RU2351562C1 - Concrete mix for manufacture of thin-walled products - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention is related to construction materials, namely to compositions for concrete mixes reinforced with basalt fiber for manufacture of thin-walled products in the form of fencing and facing structures, such as facing tiles, ventilated facades, etc. Concrete mix for manufacture of thin-walled products contains Portland cement, basalt fiber with length of 12 mm, superplasticiser based on naphthalene sulfocompounds, water and mineral filler in the form of granite crushed stone sifting with fraction of 2-5 mm and sand with size module of 1-2.5, in ratio of 7:3 at the following ratio of components, wt %: Portland cement - 28.50-31.50, basalt fiber with length of 12 mm - 1.39-1.61, superplasticiser based on naphthalene sulfocompounds - 0.29-0.31, water -5.40-6.00, mineral filler - sifted granite crushed stone of fraction 2-5 mm and sand with size module of 1-2.5 - the rest.

EFFECT: higher strength for compression and tension in bending, frost resistance and water impermeability of thin-walled products.

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Description

The invention relates to building materials, namely, compositions of concrete mixtures reinforced with basalt fiber for the manufacture of thin-walled products in the form of enclosing and facing structures, such as facing tiles, for example, facade or basement, ventilated facades, etc.

It is known that reinforcing basalt fibers introduced into the concrete mix are able to inhibit the opening of cracks in concrete at the early plastic stage of its hardening, and are also able to inhibit the surface separation of water from the concrete mix, which improves the properties of hardened concrete.

Known concrete mixture, including Portland cement, silica sand, mineral fiber in the form of waste from basalt fiber and water, in the following ratio of components, wt.%: Portland cement - 20-22; quartz sand - 43-44, waste from basalt fiber production - 3.5-5 and water - the rest (30-32.5), and the ratio of water to cement (W / C) is 136 - 163% (see RF patent for invention No. 2288198, IPC8 С04В 28/02, С04В 14/38, С04В 111/27, application filing date 02.12.2005, published on 11.27.2006 “Concrete mix”).

The known composition is used for the manufacture of monolithic concrete structures by the gulf method, as well as for the manufacture of products in the form of thin-walled enclosing and facing structures.

However, products made from a known mixture, having a relatively high frost resistance (295-315 cycles) and sufficient water resistance (W4-W6), despite the presence of a reinforcing basalt fiber in the mixture, have low compressive strength (30-40 MPa), strength at bending (6.5-7 MPa) and abrasion (0.6 g / cm ² ), due to reducing the density, and hence the strength characteristics of the product with a very high water-cement ratio and non-optimal qualitative and quantitative ratio of components.

In addition, the use of a large amount of excess water in the mixture to ensure that the cement mortar fills the gaps between the particles of an inert mineral aggregate and gives the mixture the necessary fluidity leads to an uneven distribution of basalt fiber in the manufacturing process due to the separation of the mixture, accompanied by internal and surface release of water from the concrete mixture and gravitational settling of the fiber to the bottom of the mold, which also reduces its strength characteristics.

Known concrete mixture, including Portland cement M500, building sand, organic plasticizer - glycerin, basalt fiber from predetermined coarse fiber segments and water, in the following ratio of components, wt.%: Portland cement M500 - 14.1; building sand - 66.8-72.3; glycerin - 0.016; basalt fiber - 6.5-11; water - up to 100 (optimally 6.5), and the ratio of water to cement (H / C) is 46% (see copyright certificate for the invention No. 1778100, IPC 5 С04В 40/00, filing date September 10, 1990, published November 30, 1992, Bull. No. 44 "Method for the preparation of concrete mix").

The known mixture is intended for the manufacture of basalt-fiber-reinforced concrete products, such as partitions of industrial buildings or cladding panels, as well as for monoling nodes and joints.

A disadvantage of the known concrete mixture, despite the high (6.5-11 wt.%) Content of basalt fiber in the mixture, is the low strength characteristics of the products obtained (compressive strength is 28-32 MPa, axial tensile strength is 2.7-3 , 4 MPa), due to the decreasing density, and hence the strength characteristics of the product, increased water-cement ratio and non-optimal qualitative and quantitative ratio of components.

In addition, the use of an excess amount of water in the mixture to ensure that the cement mortar fills the gaps between the particles of an inert mineral aggregate and gives the mixture a fluidity leads to an uneven distribution of basalt fiber in the manufacturing process due to the separation of the mixture, accompanied by surface release of water from the concrete mixture and gravitational settling of the fiber on the bottom of the mold, which also reduces its strength characteristics.

A known fiber-reinforced concrete mixture used for the manufacture of enclosing and facing structures in the form of multilayer products of a given thickness with a thickness of each subsequent layer of 6 mm, including cement grade PC 500 DO-N 48, fine-grained sand, plasticizer S-3 as part of a chemical additive, fiberglass fiber from 21 to 40 mm long and water, with the following ratio of components, wt.%: cement - 45-53; fine-grained sand - 25-35; a chemical additive with a content of 9-10 wt.% plasticizer C-3 - 2-8; the specified fiber is 0.5-9; water 15-20, and the ratio of water to cement (W / C) is 26-33% (see RF patent for invention No. 2301207, IPC 8 С04В 28/00, С04В 14/44, С04В 111/27, filing date November 17, 2005, published on June 20, 2007, “Fiberglass Concrete (Variants)”).

The disadvantage of the known concrete mixture, despite the high (0.5-9 wt.%) Content in the mixture of fiberglass from 21 to 40 mm in length, are not high enough strength characteristics of the resulting multilayer products (compressive strength is 65-66 MPa, strength tensile bending is 23-24 MPa), due to reducing the density, and therefore the strength characteristics of the product, increased water-cement ratio and non-optimal qualitative and quantitative ratio of the components of the mixture.

In addition, the use of an excess amount of water in the mixture to ensure that the cement mortar fills the gaps between the particles of an inert mineral aggregate and gives the mixture a fluidity leads to an uneven distribution of the glass fiber during the manufacturing process due to the separation of the mixture, accompanied by surface release of water from the concrete mixture and gravitational settling of the glass fiber of each layer multilayer products, which also reduces its strength characteristics.

The closest to the claimed invention in terms of essential features is a concrete mixture for the manufacture of thin-walled products, including Portland cement, natural stone mineral aggregate in the form of granular, in particular granite, material with a particle size of between 0.1 and 6 mm, a superplasticizer based on naphthalenesulfonyl compounds and water for example, with the following ratio of components: Portland cement - 14.3% by volume, granite 0.2-0.6 mm - 8.6% by volume; 0.6-1.2 mm - 12.5% by volume; 1.2-2.5 mm - 22.3% by volume, 2.5-4.5 mm - 25.9% by volume and water with the addition of a plasticizer - 14.3% by volume, and the ratio of water to cement ( W / C) is 32% (see RF patent for invention No. 251118, IPC 7 С04В 28/02, В28В 23/00, В28В 7/08, В28С 5/00, filing date January 27, 1997, published on June 20, 1997 .2000, “Method and device for the production of cemented tile products and obtained tile products”).

Known concrete mixture is used for the manufacture of thin single-layer tiles or products with a thickness of 15-20 mm, preferably 17 mm.

Products from the known concrete mixture have a balanced composition of granular stone material and a cementing matrix filling the voids and gaps between the above material, and the ratio of water to cement (W / C) is 25-36% (preferably 28-32%).

Products obtained from a known composition that do not contain a reinforcing material have rather high physical and mechanical properties: specific gravity 2.45 kg / dm ³ , hygroscopicity 2.5-3.1% by weight, bending strength 13.5-14 6 MPa, abrasion resistance 290-320 mm ³ .

However, the known composition does not allow to obtain thinner products with a complex of increased characteristics, including tensile strength during bending, water resistance and frost resistance, which is due to the increased water-cement ratio, which reduces the density and, therefore, strength characteristics of the product.

The claimed invention provides for the production of concrete mix for the manufacture of thin-walled products with a thickness of up to 10 mm with improved technical characteristics that exceed the achieved level of technology.

The technical result of the claimed invention is to increase the compressive strength, tensile strength during bending, frost resistance and water resistance of thin-walled products by ensuring uniform distribution of the mixture components over the entire thickness of the product while maintaining a dense spatial structure.

The specified technical result is achieved by the fact that in the known concrete mixture for the manufacture of thin-walled products, including Portland cement, mineral aggregate, superplasticizer based on naphthalene sulfo compounds and water, the mineral aggregate contains screening of granite crushed stone fraction 2-5 mm and sand with a particle size module of 1-2.5 taken in a ratio of 7: 3, and the concrete mixture additionally contains basalt fiber 12 mm long, with the following ratio of components, wt.%:

Portland cement 28.50-31.50 12 mm basalt fiber 1.39-1.61 superplasticizer based naphthalenesulfonyl compounds 0.29-0.31 water 5.40-6.00 mineral aggregate - screening granite crushed stone fraction 2-5 mm and sand with particle size 1-2.5 rest

Qualitative and quantitative composition of an inert mineral aggregate, namely screening of crushed granite fractions from 2 to 5 mm and sand with a particle size module of 1-2.5, taken in a ratio of 7: 3, in combination with basalt fiber introduced into the mixture with a fiber length of 12 mm in the amount of 1.39-1.61 wt.%, which reinforces the inventive concrete mixture containing water in the minimum possible amount for this composition, allows for a dense compact and uniform distribution of all components of the mixture over the entire thickness of the product with the complete exception of layered I components of the mixture during its manufacture due to the total absorption of water components of the mixture, precluding their gravitational settling.

In addition, the presence in the inventive concrete mixture of basalt fiber with a fiber length of 12 mm within the claimed limits determines the maximum possible reduction in water demand of the mixture with the optimum quantitative and qualitative composition of an inert mineral aggregate, Portland cement and superplasticizer, since fiber, increasing the strength characteristics of the mixture and product, It is also a kind of conductor of water, making it possible to evenly distribute it in the mixture, without causing separation of the components.

The composition of the concrete mixture uses the lowest possible amount of water, namely 5.4-6.0 wt.% With a ratio of water to cement by weight (W / C) in the range of 17-21%, of which 15% goes to hydration, and the rest gives the mixture the necessary fluidity.

The introduction of Portland cement in the amount of 28.5-31.5% in the concrete mixture is optimal, since the best strength indicators are provided in this range, an increase in its content increases the possibility of cracks, and a decrease in its content reduces the strength and frost resistance of thin-walled products made from concrete .

Introduction to the concrete mix of basalt fiber with a fiber length of 12 mm with high strength properties is optimal for the production of thin-walled products up to 10 mm thick, and the amount of 1.39-1.61 wt.% Provides the best strength properties, an increase in its content is not practical from an economic point of view vision, and a decrease in its content affects the uniform distribution of water.

The introduction into the concrete mixture of a superplasticizer based on naphthalenesulfonyl compounds in an amount of 0.29-0.31 wt.% Is optimal, making the mixture more plastic, but not preventing the subsequent removal of air from the mixture during hydration.

When a solution of water with superplasticizer is added to the prepared concrete mixture in the minimum required amount, the mixture does not spread, but begins to roll into balls with needles of basalt fiber with a diameter of 2-3 cm, which in the course of rotation of the concrete mixer for a short period of time (2-3 minutes) acquire a high density and hardness.

A ready-made dense mixture with reinforcing needles of basalt fiber, containing a minimum number of pores, during vibroforming of products with a thickness of up to 10 mm (for example, thin tiles) is even more compacted over its entire thickness with the removal of air and minimizing the network of microcapillaries between the grains of the mineral aggregate, due to this a very small amount of water, basalt fiber remains evenly distributed over the entire thickness of the product, not settling to the bottom of the mold, which increases the compressive strength, tensile strength at and bending of finished thin-walled products, as well as their frost resistance and water resistance.

Technical solutions that coincide with the totality of the essential features of the claimed invention have not been identified, which allows us to conclude that it meets such a patentability condition as “novelty”.

The claimed essential features of the invention, predetermining the receipt of the specified technical result, do not explicitly follow from the prior art, which allows us to conclude that the claimed invention meets such a patentability condition as "inventive step".

The patentability condition "industrial applicability" is confirmed by specific examples of concrete mix for the manufacture of thin-walled products, set forth in the section "Information confirming the possibility of carrying out the invention."

For the manufacture of thin-walled products from the inventive concrete mixture is used:

- Portland cement without mineral additives of a grade no lower than ПЦ 400 ДО, in particular ПЦ 500 ДО, satisfying GOST 10178-85;

- mineral aggregate -

screening of crushed stone from igneous rocks, in particular granite, satisfying the requirements of GOST 8267-93, with a fraction size of 2-5 mm, according to GOST 26633-91, the screening grade for compressive strength not lower than 100 MPa, for frost resistance is not used as a large aggregate below F300;

building sand with a fineness modulus M _to 1-2.5 according to GOST 26633-91 is used as a smaller aggregate, while in sand with a fineness modulus of more than 2 (medium-sized sand) the particle content of less than 0.16 mm does not exceed 10% , with a particle size modulus of 2 to 1.5 (fine sand) - 15% and less than 1.5 (very fine sand) - 25% by weight;

- a superplasticizer based on naphthalenesulfonyl compounds, in particular the POLYPLAST SP-1 superplasticizer (dry powder), which is a mixture of sodium salts of polymethylene naphthalenesulfonic acids of various molecular weights, according to TU 5780-002-58042865-05;

- water with a temperature not lower than 16 ° C, satisfying the requirements of GOST 23732;

- basalt fiber (basalt coarse fiber BGV 150) with a fiber diameter of 150 μm and a fiber length of 12 mm according to TU 5769-001-46973937-03, according to which the tensile strength of a fiber with a diameter of 150 mm is at least 180 MPa with a length of 1 kg of thread 35714 m, and alkali resistance of at least 90%.

The preparation of concrete mixture for the manufacture of thin-walled products was carried out in the following order.

Preliminarily calculated the quantitative content of each component of the concrete mixture and weighed.

Suspended sand and gravel screenings were loaded into a gravity concrete mixer. Then basalt fiber was added and the mixture was thoroughly mixed for 40-60 seconds at a speed of 20-24 rpm for uniform distribution of fiber between the dry components - sand and screenings.

After that, Portland cement was added to the gravity concrete mixer and the mixture was mixed again.

In the calculated mass of water, the calculated mass of the POLYPLAST SP-1 superplasticizer was dissolved, then a water solution with a plasticizing additive was introduced into the mixture at the far end of the concrete mixer pear in small portions with constant stirring.

The mixture moistened with the solution began to roll into balls with a diameter of 2-3 cm. The balls obtained during the rotation of the concrete mixer pear in a short period of time (2-3 minutes) acquired high density and hardness.

The finished mixture was loaded into molds for the manufacture of products, such as tiles, and a vibroforming process was carried out, the purpose of which was to compact the material throughout its thickness, removing air from it and minimizing the network of microcapillaries between the grains of the mineral aggregate.

After that, the products are packaged in thermal cassettes, in which the set temperature and humidity are observed, where for a certain time the process of cement hydration and the process of curing take place.

Products made from the inventive concrete mixture, depending on the overall dimensions, have a thickness of 6 to 10 mm.

Examples of concrete mixes for the manufacture of thin-walled products, the quantitative ratio of the components of which were within the protected limits, are shown in Table 1.

The composition of the concrete mixture for the manufacture of thin-walled products

Table 1 Components The composition of the components of the concrete mixture, wt.% one 2 3 four 5 6 7 8 9 Portland cement PC 500 DO 28.50 28.50 28.50 30.00 30.00 30.00 31,50 31,50 31,50 Basalt fiber (d 150 μm), length 12 mm 1.41 1.51 1,61 1.40 1,50 1,60 1.39 1.49 1,59 Superplasticizer SP-1 0.29 0.29 0.29 0.30 0.30 0.30 0.31 0.31 0.31 Water 5.40 5.40 5.40 5.70 5.70 5.70 6.00 6.00 6.00 Screening of granite crushed stone fr. 2-5 mm 45.10 45.00 44.90 43.80 43.80 43.70 42.60 42.50 42.40 Sand M _to 1-2.5 19.30 19.30 19.30 18.80 18.70 18.70 18,20 18,20 18,20

The test results of thin-walled products (tiles) made from the given concrete mixes are shown in Table 2.

Physico-mechanical properties of thin-walled products made from the inventive concrete mixture

table 2 Indicator Concrete mixes one 2 3 four 5 6 7 8 9 Compressive strength, MPa 92.0 94.0 97.0 93.0 95.0 98.0 94.0 97.0 100.0 Tensile strength in bending, MPa 32,0 34.0 35.0 34.0 36.0 38,0 39.0 41.0 41.0 Frost resistance, cycles > 300 > 300 > 300 > 300 > 300 > 300 > 300 > 300 > 300 Water Resistant, W twenty twenty twenty twenty twenty twenty twenty twenty twenty Abrasion, g / cm ² 0.14 0.13 0.12 0.14 0.13 0.12 0.14 0.13 0.12

As can be seen from Table 2 tests, products from the compositions of the proposed concrete mixture have a complex of increased indicators, namely compressive strength, tensile strength in bending, abrasion, and water resistance (at least W20) and frost resistance (at least 300 cycles, up to 700 -900 cycles) with a density of products of 2.5 g / cm ³ compared with known analogues, which allows to reduce the thickness of products made from the inventive concrete mixture, to a value of from 6 to 10 mm

Claims (1)

A concrete mixture for the manufacture of thin-walled products, including Portland cement, a mineral aggregate, a superplasticizer based on naphthalenesulfonic compounds and water, characterized in that the mineral aggregate contains a screening of granite crushed stone fraction 2-5 mm and sand with a particle size module of 1-2.5 in a ratio of 7: 3 moreover, the concrete mixture additionally contains basalt fiber 12 mm long in the following ratio of components, wt.%:
Portland cement 28.50-31.50 12 mm basalt fiber 1.39-1.61 superplasticizer based naphthalenesulfonyl compounds 0.29-0.31 water 5.40-6.00 mineral aggregate - screening granite crushed stone fraction 2-5 mm and sand with particle size 1-2.5 rest