RU2379240C1 - Cement of low water demand and method of making thereof - Google Patents

Abstract

FIELD: construction engineering.

SUBSTANCE: method for making cement of low water demand involves a combined grinding of Portland cement and an organic dewatering reagent to the specific surface 400-700 m²/kg and grinding thereof with a mineral carbonate-containing dust with calcium carbonate portion 60 wt % and more to said specific surface in the following ratio, wt %: Portland cement - 50-70, carbonate-containing dust - 30-50, the organic dewatering reagent - 0.3-3.0 over 100%. Cement of low water demand is made by the method described above.

EFFECT: additional reduction of water demand, higher density of the cement paste, durability of the cement stone, improved rheological characteristics.

2 cl, 2 tbl, 12 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., P. 593-611).

The closest analogue to the claimed composition of cement of low water demand is the composition reflected in the Description to the patent of Russia No. 2207995 "Method for the manufacture of cement of low water demand", MPK7 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 a description of the patent of Russia. No. 2207995 "Method for the manufacture of cement of 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 of calcination of a cement raw mix is used, which contains calcined impurities of sulphates and carbonates of alkali metals. 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, seeding from granite crushing, 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, insufficiently high rheological characteristics of cement systems, namely, high ultimate shear stress, 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 decreases to 20%.

The objective of the invention is to obtain cement of low water demand with reduced 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.

The problem is solved by the composition of cement of low water demand, containing Portland cement, mineral filler and an organic water-lowering reagent, the specific surface of which is 400-700 m ² / kg, which, unlike the prototype, is obtained by co-grinding Portland cement with an organic water-lowering reagent to the specified specific surface, and then their grinding with the addition of a mineral filler to the specified specific surface, moreover, carbonate-containing material with a fraction of ka was taken as a mineral filler Bonate calcium not less than 60% of the material in the following ratio, wt.%: Portland cement 50-70, 30-50 carbonate material, an organic water reduction agent 0.3-3.0% by weight of cement of low water demand in excess of 100%.

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.

The problem is also solved by the method of producing cement of low water demand, in which Portland cement, mineral filler and organic water-reducing reagent are ground to a specific surface of 400-700 m ² / kg. The method according to the invention differs from the known one in that a carbonate-containing material with a calcium carbonate fraction of at least 60% is taken as a mineral filler, first a joint grinding of Portland cement with an organic water-reducing reagent is carried out to a specific surface of 400-700 m ² / kg, and then grinding with by adding the specified carbonate-containing material to a specific surface of 400-700 m ² / kg, in the following ratio, wt.%: Portland cement 50-70, carbonate-containing material 30-50, organic water-reducing reagent 0.3-3.0% of cement mass of low water demand, in excess of 100%.

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, and for carbonate-containing materials it does not exceed 3.5. Therefore, the carbonate-containing material when co-milled with Portland cement 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. Proceeding from this, a separate grinding of the starting components is required, consisting in the preliminary activation of Portland cement in the presence of a water-lowering reagent and in the subsequent grinding of carbonate-containing material with them to obtain a specific surface of cement 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.

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 a cement raw material mixture containing calcined impurities of sulphates and carbonates of alkali metals with a calcium sulfate ingredient, taken in a ratio of 90: 10-97: 3, and 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 wastes of the organic synthesis industry TU 025739-008-39389126-02 (sodium salt of condensation products of sulfonated wastes from the production of phenol with formaldehyde containing SO ₃ groups in the benzene ring);

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

Low water demand cement was prepared as follows.

Before the grinding procedure, the limestone rock was 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, a joint grinding of Portland cement and a water-reducing agent was carried out to a specific surface

550 m ² / g.

Next, carbonate-containing mineral material was added to the mill, and Portland cement and a water-lowering reagent were milled together with carbonate-containing mineral 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 dough prepared from Portland cement (composition 1 of Table 1) and cement dough 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 VI Modified high-quality concretes. Scientific publication. - M.: Publishing House of the Association of Building Universities, 2006, - 368 p.), and also change in masks limiting shear stress of 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 ΔP for cement paste was calculated by the formula:

ΔP = RCK / 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 cement paste cylinder 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 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 the composition of the prototype - cement low water demand from Portland cement, 50 wt.%, Mineral siliceous additives, 50 wt.%, In the form of silica sand and organic water-reducing reagent - plasticizer S-3. To obtain cement of low water demand, all the starting components were simultaneously loaded into a spring mill and they were ground together to a specific surface of 400-700 m ² / kg, which was monitored on a device for measuring the specific surface of the 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.

Example 3, as well as the following examples 4-6, 11, 12, relates to the preparation of low-water cement from Portland cement, 50 wt.%, Carbonate-containing limestone of the Serafimovskoye field, 50 wt.%, And organic water-lowering reagents - a condensation product of naphthalene sulfonic acid with formaldehyde - a superplasticizer S-3 TU 6-36-0204229-625, and Melflux 2651F hyperplasticizer, taken in an amount of 0.3-3.0% of the resulting cement mass of low water demand. First, Portland cement with a plasticizer was loaded into the mill, then they were grinded together to a specific surface of 550 (for examples 11, 12 - 400 and 700 m ² / kg, respectively), and then the mill was refilled with limestone and milled of these materials to obtain low water demand cement to a specific surface of 550 (for examples 11, 12 - 400 and 700 m ² / kg, respectively).

Examples 7-10 are similar to examples 3-6, 11, 12, with the difference that they took more Portland cement - 70 wt.% And a smaller amount of 30 wt.% Carbonate-containing mineral filler.

A comparison of the test results of the prototype and the proposed solution shows that as a result of using carbonate-containing material as a mineral filler instead of siliceous material, the normal density of the cement dough decreased even when using an organic water-lowering reagent in a minimum amount of 0.3% by weight of cement of low water demand, the water-reducing effect on 2.4-47.7%, cement paste density 1-10%, cement stone strength 0.9-51%, rheological improved characteristics: rheological ability ΔР increased from 120% to 150-490%, and the ultimate shear stress τ ₀ decreased from 29.7 to 19.1-1.9 Pa.

Claims (2)

1. A method of producing cement of low water demand, including grinding Portland cement, a mineral filler and an organic water-reducing reagent to a specific surface of 400-700 m ² / kg, characterized in that carbonate-containing material with a calcium carbonate fraction of at least 60 wt.% Is used as a mineral filler and the specified grinding is carried out by co-grinding Portland cement with an organic water-reducing reagent to the specified specific surface, and then grinding them with the addition of the specified carbonate-containing th material to the specified specific surface in the following ratio of components, wt.%:
Portland cement 50-70 The specified carbonate-containing material 30-50 Organic Water Reducing Reagent 0.3-3.0 in excess of 100% 2. Cement of low water demand, obtained by the method according to claim 1.