RU2762272C1 - Raw material mixture for protective coating - Google Patents

Abstract

FIELD: building materials.

SUBSTANCE: invention relates to the field of building materials and can be used to protect the surfaces of concrete and reinforced concrete structures in civil and industrial construction. The raw mixture contains sand with a fraction of 0.315 mm, magnesia limestone with a specific surface area S_sp = 280 m²/kg, metakaolin based on kaolinite clays with a specific surface area S_sp = 1300 m²/kg, and a complex additive consisting of microsilica with a specific surface area S_sp = 2000 m²/kg, dry polycarboxylate polymer based on methacrylic acid with bulk density D = 0.520 g/cm³, pH value pH = 6.0 and potassium formiate with the following ratio of components, wt.%: the specified microsilica 87.0-87.5; the specified polycarboxylate polymer 4.1-4.3; potassium formate 8.4-8.7, with the following ratio of the components of the raw mixture, wt. %: Portland cement 44.5-46.3; the specified sand 26.9-27.4; the specified limestone 6.4-6.8; the specified metakaolin 1.6-1.80; the specified complex additive 4.8-5.1; water 14.0-14.4.

EFFECT: increase in the adhesion strength to the surface of the concrete base and increasing the corrosion resistance of the protective coating against magnesia corrosion.

1 cl, 1 tbl

Description

The invention relates to the field of building materials and can be used to protect the surfaces of concrete and reinforced concrete structures in civil and industrial construction.

Known raw mixture used for the protective coating of a concrete surface contains wt. %: cement - 36.0-40.0; sand - 39.0-49.0; sodium nitrate - 0.9-1.8; sodium carbonate - 2.0-3.0; sodium sulfate - 2.5-3.6; calcium chloride - 0.05-0.15; calcium carbide - 0.75-1.15; calcium hydroxide - 0.8-1.0; water - the rest (RU No. 2072335, С04В 22/08, Е04В 1/64, В28 19/00, С04В 28/00, 27.10.1997).

The disadvantage of this raw mixture is insufficient adhesion strength to the surface of the concrete base and insufficient corrosion resistance against magnesia corrosion.

Known raw mixture used for the protective coating of a concrete surface, including Portland cement, sand, montmorillonite clay with a specific surface area of at least 150 m ² / kg, a complex additive consisting of silica fume with S _beats = 2000 m ² / kg, additives CMID-4 and 20% solution of orthosilicic acid sol with pH = 3-4 and water with the following ratio of components, wt. %: Portland cement - 23.00-28.81; sand - 59.00-64.00; montmorillonite clay with S _yd ≥150 m ² / kg - 0.69-0.83; microsilica with S _yd = 2000 m ² / kg - 1.16-1.30; additive CMID-4 - 0.19-0.22; 20% solution of orthosilicic acid sol with pH = 3-4 - 0.14-0.17; water - 10.01-10.48. (RU No. 2305671, С04В 41/65, 10.09.2007).

The disadvantage of this raw mixture is insufficient adhesion strength to the surface of the concrete base and insufficient corrosion resistance against magnesia corrosion.

The closest in technical essence to the claimed raw mixture for a protective coating is a raw mixture consisting of the following components, wt. %: Portland cement - 30.3-32.3; aggregate, represented by sand with a maximum fraction size of 0.63 mm, in the amount of 40.4-40.9; finely ground dolomitized limestone with a specific surface area of particles of 200 m ² / kg in an amount of 8.1-8.6; complex additive - 3.2-3.7 and water - 16.0-16.5, complex additive consists of the following components, wt. %: microsilica with a specific surface area of particles of 2000 m ² / kg - 47-49; alumina cement - 24.5-25.0; gypsum CaSO ₄ ⋅nH ₂ O - 9.8-10.2; plasticizer C-3 - 3.7-4.0; sol of silicic acid H ₄ SiO ₄ with a density of 1.014 g / cm ³ and pH = 3.5-3.0-3.4; bentonite clay with a specific surface area of 500 m ² / kg - 10.0-10.4 (RU No. 2396235, С04В 41/63, С04В 41/68, 08/10/2010).

The disadvantage of this technical solution is insufficient adhesive strength to the surface of the concrete base and insufficient corrosion resistance against magnesia corrosion.

The problem to be solved by the invention is to create a raw mixture for a protective coating that has increased adhesive strength to the surface of a concrete base and has increased corrosion resistance relative to magnesia corrosion.

The task is achieved by the fact that the raw mixture for the protective coating contains Portland cement, sand, limestone, a complex additive and water, contains sand with a fraction of 0.315 mm as sand, and finely ground magnesia limestone with a specific surface area is used as limestone. S _yd = 280 m ² / kg, additionally contains metakaolin based on kaolinite clays with a specific surface of 1300 m ² / kg, a mixture consisting of micro-silica with a specific surface of S _yd = 2000 m ² / kg is used as a complex additive, dry polycarboxylate copolymer based on methacrylic acid with a bulk density D = 0.520 g / cm ³ and a pH value pH = 6.0 and potassium formate with the following ratio of components, wt. %:

- specified microsilica 87.0-87.5 - specified polycarboxylate polymer 4.1-4.3 - potassium formate 8.4-8.7,

with the following ratio of the components of the raw mixture, wt. %:

- Portland cement 44.5-46.3 - specified sand 26.9-27.4 - specified limestone 6.4-6.8 - specified metakaolin 1.6-1.8 - specified complex additive 4.8-5.1 - water 14.0-14.4

The use of a complex chemical additive based on a polycarboxylate copolymer of methacrylic acid has a plasticizing effect, which helps to reduce the water consumption required to prepare the mortar mixture, the required mobility, and contributes to the compaction of the structure of the protective coating. The presence of potassium formate in the additive increases the degree of hydration of Portland cement, having a positive effect on increasing the adhesion strength of the coating to the concrete base as a result of the penetration of highly mobile potassium cations from the additive into the concrete base, contributing to the possible occurrence of hydration processes with unreacted cement in the pores of the concrete base. The hydrated phases formed in the protective coating and in the concrete base during hardening enter into chemical interaction. The result of this interaction is the formation of a strong chemical bond according to the donor-acceptor mechanism, which leads to the formation of a strong contact zone according to schemes (1) and (2)

and, as a consequence, to increase the adhesion of the coating to the concrete base, that is, to increase the adhesion strength of the coating to the concrete base.

As a result of an increase in the degree of hydration of Portland cement, both in the coating and in the base, the amount of Ca (OH) ₂ increases, which is formed as a result of the following hydration reaction 3CaO⋅SiO ₂ + (n + 1) H ₂ O = 2CaO⋅SiO ₂ ⋅nH ₂ O + Ca (OH) ₂ . In parallel, the reactivity of microsilica increases in the presence of polycarboxylate; and the resulting hydrolytic lime Ca (OH) ₂ enters into synthesis reactions with microsilica, which is part of the additive, forming sparingly soluble calcium hydrosilicates, which compact the concrete structure and additionally have increased resistance to magnesia corrosion.

The presence in the composition of the raw mixture of metakaolin, which has an increased specific surface area and a layered structure, contributes to an increase in the density of the forming structure of the protective coating, preventing the penetration of excess moisture and soluble aggressive salts from the environment into the depth of the coating, thus further increasing the corrosion resistance of the protective coating. The presence of finely ground magnesian limestone in the composition of the raw material mixture increases the workability of the mortar mixture, during the hydration of which basic calcium carbonates CaCO3⋅Ca (OH) ₂ and magnesium hydrosilicates 2 MgO⋅SiO ₂ ⋅nH ₂ O are formed, characterized by increased strength, the formation of which contributes to the formation of strong and flexible contacts between the coating and the base, increasing the adhesion strength of the repair-protective coating to the concrete base.

As of the filing date of the application, in the opinion of the authors and the applicant, the declared raw mixture for the protective coating is not known and this technical solution has a worldwide novelty.

The claimed set of essential features exhibits a new property with the combined use of a complex chemical additive of metakaolin and finely ground magnesian limestone, providing a super-cumulative effect, consisting in achieving increased hydration activity of the coating components and unreacted cement of the concrete base, ensuring the formation of strong contacts between the coating and the base, while ensuring the formation of a strong and dense structure of the protective coating, which prevents the penetration of excess moisture and aqueous solutions of aggressive salts into the coating. All of the above has a positive effect on the creation of a protective coating with increased adhesion strength to the base and increased corrosion resistance relative to magnesia corrosion.

A mixture including Portland cement, sand with a fraction of 0.315 mm, finely ground magnesian limestone with a specific surface area of S _yd = 280 m ² / kg, metakaolin based on kaolinite clays with a specific surface area, S _beats = 1300 m ² / kg, a complex additive consisting of micro -kremnezema with S _ud = 2000 m ² / kg dry polycarboxylate copolymer based on methacrylic acid with a bulk density D = 0,520 g / cm and a pH value of pH = 6.0 and potassium formate, produces a protective coating, characterized by increased adhesion strength to a concrete base and increased corrosion resistance relative to magnesia corrosion.

In the opinion of the applicant and the authors, the claimed invention meets the criterion of protectability - an inventive step.

The claimed invention is industrially applicable and can be used to protect surfaces of concrete and reinforced concrete structures in civil and industrial construction.

An example of a specific implementation.

Prepare the raw mixture as follows:

1. Preparation of a complex supplement.

1.1. Dose microsilica with a specific surface area, S _yd = 2000 m ² / kg;

1.2. Dose dry polycarboxylate copolymer based on methacrylic acid with bulk density D = 0.520 g / cm and pH = 6.0;

1.3. Dose potassium formate;

1.4. Components dosed according to clause 1.1. - 1.3. are transported to a paddle mixer, where they are thoroughly mixed until a homogeneous mixture is obtained, the finished mixture is transported to a storage hopper.

2. Preparation of dry mix for protective coating:

2.1. Dose Portland cement;

2.2. Sand with a fraction size of 0.315 mm is dispensed;

2.3. Dose metakaolin based on kaolinite clays of the Chelyabinsk region with a specific surface area of 1300 m ² / kg;

2.4. Dose magnesian limestone with a specific surface area, S _beats = 280 m ² / kg;

2.5. Dose out the complex additive prepared according to item 1.4;

2.6. All components dosed according to clause 2.1. - 2.5., Transported to a paddle mixer, where all components are thoroughly mixed until a homogeneous fine powder is obtained, which is a dry mixture for a protective coating. 3. Preparation of a mortar mixture based on a dry mixture for a protective coating:

3.1. The dry building mixture prepared according to clause 2.6 is dispensed;

3.2. Dose water;

3.3. The components dosed according to clause 3.1 are mixed with an electric drill. and p. 3.2. until a homogeneous, lump-free, movable mass is obtained, which is used for its intended purpose as a protective coating and from which cube samples are made with a size of 7.07 × 7.07 × 7.07 cm, the hardening of which was carried out under normal conditions and upon reaching the design age 28 days, the samples were placed in a bath with a 5% solution of magnesium chloride, MgCl ₂ , where they were stored for 360 days and in parallel the samples were stored under normal conditions. Based on the test results, the corrosion resistance coefficient was calculated using the formula:

K _corr. = R _comp (MgCl ₂ ) / R _comp (norm, str.), Where (MgCl ₂ ) is the compressive strength of specimens solidified in a 5% solution of magnesium chloride, R _comp (norm, str.) Is the compressive strength of the specimen, hardened under normal conditions (at a temperature of 20 ± 2 ° C and humidity ≥95%). The adhesion strength of the protective coating to the concrete base was carried out in accordance with GOST 31356-2007.

The adhesion strength and the coefficient of corrosion resistance of the raw mixture for the protective coating according to the invention was determined in comparison with the prototype. The results are presented in the table.

It was found that the adhesive strength increased by (35.0-36.0)% and the coefficient of corrosion resistance increased by 24%.

Claims (4)

Raw mix for a protective coating, including Portland cement, sand, limestone, a complex additive and water, characterized in that it contains sand with a fraction of 0.315 mm, magnesia limestone with a specific surface area, S _beats = 280 m ² / kg, is used as limestone, additionally contains metakaolin based on kaolinite clays with a specific surface area S _beats = 1300 m ² / kg, a mixture consisting of microsilica with a specific surface area S _beats = 2000 m ² / kg, a dry polycarboxylate polymer based on methacrylic acid with a bulk density D = 0.520 g / cm ³ and a pH value of pH = 6.0 and potassium formate with the following ratio of components, wt. %: specified microsilica 87.0-87.5 specified polycarboxylate polymer 4.1-4.3 potassium formate 8.4-8.7 with the following ratio of the components of the raw mixture, wt. %: Portland cement 44.5-46.3 specified sand 26.9-27.4 specified limestone 6.4-6.8 specified metakaolin 1.6-1.8 specified complex additive 4.8-5.1 water 14.0-14.4