to obtain ultrafine powder of the complex modifier R is Merom 60-100 nm humidity 1-8% and cement in the range of 0.1-5 μm, then mix together ground and activate, form of disaggregated and activated mixture of cement and complex modifier, which is mixed with aggregate and water, receive the concrete mixture, which is affected by high-power pulsed electromagnetic field ultra high frequency 400-1000 MHz with a duration of 1÷100 nanoseconds.



 

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1 ex, 2 tbl

FIELD: chemistry.

SUBSTANCE: claimed invention relates to composition of binding agent based on sulfoaluminous clinker and Portland cement clinker and can be applied in industry of construction materials in production of concrete and building elements from concrete. Composition contains, at least, in wt %, relative to total composition weight: from 1 to 99% of Portland cement clinker or Portland cement and from 99 to 1% of belite-calcium-sulfoaluminous-ferrite clinker (BCSAF), which contains, at least, in wt %, with respect to total weight of BCSAF clinker: from 5 to 30% of phase of calcium aluminoferrite composition, corresponding to general formula C2AxF(1-x), with x in the range from 0.2 to 0.8, from 10 to 35% of phase of calcium sulfoaluminate "yelimite" C4A3S from 40 to 75% of belite (C2S), from 0.01 to 10% of one or several secondary phases, selected from calcium sulfates, sulfates of alkali metals, perovskite, gehlenite, free lime and periclase and/or glass-like phase, and total percent composition of said phases of which is higher or equals 97%. Invention also relates to concretes and building elements from it, obtained with application of claimed composition.

EFFECT: preservation or increase of strength, including early terms of hardening.

15 cl, 4 tbl

Cement additive // 2509739

FIELD: chemistry.

SUBSTANCE: invention relates to a cement composition based on belite, sulphoaluminate and calcium ferrite (BSCAF), BCSAF-containing clinker, having the following mineral composition relative to the total mass of the clinker: 5-30%, preferably 10-20%, of a phase based on calcium alumoferrite with general formula C2AxF(1-x), where X varies from 0.2 to 0.8; 10-35% of a phase based on calcium sulphoaluminate; 40-75% belite (C2S); 0.01-10% of one or more auxiliary phases, overall, selected from calcium sulphates, alkali metal sulphates, perovskite, calcium aluminates, gehlenite, free lime and periclase and/or a vitreous phase and alkanolamine, where the alkanolamine has said structural formula and is in amount of 0.01-1 wt %. The invention also relates to a method of producing a cement composition, which involves mixing BCSAF clinker with alkanolamine or adding alkanolamine to ground BCSAF clinker. The invention also relates to a suspension, cement mortar or concrete containing BCSAF and said cement composition. The invention is developed in subclaims.

EFFECT: high strength of BCSAF cement at later stages of hardening, including after 90 days.

10 cl, 3 ex, 3 tbl

FIELD: construction.

SUBSTANCE: granulated composite filler for concrete products of size 0.5-10.0 mm, consisting of core and shell, wherein the core is obtained by granulating the mixture together with diatomite and sodium hydroxide milled up to the specific surface area of 150-250 m2/kg at their weight ratio of 0.70-0.95:0.05-0.30 with bond by aqueous solution of sodium silicate with density of 1.2-1.3 g/cm3 in the amount of 0.1-7.0 wt % of mixture, and shell is formed on the surface of core by its balling with dry dust mixture together with milled quicklime and silicofluoride sodium in a weight ratio of 0.85-0.95:0.05-0.15 with the subsequent hardening up to the strength not less than 0.12 MPa, after the indicated balling the additional spraying of 40% aqueous solution of oxalic aldehyde in the amount of 1.0-8.0 wt % (per 100% substance) of weight of shell components is carried out. Concrete building product is obtained by using the granulated filler indicated above.

EFFECT: decrease of thermal conductivity and water resistance of concrete products when increasing and maintaining the strength characteristics.

2 cl, 1 tbl, 1 ex

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