RU2167114C2 - Method of preparing binder - Google Patents

Abstract

FIELD: building materials industry, more particularly manufacture of concrete and reinforced concrete structures, water-development works, bridges, road and aerodrome coatings or other products intended for service under severe climatic and aggressive conditions. SUBSTANCE: in method of preparing binder by combined grinding of cement, water-reducing additive, out surfactant and mineral additive is carried out in two stages, first to specific surface of 2800-4000 sq. cm/g and then to specific surface of 4000-8000 sq. cm/g; in 2nd grinding stage, structurizing additive is introduced, ratios of components being ground are as follows; wt.%: cement, 18.0-96.5; water-reducing surfactant, 0.5-7.8; mineral additive, 3.0-75.0; structurizing additive, 0.001-0.200, water-reducing surfactant includes sodium salt of naphthalenesulfoacid-formaldehyde condensation product, and structurizing additive includes phytosterine production by- product and/or ethylhydride sesquioxane. EFFECT: more efficient preparation method. 4 cl, 2 tbl

Description

 The invention relates to building materials and can be used for the production of concrete and reinforced concrete structures of hydraulic structures, bridges, foundations, road and airfield coatings and other products intended for use in harsh climatic and aggressive conditions.

 Highly effective water-reducing surface-active substances (surfactants), introduced into cement compositions as additives of superplasticizers, at optimal dosages (0.5-0.8 wt.% Of cement consumption) can reduce mixing water consumption by 20-25% while maintaining a given consistency of concrete mixtures and increase the strength of concrete by 1.3-1.45 times [1].

 The action of such additives is associated with the adsorption of their polymer molecules on the surface of hydrating cement particles. This leads to the release of water immobilized in cement flocs (structural cells), a decrease in the coefficient of internal friction of the cement-water system, smoothing of the microrelief of the surface of hydrated cement, as well as an increase in the forces of electrostatic repulsion of particles due to their "recharging" by adsorbed superplasticizer molecules.

A known method of preparation of a binder by co-grinding cement, water-reducing surface-active substances, mineral additives to a specific surface of 3000 cm ² / g [2].

 The last of these methods is the closest of the analogues.

 The problem solved by the invention is to develop a method for producing a binder, the concrete on the basis of which has a sharply increased frost and frost resistance, high strength and other physical and technical characteristics due to a significant limitation of water demand.

To solve the problem in the method of preparation of a binder by co-grinding cement, water-reducing surfactant and mineral additives, grinding is carried out in two stages: first to a specific surface of 2500-4000 cm ² / g, and then to a specific surface of 4000-8000 cm ² / g, moreover, at the second stage of grinding, a structuring additive is additionally introduced in the following ratio of ground components, wt.%: cement - 18.0-96.5; water-reducing surfactant - 0.5-7.8; mineral additive - 3.0-75.0; a structuring additive is 0.001-0.200, wherein the sodium salt of the condensation product of naphthalene sulfonic acid with formaldehyde is introduced as a water-reducing surfactant, and a by-product of the production of phytosterol and / or ethylhydridesexyvioxane is introduced as a structuring additive. In the process of two-stage intensive mechanochemical processing in the grinding device, the particles of the dry mixture are exposed to a large number of shock pulses that are repeated with a high frequency and have a different direction.

The consequence of an increase in the dispersion of the binder (up to S _beats = 4000-8000 cm ² / g) as compared to that generally accepted for cement (S _beats = 2500-3000 cm ² / g) and an increase in the modification of the active surfaces of cement particles and mineral additives by polymer molecules of a superplasticizer is the formation of diffusion barriers for spending water on wetting the developed surface of solid particles. The combination of previously incompatible properties — increased dispersion and low water demand (35–50% lower than that of traditional Portland cements) achieved by this leads to a maximum approximation of the solid phase, creation of conditions for diffusion interaction, a sharp increase in the cohesive strength of neoplasms, and minimization of large capillary pores and, ultimately, to obtain cement stone and composite materials based on it of high density and strength.

In addition to the noted phenomena, when a mechanochemical treatment is introduced into the binder in the second stage as a structuring additive, PGE - ethyl hydridesesquioxane (an organosilicon compound of hydrophobic-gas releasing action), hydrophobization of the binder particles additionally occurs, and hygroscopicity, caking and loss of activity during storage are reduced. After mixing the binder with water, PGE enters into a chemical reaction with lime formed during cement hydration and releases hydrogen, which forms a finely dispersed system of conditionally closed pores in concrete. In addition, the presence of an organic ethyl radical C ₂ H ₅ in the composition of the PGE molecule in the Si-R bond mosaicly hydrophobizes the walls of the pores and capillaries of the cement stone.

 As a result, the binder modified by the proposed method gives concrete not only increased strength and reduced water absorption, but also low diffusion permeability, in particular with respect to chloride ions, which makes its structure more resistant to frost-salt aggression.

 A comparative analysis of the known methods for the preparation of binders based on Portland cement used for the production of concrete and reinforced concrete structures showed that the substances introduced into the claimed solution are known (C-3, PPF, PGEN, silica fume, nepheline sludge). However, their application separately, as well as traditional dosages and methods of introducing mixing with water into concrete mixtures, do not provide concrete with the properties that they exhibit in the proposed solution, being components of a multifunctional modifier in the composition of the binder. In this case, there is a sharp decrease in capillary porosity, the formation of a finely dispersed zone of its contact with the aggregate, and, as a result, the non-additive effect of increasing the frost and frost resistance of concrete, accompanied by a significant increase in its strength and other physical and technical properties.

The method is as follows. Take Portland cement (or Portland cement clinker with 3-7 wt.% Gypsum), a mineral additive (nepheline sludge), a water-reducing surfactant (C-3 superplasticizer), place this mixture in a vibration mill (another grinding device) and subjected to mechanochemical treatment by co-grinding to the degree of dispersion, characterized by a specific surface S _beats = 2500-4000 cm ² / g according to Blaine.

Then, the resulting mixture was further added structuring additive (PPF and / or PGEN), mineral additive (microsilica - instead of or in addition to nepheline) and regrinding binder particles before reaching S _ud = 4000-8000 cm ² / g at the following component ratio, wt .%:
cement - 18.0-96.5
water-reducing surfactant - 0.5-7.8
mineral supplement - 3.0-75.0
structuring additive - 0.001-0,200.

 Superplasticizer C-3 is a sodium salt of the condensation product of naphthalenesulfonic acid with formaldehyde in the form of a water-soluble powder.

 Silica fume is a pulverized amorphous silicon dioxide, consisting of porous particles with a size of 0.01 ... 0.1 microns, a by-product of the production of crystalline silicon, ferroalloys and other silicides.

Nepheline (belite) sludge is a granular waste from alumina production, containing 80 ... 85% of the mineral Belite (β - CaO • SiO ₂ ), previously heat-treated at t = 400-500 ^o C.

 PPF air-entraining additive is a by-product of phytosterol production - enriched (purified) sulfate soap - in the form of a water-soluble paste-like concentrate.

 The hydrophobic-gas-generating additive PGE is an organosilicon compound - ethyl hydride sesquioxane - in the form of a water-soluble powder. On the basis of the binder prepared in this way, a fine-grained concrete mixture is prepared by mixing the binder with fine aggregate (quartz sand) and water for 5 minutes with a weight ratio of “binder: sand” = 1: 2. Water consumption is taken to ensure the required mobility of the concrete mixture, which determined on a shaking table according to GOST 310.4-81.

 The tests are carried out on prism samples 4x4x16 cm in size from fine-grained concrete made of equal-moving concrete mixtures (with a cone spread of 180-190 mm) with compaction in molds on a standard vibrating table for 6-10 sec. Part of the samples of each composition is molded with stainless steel benchmarks at the ends to measure residual deformations.

 The prepared samples were kept under normal-humid conditions for 28 days, after which one part of them was saturated with water for 4 days, the other part with a 5% aqueous NaCl solution. Then the control samples are tested for compressive and tensile strength in bending, they also determine the parameters of the pore structure of concrete.

 The integral (open) porosity of concrete is determined according to GOST 12730.3-78 by the volume of water absorption. The parameters of conditionally closed pores are determined by the linear method according to the polished sections of concrete using a microscope at a magnification of x75 in reflected light.

 Basic concrete samples are tested for frost and frost resistance as follows.

Accelerated frost resistance tests are carried out according to the modified method III GOST 10060-95 alternating freezing of samples in air at t = -50 ± 2 ^o C with thawing in water at t = 18 ± 2 ^o C.

Accelerated frost resistance tests are carried out according to the modified method GOST 10060-95 III by alternately freezing samples in stainless steel containers filled with 5% NaCI solution at t = -50 ± 2 ^o C with thawing in the same solution at t = 18 ± 2 ^o C.

 The kinetics of destructive processes in concrete samples is controlled by measurements of mass and relative residual deformations after every 8-10 freeze-thaw cycles. The critical values for evaluating frost resistance and frost resistance of concrete are: accumulation of 0.1% residual deformations and 3% weight loss by samples, respectively.

Example 1
The concrete mixture is prepared according to the invention. The binder composition includes, in addition to cement, only superplasticizer at a minimum level, the remaining additives are absent (Tables 1 and 2).

Example 2
The concrete mixture is prepared according to the invention. The composition of the binder includes, in addition to cement, only a minimum of the mineral supplement of silica fume (see Tables 1 and 2).

Example 3
The concrete mixture is prepared according to the invention. The composition of the binder includes, in addition to cement, only the minimum dosage of the structuring additive PPF (see tables. 1 and 2).

Example 4
The concrete mixture is prepared according to the invention. The binder contains superplasticizer, a mineral silica fume additive, and a PPF structuring additive in amounts below the declared dosages (see Tables 1 and 2).

Example 5
The concrete mixture is prepared according to the invention. The binder contains superplasticizer, a mineral additive of nepheline sludge and a structuring additive of PGE in amounts higher than the declared dosages (see tables 1 and 2).

Example 6
The concrete mixture is prepared according to the invention. The binder contains organic and mineral additives in optimal amounts close to the lower boundaries of the proposed interval (see tables. 1 and 2).

Example 7
The concrete mixture is prepared according to the invention. The binder contains organic and mineral additives in optimal dosages close to the upper limits of the proposed interval (see tables. 1 and 2).

Example 8
The concrete mixture is prepared according to the invention. The binder contains a multifunctional modifier, consisting of a full range of organic and mineral additives with a different ratio of components (see tables. 1 and 2).

 The compositions of binders by the present method are given in table. 1, and the composition of concrete and the results of their tests are given in table. 2.

Analysis of the test results showed that concrete samples based on a binder prepared by the present method (examples 8-10) with sharply reduced capillary porosity, characterized by the value of W ₀ , have a finely dispersed system of conditionally closed pores with optimal parameters.

The consequence of a comprehensive modification of the composition and structure of concrete is to increase its performance:
- frost resistance - up to 423-715 cycles of alternate freezing at -50 ^o C in air;
- frost resistance - up to 244-503 cycles of alternate freezing at -50 ^o C in a 5% solution of NaCl;
- compressive strength - up to 71.1 ... 82.6 MPa and bending - up to 13.5 ... 15.1 MPa at the age of 28 days of normal hardening.

Using the invention allows to increase the durability of concrete and reinforced concrete structures exposed to the combined effects of low negative temperatures, water and chloride salts, by increasing the frost and frost resistance of concrete to grades of frost resistance F 2000-5000 and more (in terms of standard freezing cycles at t = -18 ^o C according to the method of GOST 10060-95). Along with this, it is possible to save the clinker part of cement up to 75% by replacing it in the binder with mineral additives (industrial waste, for example, silica fume or nepheline sludge).

Sources of information
1. Babaev Sh.T., Komar A.A. Energy-saving technology for reinforced concrete structures made of high-strength concrete with chemical additives. - M .: Stroyizdat, 1987.

 2. RU 2023695 C1, publ. 11/30/1995.

Claims (3)

1. The method of preparation of a binder by co-grinding cement, water-reducing surfactant and mineral additives, characterized in that the grinding is carried out in two stages, first to a specific surface of 2500 cm ² / g, and then to a specific surface of 4000-8000 cm ² / g, and in the second stage of grinding, a structuring additive is additionally introduced in the following ratio of components, wt.%:
Cement - 18.0-96.5
Water-reducing surfactant - 0.5-7.8
Mineral supplement - 3.0-75.0
Structuring Additive - 0.001-0.200
2. The method according to p. 1, characterized in that the sodium salt of the condensation product of naphthalenesulfonic acid with formaldehyde is introduced as a water-reducing surfactant.  3. The method according to claim 1, characterized in that amorphous silicon dioxide and / or nepheline sludge are introduced as a mineral additive.  4. The method according to claim 1, characterized in that a by-product of the production of phytosterol and / or ethyl hydridesesquioxane is introduced as a structuring additive.

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