RU2778123C1 - Fine-grained self-compacting concrete mix - Google Patents

Abstract

FIELD: building materials.

SUBSTANCE: invention relates to building materials, in particular to fine-grained self-compacting concrete mixtures, and can be used for monolithic concreting and repair work, where the technology requires increased mixture mobility, high early and design strength of fine-grained concrete. The fine-grained self-compacting concrete mixture contains, wt.%: Portland cement without additives of the CEM I 42.5B class with a normal density of 25-26% 27.0-27.1, fine natural sand with a fineness modulus of 1.8 58.6-61.0, active mineral additive - a powder obtained from polymineral clay after heat treatment at a temperature of 700 ° C for 2 hours and subsequent grinding to a specific surface of 7800 cm²/g 3.0-4.8, powder hyperplasticizer based on polycarboxylate ether brand "Melflux 5581 F "0.3, water - the rest.

EFFECT: increasing the compressive strength of fine-grained concrete.

1 cl, 2 tbl

Description

The invention relates to building materials, in particular to fine-grained self-compacting concrete mixtures, and can be used for monolithic concreting and repair work, where the technology requires increased mixture mobility, high early and design strength of fine-grained concrete.

Known composition of sandy concrete, including Portland cement, quartz sand with a fineness modulus of 2.7-3.2, chemical water treatment sludge (SHHVO) with a specific surface area of 1200-1300 m ² /kg, microsilica, superplasticizer "Melflux 2651 F" and water, with the following ratio of components, wt.%: Portland cement - 16.7-18; quartz sand - 68.4-70.0; WHVO - 1.2-2.5; microsilica - 0.8-2.8; superplasticizer - 0.08-0.09; water - 8.9-10.1 [1].

The disadvantage of this concrete mixture is the insufficiently high compressive strength of sand concrete at the age of 28 days, as well as the need to use large quartz sands with a fineness modulus of 2.7-3.2, which are in short supply in many regions of the Russian Federation.

A fine-grained concrete mixture is known, including Portland cement, medium-sized natural sand, silica fume and metakaolin as mineral additives, a polyfunctional superplasticizer based on polyoxyethylene derivatives of polymethacrylic acid "Dynamics PK" and water, in the following ratio, wt.%: Portland cement - 19- 19.9; sand - 67-67.5; microsilica - 0.8-1.81; metakaolin - 0.5-1.08; superplasticizer - 0.1-0.2; water - the rest [2].

The disadvantage of this concrete mix is the low strength characteristics of the resulting concrete and the need to use sands of medium size (MK=2.0-2.5).

Known fine-grained concrete mix, including Portland cement, quartz sand, filler, powdered hyperplasticizer based on Melflux polycarboxylate ether, water-retaining additive, water, as Portland cement contains Portland cement without additives with an indicator of normal density of the cement paste of not more than 26%, as a filler, microcalcite with the content of calcium carbonate is not less than 97% with particles of a fraction of not more than 120 microns - not less than 98%, including fractions of less than 20 microns - not more than 7%, as a water-retaining additive, condensed uncompacted silica fume with a content of amorphous silica of not less than 85% and specific surface 12-25 m ² /g or metakaolin with amorphous alumina content of at least 40%, amorphous silica - at least 50%, amorphization of the aluminosilicate structure of at least 90% and a specific surface of 1.2-2.5 m ² /g with the following the ratio of components, wt.%: Portland cement without additives with an indicator of normal density of the cement paste is not more than 26% 15.8-23.6; quartz sand 35.6-61.4; microcalcite with a calcium carbonate content of at least 97% with particles of a fraction of not more than 120 microns - not less than 98%, including fractions of less than 20 microns - not more than 7% 1.8-27.4; powder hyperplasticizer based on Melflux polycarboxylate ether 0.14-0.30; non-compacted condensed microsilica with an amorphous silica content of at least 85% and a specific surface of 12-25 m ² /g or metakaolin with an amorphous alumina content of at least 40%, amorphous silica of at least 50%, amorphization of the aluminosilicate structure of at least 90% and a specific surface 1.2-2.5 m ² /g 0.81-4.20; water the rest [3].

The known technical solution makes it possible to obtain self-compacting concrete mixtures with standard cone settlement values of 26-28 cm (P5), to increase the compressive strength at the design age of fine-grained concrete to the level of high-strength concrete with grade strength M500-M1000 and higher (class B40-B80 and higher). ), use in their composition portland cements of reduced grades (with an activity of 33-41 MPa), as well as very fine quartz sands with a fineness modulus of 1.4 (known compositions No. 7, 8 and 10). However, these compositions contain quite expensive components - filler microcalcite KM 100, water-retaining additives (condensed uncompacted microsilica MK-85, metakaolin VMK-40), which contributes to an increase in the cost of self-compacting mixtures and products based on them.

The closest technical solution to the claimed invention is a fine-grained self-compacting mixture, including Portland cement, quartz sand with particle size modulus M _cr =1.9, quartz filler with a specific surface area of 100 m ² /kg, polycarboxylate superplasticizer "Glenium ACE 430", hardening accelerator "X -SEED 100" and water, at the following ratio of components, wt.%: Portland cement - 44.2-44.7; quartz sand - 33.1-39.1; quartz filler - 5.6-11.1; superplasticizer - 0.3-0.4; hardening accelerator - 0.2; water - 10-11.1 [4].

This solution makes it possible to obtain self-compacting concrete mixtures using fine quartz sands with a size modulus of 1.9. The disadvantages of the prototype are the increased consumption of Portland cement (44.2-44.7 wt.%), the need to use expensive quartz filler with a specific surface area of 100 m ² /kg with insufficiently high early strength at the age of 1 day (20-22.2 MPa ).

The technical result, when using the claimed invention, is to increase the compressive strength of fine-grained concretes obtained on the basis of self-compacting mixtures in the early (1st day - at least 25 MPa) and design age (28 days - at least 65 MPa (not below class B50) due to the use of optimal complexes of additives based on powdered polycarboxylate hyperplasticizer of the Melflux 5581 F brand and an active mineral additive obtained on the basis of thermally activated (2 hours at a temperature of 700 ° C) polymineral clay of the Nikitsky deposit of the Republic of Mordovia, crushed to a specific surface 7800 cm ² /g.

The essence of the invention lies in the fact that the fine-grained self-compacting concrete mixture contains Portland cement without additives of the CEM I 42.5B class with a normal density of 25-26%, fine natural sand with a fineness modulus of 1.8, a powder obtained from polymineral clay after heat treatment at a temperature of 700 °C for 2 hours and subsequent grinding to a specific surface area of 7800 cm ² /g, powder hyperplasticizer based on polycarboxylate ether brand "Melflux 5581 F" and water, in the following ratio of components, wt.%:

Portland cement class CEM I 42.5B with normal density 25-26% 27.0-27.1 fine natural sand with fineness modulus 1.8 58.6-61.0 powder obtained from polymineral clay after heat treatment at 700°C for 2 hours and subsequent grinding to a specific surface 7800 cm ² /g 3.0-4.8 powder based hyperplasticizer polycarboxylate ether Melflux 5581 F 0.3 water rest

For the manufacture of fine-grained self-compacting concrete mixtures, the following were used:

- Portland cement of the CEM I 42.5B class with a normal density of 25-26%, produced by OJSC Mordovcement, GOST 31108-2020 “General construction cements. Specifications";

- natural fine quartz sand of the Bolotnikovsky quarry of the Republic of Mordovia with particles no larger than 5 mm, fineness modulus 1.8, GOST 8736-2014 “Sand for construction work. Specifications";

- active mineral additive based on thermally activated polymineral clay from the Nikitsky deposit of the Republic of Mordovia;

- powdered hyperplasticizer based on polycarboxylate ether brand "Melflux 5581 F" manufactured by BASF Construction Solutions (Trostberg, Germany);

- water for concretes and mortars according to GOST 23732-2011.

The method for preparing an active mineral additive based on polymineral clay raw materials consists in preliminary grinding of the initial raw material (polymineral clay of the Nikitsky deposit of the Republic of Mordovia with a content of 62% of reaction minerals (kaolinite and illite) to a fraction of not more than 2.5 mm, heat treatment at a temperature of 700 ° C for 2 hours and subsequent grinding to a specific surface of 7800 cm ² /g Optimization of the technological mode of obtaining an active mineral additive was carried out on the basis of the results of studies conducted for the following combinations of factors: firing temperature - 400-800°C; firing duration - 2-4 hours, the concentration of the additive is 2-18% by weight of the binder.

The mixing of the components of the concrete mixture is carried out sequentially, and initially Portland cement and powder hyperplasticizer are mixed in the mixer for 1-2 minutes, then the mineral additive based on polymineral clay raw materials is poured and mixed for 1-2 minutes, after which quartz sand is introduced and the dry mixture is mixed until smooth for 1-2 minutes. At the final stage, the required amount of water is added and mixed until a concrete mixture of the required mobility and uniformity is obtained. The total time for preparing the concrete mixture is from 8 to 10 minutes (this time includes additional operations for backfilling the components).

To determine the mobility of the concrete mixture, as for the prototype, the flow from the Hegermann cone was determined according to GOST 310.4-81 “Cements. Methods for determining the strength in bending and compression. In addition, the draft of concrete mixes from a standard cone was determined according to GOST 10181-2014 “Concrete mixes. Test Methods". According to [5], when developing compositions for self-compacting fine-grained and fine-grained concrete mixes of workability classes SF1-SF3, the draft of a standard cone should be from 25.5 to 28 cm.

After the preparation of the concrete mixture, beam samples 40*40*160 mm in size and cube samples with a rib length of 100 mm were made in accordance with GOST 10180 “Concrete. Methods for determining the strength of control samples. All samples up to the design age of 28 days were stored under normal conditions (temperature 20 ± 2°C, relative humidity of the ambient air of at least 90%, created in the normal hardening chamber). Tests of specimens-beams with the determination of tensile strength in bending and in compression were carried out at the age of 1 and 28 days, specimens-cubes in compression - at the design age. The density of the samples in the equilibrium-moisture state was also determined.

The compositions of the proposed fine-grained self-compacting concrete mixtures and the prototype are presented in table. 1. The results of testing these compositions and concretes based on them are given in table. 2.

The mobility of concrete mixtures according to the proposed recipe when flowing from the Hegermann cone is 230-280 mm, which is comparable to or higher than the prototype (220-240 mm), the draft of the standard cone is 26-28 cm (mobility mark according to GOST 7473-2010 - P5). According to [5], the proposed compositions can be attributed to self-compacting mixtures with a cone draft of at least 26 cm and a flow diameter of at least 55 cm.

From a fine-grained self-compacting concrete mixture, concretes were obtained with a compressive strength of 25.6-31.5 MPa on the 1st day of hardening and at a design age of 66.7-72.1 MPa (on sample cubes 100 * 100 * 100 mm) , which corresponds to classes B50-B55. The density of concrete in the equilibrium-moisture state at the age of 28 days is 2282-2298 kg/m ³ .

Thus, in comparison with the known technical solution, the present invention makes it possible to obtain fine-grained self-compacting concrete mixtures with increased compressive strength in early (1 day - at least 25 MPa) and design age (28 days - at least 65 MPa (not lower than the class B50)) without the use of hardening accelerators and expensive quartz filler with a specific surface of 100 m ² /g, expand the range of fine-grained self-compacting concretes with the possibility of using an active mineral additive in their composition (instead of more expensive additives - silica fume and metakaolin) based on thermally activated clay and fine natural quartz sands with a fineness modulus of 1.8, widely distributed in many regions of the Russian Federation.

Sources of information

1. RU 2569947, IPC C04B 28/04, C04B 18/04, C04B 24/24, C04B 103/46, publ. 12/10/2015.

2. RU 2627344, IPC C04B 28/04, C04B 18/04, C04B 18/14, C04B 24/24, C04B 111/20, C04B 103/32, publ. 08/07/2017.

3. RU 2657303, IPC C04B 28/04, C04B 14/06, C04B 14/26, C04B 24/26, C04B 103/32, C04B 103/46, C04B 111/20, publ. 06/13/2018.

4. RU 2603991, IPC C04B 28/04, C04B 24/24, C04B 103/32, C04B 103/14, C04B 111/62, publ. 12/10/2016.

5. Kalashnikov V.I. Calculation of compositions of high-strength self-compacting concretes / V.I. Kalashnikov // Building materials. 2008. No. 10. pp. 4-6.

Table 1 - Compositions of fine-grained self-compacting concrete mixtures

No.
composition Portland cement (specific surface area 360 m ² /kg) Portland cement
(class CEM I 42.5B) Quartz sand
with fineness modulus 1.9 Quartz sand
with fineness modulus 1.8 quartz filler,
S _beats \u003d 100 m ² / kg Active mineral additive based on thermally activated polymineral clay Polycarboxylate Superplasticizer
Glenium ACE 430 Hyperplasticizer
Melflux 5581F hardening accelerator
X-SEED 100 Water 1 Prototype 44.2 - 33.1 - 11.1 - 0.3 - 0.2 11.1 2 Prototype 44.7 - 39.1 - 5.6 - 0.4 - 0.2 10.0 3 - 27.0 - 61.0 - 3.0 - 0.3 - 8.7 four - 27.1 - 58.6 - 4.8 - 0.3 - 9.2

Table 2 - Properties of fine-grained self-compacting concrete mixes,

fine-grained concretes based on them

No.
composition Mobility of the mixture Beam samples 40*40*160 mm in size Sample Cubes
100*100*100mm Spread from the Hegermann cone, mm Draft of a standard cone (grade of the mixture by mobility), cm bending strength,
MPa, aged, days Compressive strength,
MPa, aged, days Density at design age, kg / m ³ Strength
during compression at the design age,
MPa (class of concrete) one 28 one 28 1 Prototype 220-240 -* -* -* 20.0 -* -* -* 2 Prototype 220-240 -* -* -* 22.2 -* -* -* 3 230 26 (P5) 5.60 8.69 25.6 66.3 2298 66.7 (B50) four 280 28 (P5) 5.96 8.23 31.5 71.2 2282 72.1 (B55)

Note:

* The specified indicator of the concrete mix and concrete for the prototype was not determined.

Claims (2)

Fine-grained self-compacting concrete mixture, consisting of Portland cement, quartz sand, active mineral additive, plasticizing additive, water, characterized in that Portland cement without additive class CEM I 42.5B with a normal density of 25-26% is used as Portland cement, with a normal density of 25-26%, as quartz sand - fine natural sand with a fineness modulus of 1.8, as an active mineral additive - a powder obtained from polymineral clay after heat treatment at a temperature of 700 ° C for 2 hours and subsequent grinding to a specific surface of 7800 cm ² /g, as a plasticizing additive - powder hyperplasticizer based on polycarboxylate ether brand "Melflux 5581 F", with the following ratio of components, wt.%: Portland cement class CEM I 42.5B with normal density 25-26% 27.0-27.1 fine natural sand with fineness modulus 1.8 58.6-61.0 powder obtained from polymineral clay after heat treatment at 700°С for 2 hours and subsequent grinding to a specific surface 7800 cm ² /g 3.0-4.8 powder based hyperplasticizer polycarboxylate ether Melflux 5581 F 0.3 water rest