RU2373163C1 - Cement of low water demand and method of its production - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: cement of low water demand contains Portland cement, mineral filler in the form of siliceous material and organic dewatering reagent. Additionally as mineral binder, carbonate-containing material is taken with share of calcium carbonate of at least 60% with ratio of carbonate-containing material and siliceous material of 5:95-95:5, besides components are taken with the following ratio, wt %: Portland cement 50-70; carbonate-containing material and siliceous material 30-50; organic dewatering reagent 0.3-3.0% of cement mass. Method for production of cement with low water demand comprises first joint grinding of Portland cement with organic dewatering reagent and siliceous material, and then their grinding with addition of carbonate-containing material.

EFFECT: reduced water demand of cement, increased strength.

2 cl, 2 tbl, 11 ex

Description

The invention relates to the technology of binders and can be used in the production of self-compacting, high-strength and high-quality concrete.

Known compositions of cements of low water demand, including non-additive Portland cement or Portland cement clinker with mineral siliceous additives (slag, ash, tuff, sand, etc.), with organic water-lowering reagents based on naphthalenesulfonic acid with formaldehyde, mineral active (granular blast furnace slag, granular blast furnace slag. ) and / or inert (silica sand, ore dressing tailings) fillers. There are also known methods for their manufacture, including joint grinding of these components (see Batrakov V.G. Modified Concretes. Theory and Practice. - Ed. 2nd, revised and supplemented. M: Stroyizdat, 1998, 768 pp., pg. 593-611).

The closest analogue to the claimed composition of cement of low water demand is the composition reflected in the description of the patent of Russia No. 2207995 "Method for the manufacture of cement of low water demand", IPC7 С04В 7/52, publ. 07/10/2003, according to which low water demand cement includes an alkali-containing Portland cement clinker with a calcium sulfate ingredient, a mineral siliceous filler, a modifier containing an organic water-lowering reagent, and 5-850 wt. Per 100 parts by weight of Portland cement are taken. parts of a siliceous mineral filler taken from the group: granulated blast furnace slag, fly ash, volcanic ash, pumice, tuff, quartz sand, feldspar sand, granite sowing, ore dressing tailings, cullet, brick fight, expanded clay or glass expanded dust and ., 0.6-2.5 wt. parts of an organic water-lowering reagent, taken from the group: alkali and / or alkaline earth metal salts of the product of condensation of naphthalene sulfonic acid with formaldehyde or a condensation product of melamine-containing resins with formaldehyde, or complex salts of alkaline earth metals and sulfuric and / or nitric and / or acetic and / or acetic acids and low molecular weight saccharides with the number of carbon atoms 3-5.

The closest analogue to the method of manufacturing cement low water demand is the description of the patent of Russia No. 2207995 "Method for the manufacture of cement low water demand", MPK7 С04В 7/52, publ. 07/10/2003, according to which, by mechanochemical processing, the following ingredients are milled together: Portland cement clinker, calcium sulfate ingredient, a modifier with a hardening accelerator and an organic water-lowering reagent at a ratio of 100: (1-7) :( 0.6-2.5) wt. parts to a specific surface of 400-700 m ² / kg. As a Portland cement clinker, a granular product is used for calcining a cement raw material mixture containing calcined impurities of sulfates and alkali metal carbonates. Additionally, an active mineral filler per 100 wt. parts of clinker from 5 to 850 wt. parts, which are used as components from the group: granulated blast furnace slag, fuel slag, fly ash, volcanic ash, pumice, tuff, quartz sand, feldspar sand, granite seedings, ore dressing tailings, cullet, brick fight, expanded clay or glass ceramite dust.

The disadvantages of the prototype for the composition of cement and the method of its manufacture are increased water demand (normal density) of cement, insufficient rheological characteristics of cement systems, namely: high ultimate shear stress and a small spread of cement systems, as well as their low strength. This is explained by the use of siliceous mineral fillers in their composition, in which the proportion of silicon oxide exceeds 80%, which are characterized by high moisture capacity, which leads to an increase in the water demand of cement systems and a deterioration in their rheological characteristics. A solvation shell is formed on the surface of the solid phase of these components, consisting of adsorption-bound water, comparable in volume to the volume of the particle. In this case, the amount of free water, which determines the fluidity of cement systems, is reduced by an amount comparable to the volume of the mineral filler. Therefore, with an increase in the proportion of siliceous filler in cement, the required mobility of the concrete mixture is achieved at a higher water demand. With an increase in siliceous mineral filler to 70%, the normal density of the dough increases to 20.8%, and the water-reducing ability of the water-lowering reagent in cement of low water demand drops to 20%.

The objective of the invention is to obtain cement of low water demand by reducing adsorption-bound water on the surface of the solid phase of the mineral filler of this cement, which improves the rheological characteristics of concrete mixtures, increases the strength and density of the concrete structure from such cement.

The problem is solved by the composition of low water demand cement containing Portland cement, a mineral filler in the form of a siliceous material and an organic water-lowering reagent, in which, in contrast to the prototype, a carbonate-containing material with a calcium carbonate fraction of at least 60% is taken as a mineral filler, with a ratio of siliceous material and carbonate-containing material 5: 95-95: 5, while all components are taken in the following quantitative ratio, wt.%:

Portland cement 50-70 Carbonate and siliceous materials 30-50 Organic Water Reducing Reagent 0.3-3.0% by weight of cement of low water demand.

The lower surface energy of carbonate-containing materials in comparison with siliceous materials leads to less adsorption of water on their surface, the adsorption layer becomes thinner, and more water remains in a free state, a greater plasticization effect is provided.

When using carbonate-containing and siliceous materials as a mineral filler at a ratio of 5: 95-95: 5, in addition to enhancing the water-reducing ability, the problem of increasing the strength of concrete and the density of the structure of concrete made from such cement is additionally solved. This is ensured by the binding of calcium hydroxide Ca (OH) ₂ , released during the dissolution of cement silicate minerals by amorphized silica SiO ₂ siliceous mineral material with the formation of strong tobermorite-like crystalline hydrates of the form CSH (I), which ensures high concrete strength. In addition, the total porosity decreases, the density of cement stone in concrete increases with an increase in volume concentration and dispersion of finely ground siliceous material.

The problem is also solved by the method of producing cement of low water demand, in which Portland cement, a mineral filler in the form of a siliceous material and an organic water-lowering reagent are ground. The method according to the invention differs from the known one in that, in addition, a carbonate-containing material with a calcium carbonate fraction of at least 60% in a ratio of carbonate-containing material and siliceous material of 5: 95-95: 5 is taken as a mineral filler, first they grind Portland cement with an organic water-reducing agent and siliceous material, and then grinding them with the addition of carbonate-containing material, and the components are taken in the following ratio, wt.%:

Portland cement 50-70 Carbonate-containing material and siliceous material 30-50 Organic Water Reducing Reagent 0.3-3.0% by weight of cement of low water demand.

A different grinding order of the initial cement components is associated with a difference in the hardness of their particles. The Mohs hardness for Portland cement clinker is 5–6, for siliceous materials 6–6.5, and for carbonate-containing materials it does not exceed 3.5. Therefore, the carbonate-containing material when co-milled with Portland cement and siliceous material is crushed more strongly as a softer material. A weak grinding of Portland cement will lead to less formation of active cement grains, which are responsible for the high hydraulic activity of cement of low water demand and increased physical and mechanical characteristics of hardened concrete on such cement. Low grinding of siliceous material will worsen its pozzolanic activity with respect to calcium hydroxide released during the dissolution of Portland cement materials, which will also adversely affect the properties of hardened concrete on such cement. Proceeding from this, a separate grinding of the starting components is required, consisting of preliminary activation of Portland cement and siliceous material in the presence of a water-lowering reagent and subsequent grinding of the carbonate-containing material to obtain a specific cement surface of low water demand 400-700 m ² / kg. In addition, the advantage of separate grinding is its economic feasibility, consisting in reducing the load on the mill and the cost of machine time for grinding solid materials (Portland cement and siliceous material).

For the preparation of cement of low water demand used:

- Portland cement of grades ПЦ500Д0 GOST 10178-85, ПЦ400Д0;

- Portland cement clinker - a granular product of firing of a cement raw mix, which contains calcined impurities of sulphates and carbonates of alkali metals with calcium sulphate ingredient, taken in a ratio of 90: 10-97: 3. moreover, the calcium sulfate ingredient is a two-water gypsum or chemical gypsum, taken from the group of chemical gypsum: phosphogypsum, borogypsum, titanogypsum;

- carbonate-containing mineral material - limestone rock of the Serafim deposit of the Republic of Bashkortostan; chemical composition of the rock, wt.%: CaCO ₃ 78-94, MgCO ₃ 3-16, clay impurities 5.1-8.9, as well as limestone, marble, chalk, dolomitic limestone.

As an organic water-reducing reagent used materials from the group of salts of alkaline earth and / or alkali metals:

- the condensation product of naphthalenesulfonic acid with formaldehyde - superplasticizer S-3 TU 6-36-0204229-625;

- a condensation product of melamine-containing resins with formaldehyde;

- a product based on sulfonated aromatic waste from the organic synthesis industry TU 025739-008-39389126-02 (sodium salt of the condensation products of sulfonated waste from the production of phenol with formaldehyde containing SO ₃ groups in the benzene ring);

- a product based on modified polycarboxylate - Melflux 2651F hyperplasticizer manufactured by Degussa Constraction Polymers (SKW Trostberg, Germany).

The following were used as siliceous material:

- quartz sand GOST 8736-93 with the largest grain size of 1.25 mm;

- granulated blast furnace slag of the Orsk-Khalilovsk metallurgical plant of the following chemical composition, wt.%: SiO ₂ 37-39, Al ₂ O ₃ 10-11, CaO 34-40, MgO 7-8, FeO 0.5-0.7, S 0.5-0.6;

- silica fume MK-85 of the Chelyabinsk Metallurgical Plant with the following chemical composition, wt.%: SiO ₂ 85-90, CaO 0,3-0,68, K ₂ O + Na ₂ O 0,91-1,85, Al ₂ O ₃ 0.68-0.79, MgO 0.78-1.01, Fe ₂ O ₃ 0.44-0.69, C 0.6-0.9, S 0.2-0.3, losses after calcination 2.7-4.2.

Low water demand cement was prepared as follows.

Before the grinding procedure, the limestone rock and blast furnace granulated slag were first dried at a temperature of 105-110 ° C to constant weight and then crushed to obtain grains with a grain size of no more than 2.5 mm. Then, in a spring mill, joint grinding of Portland cement, siliceous mineral material and a water-reducing agent was carried out to a specific surface of 550 m ² / g. Next, carbonate-containing material was added to the mill, and Portland cement, a water-lowering reagent, and siliceous mineral material were milled together with a carbonate-containing material to a specific surface of 550 m ² / g.

Rheological characteristics were measured as follows.

The normal density (NG) of the cement paste was determined according to GOST 310.3.

The water-reducing effect ΔV _d ,%, calculated by the formula

ΔV _d = (NG _n- NG _k ) · 100% / NG _n ,

where NG _n and NG _k are normal densities of, respectively, cement paste prepared from Portland cement (composition 1 of Table 1), and cement paste prepared from cement of low water demand.

The rheological ability (RC) was evaluated by the minicylinder of the obtained cement paste with a water-cement ratio W / C = 0.3 according to the method developed at the Department of Concrete, Ceramics and Cementing Blends of Penza State University of Architecture and Construction (a modified Suttard viscometer with a diameter of d = 10 mm and height h = 40 mm) (see Bazhenov Yu.M., Demyanova BC, Kalashnikov V.I. Modified high-quality concrete. Scientific publication. - M.: Publishing House of the Association of Building Universities, 2006. - 368 pp.) change ve Ichin limiting shear stress τ ₀ according to the formula:

τ ₀ = hd ² ρ / kD ² ,

where τ ₀ is the ultimate shear stress of the cement paste, Pa;

h and d are respectively the height and diameter of the minicylinder, m;

ρ is the density of the cement paste, kg / m ³ ;

k = 2 - coefficient taking into account the redistribution of stresses in viscoplastic bodies;

D is the diameter of the spread of cement paste, m

The increase in rheological ability ΔР for cement paste was calculated by the formula:

ΔР = RCc / RCn,

where РЦк and РЦн are fuses of the cement test minicylinder made of Portland cement and cement of low water demand, respectively.

To determine the density of the cement paste of normal density used measuring cylinder with a volume of 10 cm ³ . The cylinder was weighed and filled with cement paste in three layers to a mark of 10 cm ³ . After laying each layer, the cylinder with cement paste was shaken and tapped on a hard base. Next, the cylinder with the cement paste was weighed again. The density of the cement paste in g / cm ^{3 was} determined by the following formula:

ρ _cm = (mm ₁ ) / V,

where ρ _cm is the density of the cement paste;

m is the mass of the graduated cylinder with cement paste, g;

m ₁ is the mass of the graduated cylinder without cement paste, g;

V is the capacity of the graduated cylinder.

The strength of the cement stone after 28 days was determined by compressing samples of 2 × 2 × 2 cm made of cement paste of normal density according to GOST 310.3-76. The hardening conditions of the samples are normal (humidity 100%, ambient temperature 22-24 ° C).

The compressive strength was determined according to GOST 310.4.

The invention is illustrated by examples of compositions of cements of low water demand, are shown in Table 1. Table 2 shows the characteristics of the compositions of cements of low water demand in accordance with Table 1.

Example 1 relates to the manufacture of conventional cement without mineral additives and an organic dewatering agent. They took Portland cement 100 wt.% And shut it with water to obtain normal concrete density concrete.

Example 2 relates to the preparation of cement of low water demand from Portland cement, 50 wt.%, Siliceous material in the form of silica sand, 50 wt.%, And organic water-lowering reagent C-3 superplasticizer. To obtain cement of low water demand, all the starting components were simultaneously loaded into a spring mill and they were milled together to a specific surface of 400-700 m ² / kg, which was controlled on a device for measuring the specific surface and mass-average particle size PSX-8A. After grinding, the finished cement was removed and shut with water until a test of normal density was obtained.

Examples 3-5, 9-11 relate to the preparation of cement of low water demand from Portland cement 50 wt.% And the same amount of mineral fillers from carbonate-containing limestone of the Serafimovsky deposit and siliceous material of various types, taken in the indicated range of their values, using an organic water-reducing reagent Superplasticizer C -3. First, Portland cement, С-3 superplasticizer, silica filler were loaded into the mill and they were milled together to a specific surface of 400-700 m ² / kg. Next, limestone was added to the mill and grinding of materials was carried out to obtain cement with a specific surface of 400-700 m ² / kg.

Examples 6, 7, 8 relate to the preparation of cement of low water demand according to the above procedure from Portland cement 70 wt.% And mineral fillers in an amount of 30 wt.% From carbonate-containing limestone of the Serafimovsky deposit and siliceous material of various types, taken in the indicated range of their values, using organic water-reducing reagent S-3 superplasticizer.

A comparison of the test results of the prototype and the proposed solution shows that the inventive cement of low water demand differs from the known one by increased characteristics in terms of water reducing effect by 1.2-34.6%, improved rheological characteristics - ΔР increases to 250%, and τ ₀ decreases to 3.3 Pa, high compressive strength of cement stone up to 165 MPa.

Table 1
Compositions of low water demand cements Composition and its number one 2 3 four 5 6 7 8 9 10 eleven Portland cement - PTs500DO, wt.% one hundred fifty fifty fifty fifty 70 70 70 fifty fifty fifty Silica-containing mineral material - quartz sand - fifty twenty - - 10 - - twenty twenty 45 - MK-85 - - - - 5 - - 5 - - - - Granulated blast furnace slag, wt.% - - - twenty - - 10 - - - - Carbonate mineral material - limestone rock - - thirty thirty 45 twenty twenty 25 thirty thirty 5 Serafimovsky field, wt.% Organic water-reducing reagent,% of the mass of CNV - superplasticizer C-3 - 0.3 2.0 2.0 2.0 2.0 2.0 2.0 0.3 3.0 2.0

table 2
Physico-mechanical and rheological characteristics of low water demand cementites Composition number one 2 3 four 5 6 7 8 9 10 eleven Physico-mechanical properties: Normal density of NG cement test,% 25,2 23.3 15.6 16.7 14.6 16,2 17.8 15.8 23.0 14.8 16.9 Water-reducing effect ΔV _d ,% - 7.5 38.1 33.7 42.1 35.7 29.4 37.3 8.7 41.3 32.9 The density of the cement paste ρ, g / l /% 2,135
/one hundred 2,140
/one hundred 2,219
/ 104 2,228 / 104 2,248
/ 105 2,230
/ 104 2,239
/ 105 2,268
/ 106 2,201
/ 103 2,229
/ 104 2,221
/ 104 The strength of the cement stone after 28 days, MPa 103 106 126 130 139 150 155 165 105 131 124 Rheological properties: Water cement ratio 0.226 0.226 0.226 0.226 0.226 0.236 0.236 0.236 0.226 0.226 0.226 RC minicylinder spread, mm 10 12 35 33 36 34 33 34 13 37 24 Ultimate shear stress, τ ₀ , Pa 42.7 29.7 3.4 3.6 3,5 3.9 4.1 3.9 26.0 3.3 7.7 Strengthening rheological ability, ΔP,% one hundred 120 350 330 360 340 330 340 135 370 240

Claims (2)

1. Cement of low water demand, containing Portland cement, a mineral filler in the form of a siliceous material and an organic water-lowering reagent, characterized in that, in addition, a carbonate-containing material with a calcium carbonate content of at least 60% is taken as a mineral filler, with a ratio of siliceous material and carbonate-containing material 5: 95-95: 5, with all components taken in the following ratio, wt.%:
Portland cement 50-70 Carbonate and siliceous materials 30-50 Organic Water Reducing Reagent 0.3-3.0% by weight of cement of low water demand 2. A method of producing cement of low water demand, in which Portland cement is milled, a mineral filler in the form of a siliceous material and an organic water-lowering reagent, characterized in that, in addition, a carbonate-containing material with a calcium carbonate fraction of at least 60% in the ratio of carbonate-containing material is taken and siliceous material 5: 95-95: 5, first carry out a joint grinding of Portland cement with an organic water-reducing reagent and siliceous m material, and then grinding them with the addition of carbonate-containing material, and the components are taken in the following ratio, wt.%:
Portland cement 50-70 Carbonate-containing material and siliceous material 30-50 Organic Water Reducing Reagent 0.3-3.0% by weight of cement of low water demand