RU2669898C1 - Hydrophobic granulated filler for concrete mixture, composition of concrete mixture for obtaining decorative concrete facade products, decorative concrete facade products - Google Patents

Abstract

FIELD: building.SUBSTANCE: group of inventions refers to the production of building materials and can be used to produce decorative concrete facade products hardening with heat and moisture treatment. Hydrophobizing granular aggregate for the concrete mix is made in the form of granules of 0.16–2.5 mm in size, consisting of a core and a shell, where the core is obtained by rolling with agitation in a paddle mixer of finely ground diatomite by spraying with a mixture of 50 % aqueous sodium hydroxide solution and an aqueous solution of sodium silicate at the following diatomite ratio, sodium hydroxide and aqueous sodium silicate solution: 0.67–0.82:0.09–0.165:0.09–0.165, and the protective shell is formed on the wet surface of the core by dusting in a dry pulverized mixture of a white portland cement with a pigment in a paddle stirrer, and then screening out the resulting granules and their spraying with ethyl-silicate-40 at the following ratio of white portland cement, pigment and ethyl silicate-40: 0.75–0.85:0.01–0.07:0.14–0.18. Concrete mixture for the manufacture of decorative concrete facade products includes, by mass.%: said filler 10–40, white portland cement 20–25, quartz sand 28–48, superplasticizer Polyplast SP-1 0.07–0.17, inorganic pigment 0.5–1.5, fibrous fiber 0.1–0.15, water – the rest. Decorative concrete facade product made from the said concrete mixture.EFFECT: increase frost resistance, compressive strength, stretching during bending and splitting.3 cl, 1 tbl, 1 ex

Description

The invention relates to the production of building materials and can be used to obtain decorative concrete facade products hardening during heat and moisture treatment.

Known concrete facade products obtained from concrete mixtures with a water-cement ratio of 0.2-0.4, where pre-ground to a specific surface of 3000-5000 cm ² / g mixture, wt. %: Portland cement 80-97; C-3 0.5-2.0; expanding additive 2.5-18. The resulting binder is mixed with sand, functional additives and mixing water. The mixture is molded "face down" by pouring concrete into molds and vibrating. The products are kept to a set of concrete stripping strength, and then carry out their stripping [Patent RU No. 2245784 C2, IPC B28B 1/14, 7/02, C04B 28/02, 7/52, publ. 02/10/2005, bull. No. 4].

It is known concrete building product with reduced thermal conductivity and water permeability, increased strength, obtained using granular composite aggregate. A granular composite aggregate for concrete products with a size of 0.5-10.0 mm, consisting of a core and a shell, where the core is obtained by granulating a mixture of co-milled to a specific surface of 150-250 m ² / kg of diatomite and sodium hydroxide in a mass ratio of 0.70 -0.95: 0.05-0.30 with a binder - an aqueous solution of sodium silicate with a density of 1.2-1.3 g / cm ³ in an amount of 0.1-7.0 wt. % of the mixture, and the shell is formed on the surface of the core by rolling it with a dry, dusty mixture of coarsely ground quicklime and sodium silicofluoride in a weight ratio of 0.85-0.95: 0.05-0.15, followed by hardening to a strength of at least 0.12 MPa, characterized in that after said pelletizing, an additional spraying of a 40% aqueous glyoxal solution is carried out in an amount of 1.0-8.0 wt. % (100% substance) by weight of the components of the shell. [Patent RU No. 2530816 C1, IPC С04В 20/00, СВВ 28/04, С04В 111/27, publ. 10/10/2014, bull. No. 28].

The disadvantages of the proposed solutions is the low strength of the products, the inability to obtain fine decorative products.

Closest to the proposed solution is a method for producing concrete building products and a concrete building product using hydrophobizing granular aggregate based on siliceous raw materials. Water-repellent granular aggregate for concrete, made in the form of granules consisting of a core and a shell, where the core is obtained by granulating a mixture of co-milled to a specific surface of 250-450 m ² / kg components: 1. flask or fly ash; 2. calcium stearate or GKZh-11 BSP, 3. sodium hydroxide, with a binder - an aqueous solution of sodium silicate. A protective shell is formed on the surface of the core by dusting in a dry dusty environment Portland cement or slag Portland cement, followed by hardening to a strength of at least 0.12 MPa. Concrete mixture for the manufacture of building products, includes wt. %: the specified placeholder 10-40; astringent 15-25; silica sand 30-50; Polyplast SP-1 0.05-0.15; water the rest. A method of obtaining concrete building products includes mixing the components of the above concrete mixture, molding building products, holding in molds and subsequent heat and moisture treatment of products at atmospheric pressure and a temperature of 70-90 ° C [Patent RU No. 2602436 C1, IPC C04B 20/00, C04B 28 / 04, С04В 40/02, C04B 111/27, publ. 11/20/2016, bull. No. 32].

The disadvantages of the concrete product according to the prototype is the low strength of the products, which reduces the durability of the structures, low decorative characteristics, in particular, the inability to obtain products with a wide range of colors. No attention has been paid to increasing frost resistance. Low water absorption does not allow for sufficient adhesion to the masonry mortar.

It is worth noting that in the production and use of decorative concrete facade products, one of the important conditions is to ensure high adhesion to the masonry mortar, which determines the integrity and durability of the finishing layer.

The problem to which the invention is directed, is to increase the compressive strength, tensile when bending and splitting, the adhesion to the masonry mortar (adhesion) and the frost resistance of the decorative concrete facade product using the developed hydrophobic granular aggregate.

This is achieved by the fact that: the hydrophobizing granular aggregate for the concrete mixture is made in the form of granules with a size of 0.16-2.5 mm, consists of a core and a shell, where the core is obtained by rolling with a stirrer in a paddle mixer of finely ground diatomite by spraying with a mixture of 50% aqueous an alkali solution with an aqueous solution of sodium silicate in the following ratio of diatomite, alkali-sodium hydroxide and an aqueous solution of sodium silicate: 0.67-0.82: 0.09-0.165: 0.09-0.165, and the protective shell is formed on a moist surface of the core by dusting in dry a dusty mixture of white Portland cement with pigment in a paddle stirrer, followed by screening the obtained granules and spraying them with ethyl silicate-40 in the following ratio of white Portland cement, pigment and ethyl silicate-40: 0.75-0.85: 0.01-0.07: 0 , 14-0.18. Concrete mixture for the manufacture of decorative concrete facade products includes hydrophobizing granular aggregate, binder, fine aggregate - quartz sand, water, superplasticizer - Polyplast SP-1, contains the above hydrophobizing granular aggregate as a binder, white Portland cement, inorganic pigment, fiber, in the following ratio of components, wt. %: hydrophobizing granular aggregate 10-40; white Portland cement 20-25; pigment 0.5-1.5; silica sand 28-48; Polyplast SP-1 0.07-0.17; fiber 0.1-0.15; water the rest. A decorative concrete facade product is obtained from the above concrete mixture.

To obtain a hydrophobizing granular aggregate used:

1) as core materials:

- silica component - diatomaceous fine powder Diasil (TU 5716-013-25310144-2008). The chemical composition, wt. %: SiO ₂ - 86.81; Al ₂ O ₃ - 5.91; Fe ₂ O ₃ - 2.67; MgO + CaO - 2.76; K ₂ O + Na ₂ O - 1.457; SO ₃ - 0.007; TiO ₂ 0.278; P ₂ O ₅ - 0.040; p.p.p. - 0.068. The specific surface area is 11.2 m / g.

- sodium hydroxide according to GOST 2263-79;

- an aqueous solution of sodium silicate (water glass) according to TU 2385-001-54824507-2000 with a density of 1.2-1.3 g / cm ³ ;

2) as shell materials:

- white Portland cement PCB 2-400-DO produced by the UNIS group of companies (Russia) according to GOST 965-89. White Portland cement without additives, 2 grades, grade 400. The compressive strength at 28 days of at least 39.2 MPa. Light reflection coefficient not less than 75%;

- inorganic pigment of Bayer concern (Germany) “Bayferrox” 610 (brown); synthetic iron oxide; the composition of Fe ₂ O ₃ 90-94%. SiO ₂ + Al ₂ 0 ₃ not more than 3%, loss on ignition not more than 4%; the average particle size of 0.1-0.6 microns; CAS number 1309-37-1 / 1317-61-9 / 51274-00-1, http://bayfeirox.com/en/products-applications-bfx/product-search/bayfe [accessed September 5, 2017];

- ethyl silicate-40 - a homogeneous mixture of oligoethoxysiloxanes according to GOST 26371-84, TU 2435-427-05763441-2004. The mass fraction of tetraethoxysilane is 10-15%, the mass fraction of silicon dioxide is 40-42%, the density at 20 ° C is 1.05-1.07 g / cm, and the optical density (400 nm) is not more than 1.4.

To obtain concrete mixtures with the specified hydrophobic granular aggregate used:

1. binder - white Portland cement specified above (p. 2);

2. inorganic pigment of Bayer concern (Germany) “Bayferrox” 610 (brown), indicated above (p. 2);

3. fine aggregate - construction quartz sand produced by Formaterialy LLC, Voronezh according to GOST 8736-93;

4. dispersed component - polyvinyl alcohol fiber made by Kuraray - Kuralon K II RESC 15/8, fiber diameter 38 microns, fiber length 8 mm, tensile strength 1600 MPa, bending strength 40 GPa, http: //www.kuraray .co.jp / kii / english / [accessed September 5, 2017];

5. Superplasticizer Polyplast SP-1 according to TU 5870-005-58042865-05;

6. tap water in accordance with GOST 23732-2011.

Example (table. 1, No. 1). Preparation of cores of hydrophobizing granular aggregate. An alkaline spray solution was prepared: 0.5 L of water and 0.5 kg of sodium hydroxide were mixed. Cooled to room temperature. To the solution was added 0.5 kg of an aqueous solution of sodium silicate. The resulting solution was sprayed with 2.5 kg of diatomite, which was mixed in a paddle mixer. The speed of rotation and the immersion depth of the mixer controlled the diameter of the resulting cores.

Obtaining a protective shell on the nuclei. After the formation of the granules, a mixture of 1.25 kg of white Portland cement with 0.025 kg of inorganic pigment was added to the mixer. The mixing process was continued without spraying in order to roll the casing. Then the remains of the mixture of white Portland cement and pigment were screened out on a sieve with a mesh size of 0.16 mm, and the resulting aggregate was evenly sprayed with 0.25 kg of ethyl silicate-40. The aggregate was aged for at least 1 day before use in the concrete mix.

Preparation of concrete mix. The dosage of the components was carried out by weight. The components were mixed in the mixer in the following order:

1. 9.65 kg of silica sand with 0.30 kg of pigment,

2.5.03 kg of white Portland cement

3. 2.01 kg of hydrophobizing granular aggregate,

4. 3.05 kg of water with 0.03 kg of superplasticizer - Polyplast SP-1 (previously dissolved in water);

5. 0.03 kg of fiber.

The process of forming products was accompanied by vibration. After 10 hours of preliminary hardening, the heat and moisture treatment of concrete samples was carried out in a steaming chamber at atmospheric pressure according to the regime of 2 + 6 + 2 hours and the temperature of isothermal exposure of 80 ° С, thus, the concrete mixture was prepared, the samples were molded and their heat and moisture treatment was performed according to the standard method [ Gershberg O.A. Technology of concrete and reinforced concrete products. - M .: Stroyizdat, 1971. - S. 98-102, 305-313].

The advantage of using the proposed hydrophobizing granular aggregate in the concrete mix is to increase the strength and frost resistance of concrete products. In contrast to the prototype, in the proposed technical solution, the alkaline activity of diatomite is preserved up to the moment of heat-moisture treatment of a decorative concrete facade product. This ensures the formation of a larger amount of a solution of sodium polysilicates during the reaction of diatomite and sodium hydroxide in the process of manufacturing products, and, consequently, leads to an increase in their strength and frost resistance as a result of uniform impregnation with the above solution. Upon receipt of the hydrophobizing granular aggregate of the prototype, the joint grinding of silica raw materials and sodium hydroxide leads to a partial reaction of the interaction of SiO ₂ and NaOH due to an increase in temperature in the volume of the mixture, which negatively affects the reactivity of the hydrophobizing granular aggregate during heat and moisture treatment of concrete.

When mixing the concrete mixture with fiber, an additional amount of air is drawn into its volume, which ensures the formation of a uniformly distributed micro- and nanoporosity, which acts as a damper when water freezes in the bulk of the material.

During the heat-moisture treatment of the product in the core of the aggregate, a reaction occurs between the silica and alkaline components with the formation of a solution of sodium polysilicates, which through the protective shell of the hydrophobizing granular aggregate enters the concrete matrix, impregnates it and imparts hydrophobic properties. The presence of ethyl silicate-40 in the shell of a hydrophobizing granular aggregate helps to cure the sodium polysilicate solution after heat and moisture treatment of a decorative concrete facade product, increasing its strength and frost resistance. The system “sodium polysilicate-ethyl silicate-40 solution” is distributed in the volume of the concrete matrix, settles on the surface of the pores and voids of the final product, hydrophobizing them, which protects the product from excessive water circulation.

The introduced fiber increases the resistance to cracking of the material, which allows it to withstand a greater number of freeze-thaw cycles without loss of strength. The formed porosity also provides better adhesion of the masonry mortar to the product.

The obtained samples were determined strength according to GOST 10180, adhesion strength (adhesion) according to GOST 31356, frost resistance according to GOST 10060.

Analysis of the test results of the properties of samples of concrete building products (Table 1) showed that the use of the developed water-repellent granular aggregate, white Portland cement, pigment, silica sand, SP-1 Polyplast, fiber and water in the concrete mix according to the proposed technical solution (in the above ratios) allows to obtain concrete building products with high strength: compressive, tensile when bent, tensile when cracked, adhesion (adhesion); frost resistance. The best results in terms of compressive strength, tensile strength during bending, tensile strength when cracking, adhesion strength (adhesion), frost resistance are observed in samples No. 1 and No. 2. Compared with the prototype, the compressive strength of the sample of composition No. 1 is increased by 8%, composition No. 2 - by 2%. The values of tensile strength in bending, tensile strength during cracking, adhesion strength (adhesion), frost resistance are not indicated for the prototype, however, the achieved results for compositions No. 1 and No. 2 exceed the performance of products presented in other technical solutions. Samples of compositions No. 3 and No. 4 in their characteristics are significantly worse than the prototype. The decrease in the number of hydrophobizing granular aggregate less than 10 wt. % does not provide sufficient impregnation of the matrix with a solution of sodium polysilicates, which is unfavorable for facade products, since it does not provide sufficient protection against migration of atmospheric moisture, and as a result reduces frost resistance and durability. The increase in the amount of granular aggregate more than 40 wt. % leads to an increase in the porosity of the composite, and, consequently, a decrease in strength. Varying the content of inorganic pigment within 2-7.5% by weight of white Portland cement in the composition of the shell of the hydrophobizing granular aggregate, as well as in the composition of the concrete mix for the facade product, allows its color to be varied. The decrease in fiber content of less than 0.1 wt. % of the mixture does not lead to the formation of sufficient porosity, which reduces the frost resistance of the products and adhesion to the masonry mortar, does not provide a sufficient increase in the strength of the products, which requires an increase in their thickness to provide sufficient strength for operation. The increase in fiber content above 0.15 wt. % of the mixture increases the voidness of products and negatively affects the appearance, the structure of the product is uneven, physical and mechanical characteristics are reduced.

Using the proposed technical solution allows to obtain the following positive results:

1. Improving frost resistance.

2. Improving the interaction of products with masonry mortar, ie, adhesive strength (adhesion).

3. Improving the decorative characteristics of the product, obtaining a wide palette of their colors. A mixture of “white Portland cement - pigment” should be used not only as a binder, but also as a shell material of hydrophobizing granular aggregate.

4. Increasing the strength, flexibility of products and providing the ability to achieve a low thickness of products without cracking to expand their areas of use.

5. Reducing labor and energy intensity, simplifying the production technology of hydrophobizing granular aggregate and final products based on it through the use of finely divided diatomite upon receipt, as well as a paddle mixer instead of a granulator.

6. The use of polyvinyl alcohol fiber is most favorable for an alkaline medium formed during the reaction in the core of a hydrophobizing granular aggregate and bulk impregnation of a concrete product. The proposed fiber is resistant to UV radiation, which makes it possible to use it in facade products.

Thus, the presented technical solution in the form of a hydrophobizing granular aggregate and concrete mixes makes it possible to obtain a decorative concrete facade building product with a compressive strength of 52-55 MPa, a tensile strength in bending of 4.2-6.2, an adhesion strength of 3.5- 3.7 MPa and a brand for frost resistance of 200-300 cycles.

The resulting decorative concrete facade product for industrial and civil construction is characterized by high adhesion to masonry mortar, as well as improved strength characteristics and frost resistance, which is especially important in the production of thin-walled concrete products operated outdoors in a humid environment and determines the integrity and durability of the finishing layer.

Claims (4)

1. Hydrophobic granular aggregate for concrete, made in the form of granules with a size of 0.16-2.5 mm, consisting of a core and a shell, characterized in that the core is obtained by rolling with stirring in a paddle mixer of finely ground diatomite by spraying with a mixture of 50% an aqueous solution of alkali with an aqueous solution of sodium silicate in the following ratio of diatomite, alkali - sodium hydroxide and an aqueous solution of sodium silicate: 0.67-0.82: 0.09-0.165: 0.09-0.165, and the protective shell is formed on a wet surface dusting kernels in a dry pulverized mixture of white Portland cement with a pigment in a paddle mixer, followed by sieving the obtained granules and spraying them with ethyl silicate-40 in the following ratio of white Portland cement, pigment and ethyl silicate-40: 0.75-0.85: 0.01-0.07: 0.14-0.18. 2. Concrete mixture for the manufacture of decorative concrete facade products, including hydrophobizing granular aggregate, cement, fine aggregate - quartz sand, water, superplasticizer - Polyplast SP-1, characterized in that it contains hydrophobizing granular aggregate according to claim 1, as a binder - white Portland cement, inorganic pigment, fiber, in the following ratio, wt.%: hydrophobizing granular aggregate 10-40 white portland cement 20-25 pigment 0.5-1.5 quartz sand 28-48 Polyplast SP-1 0.07-0.17 fiberglass 0.1-0.15 water rest 3. A decorative concrete facade product, characterized in that it is obtained from the concrete mixture according to claim 2.