RU2759255C2 - Composition and method for manufacturing heat-insulating concrete - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: group of inventions relates to the field of construction, namely to building materials, in particular heat-insulating concretes used in industrial, civil construction, as well as in industries of oil and gas production and transportation, as thermal insulation. A composition for the manufacture of heat-insulating concrete includes, by wt.%: cement 24.45-27.85, finely ground bentonite clay 24.45-27.85, foaming agent 0.30-0.75, colloidal nano-disperse sodium polysilicates with a silicate module 6.5 2-4, soil modifier “DS-35” 0.43-0.49, water 42.97-44.46. A method for manufacturing heat-insulating foam concrete from the above-mentioned composition includes filling of dosed dry finely ground Portland cement and bentonite clay into a forced mixing mixer for joint dry mixing for 3-4 minutes, sequential pouring of colloidal nano-disperse sodium polysilicate with a silicate module 6.5, previously made by introducing 16% silicon dioxide hydrosol into a 20% aqueous solution of sodium silicate at a ratio of 1:1.5 and mixing at 95°C for 1.5 h with an exposure of 0.5 h, and a solution of the “DS-35” modifier in water for wet mixing for 2-3 minutes until the formation of creamy mass, introducing foam for the final production of foam mass, its filling into molds, aging for 3 days and stripping.

EFFECT: technical result is a reduction in cement consumption, an increase in compressive strength and a decrease in the thermal conductivity of concrete.

2 cl, 4 tbl

Description

The invention relates to the field of construction, namely to building materials, in particular, heat-insulating concretes used in industrial, civil construction, as well as in the fields of oil and gas production and transportation, as thermal insulation.

Known foam concrete [1], obtained by mixing water, clay, cement and additives, lime in the amount of 1-3% of the volume of clay. Then the resulting solution is mixed with seawater in an amount of 1-2% by weight of cement and subsequent mixing with foam based on a foaming agent.

The disadvantage is the high consumption of used cementitious materials of lime and cement in aerated clay concrete, which increases the cost of the material. In addition, the content of lime and sea water in foam concrete leads to the release of alkali and insoluble salts on the surface of products during operation, i.e. the formation of white bloom of efflorescence. With periodic moistening, this reaction is repeated, leading to repeated leaching of the structural elements, therefore, a decrease in the strength of structural bonds.

Also known heat-insulating concrete [2] including cement, foaming additive, water, montmorillonite clay containing at least 60% of the mineral (Al, Mg) ₂ (OH) ₂ H ₂ O and as a foaming additive contains the additive "NIKA".

The disadvantage of the known heat-insulating concrete is the use of montmorillonite clay containing the mineral (Al, Mg) ₂ (OH) ₂ H ₂ O, which is a scarce and expensive material, as well as a high consumption of cement, which causes the high cost of heat-insulating concrete and limits its use.

The closest to the claimed technical solution in terms of a set of features (prototype) is heat-insulating concrete [3], including cement, ^{clay powder with a specific surface area of 1800-2000 cm 2} / g with a clay particle content of not more than 50%, a foaming agent based on alkyl sulfates with with a density of 1.0-1.2 g / cm ³ with the following ratio, wt%:

Cement 33.0-39.7 Clay powder 14.2-19.2 Foaming agent 0.30-0.75 Water 42.5-50.4

The disadvantage of the specified heat-insulating concrete is low strength with such a high content of cement in its composition. Due to the use of natural ground clay powder with a clay particle content of up to 50%, when the heat-insulating material is moistened, the clay particles in it hydrate and swell, which leads to the destruction of the foam structure of the material.

The technical result, which consists in eliminating these disadvantages, is achieved by the fact that heat-insulating concrete, including cement, clay powder, foaming agent and water, instead of clay powder, contains ground bentonite clay with a specific surface area of 2500-3000 cm ² / g and additionally colloidal nanodispersed sodium polysilicate with a silicate module 6, 5 and modifier "DS-35" with the following ratio of components, wt%:

Cement 24.45-27.85 Finely ground bentonite clay 24.45-27.85 Colloidal nanodispersed sodium polysilicates 2-4 Modifier "DS-35" 0.43-0.49 Foaming agent 0.30-0.75 Water, W / T 42.97-44.46

The method of manufacturing heat-insulating concrete from the above composition consisted in the fact that initially in laboratory conditions sodium polysilicates with a silicate modulus of 6.5 were made, which, according to US Pat. RF 2124475 (example 1), was obtained by introducing a 16% hydrosol of silicon dioxide into a 20% aqueous solution of sodium silicate at a ratio of 1: 1.5, by stirring at 95 ° C, for 1.5 h, followed by holding 0.5 h. Then the dosed dry finely ground components of various compositions (Table 1), consisting of Portland cement M 400 and finely ground bentonite clay to a specific surface area of 2500-3000 cm ² / g were poured into a forced mixing mixer for joint dry mixing for 3-4 minutes, after that, colloidal nanodispersed sodium polysilicates and a solution in water of the "DS-35" modifier were sequentially poured for wet mixing for 2-3 minutes. Further, with simultaneous stirring, a foam obtained from a foaming agent based on alkyl sulfates with a density of 1.0-1.2 g / cm was introduced into the made creamy mass for the final production of the foam mass. The final stage of the process is filling the foam mass into molds, holding for 3 days and stripping.

The chemical and mineralogical compositions of the used bentonite clay are shown in tables 2,3.

Whence it follows that the main constituent minerals are montmorillonite, quartz, clays, and some others. Here the leading place is occupied by montmorillonite. Therefore, the considered bentonite clays can be called montmorillonite, and the minerals composing them - minerals of the montmorillonite group. The more montmorillonite in the mixture, the higher its hydrophilicity, a feature of this type of clay. Also, this material is non-toxic and has good chemical resistance, therefore it is often used in many industries, including construction.

Colloidal nanodispersed polysilicates used as additives represent the transition region of compositions from liquid glasses to silica sols and are classified as nanomaterials.

The structural element of polysilicate is a silicon-oxygen tetrahedron, which is the main polymer component of polysilicates.

The main difference between polysilicates and liquid glasses (highly alkaline silicate systems) is their polymer form, which is silica particles ranging in size from 4 to 5 nm. The polymer form is 60% or more of the total silica content, which ensures high strength properties of the resulting gel structures. The efficiency of polysilicates is 4 times higher than the efficiency of liquid glasses - aqueous solutions of lump silicate, which allows the use of technological solutions with a lower concentration.

Additionally introduced into the composition of heat-insulating concrete modifier "DC-35" is an aqueous dispersion of vinyl acetate acrylic copolymer with a low-viscosity medium without solvents and plasticizers, obtained by polymerizing monomers in the liquid phase with a specific recipe. Physicochemical characteristics of this modifier are presented in table. 4.

On the basis of theoretical and experimental studies, a series of samples was made from the above proposed compositions and the method of the obtained foam mass in the form of cubes with dimensions of 10 × 10 × 10. The samples were tested for compressive strength and the thermophysical properties of the samples were determined. The data obtained are shown in Table 1. There are also given similar characteristics of the heat-insulating concrete-prototype.

The data obtained indicate that, with practically equal average density, the strength of samples from the proposed heat-insulating concrete is 60% higher than the strength of samples of a similar heat-insulating concrete prototype made from natural ground clay powder. In this case, the coefficient of thermal conductivity of the proposed heat-insulating concrete is 14% lower than similar indicators of the properties of the prototype. All this is due to the fact that:

- firstly, the bentonite clays we use belong to the montmorillonite group (smectites), therefore, they have almost all the properties of natural nanosized particles, which promotes active interaction with other components of the mixture, thereby forming heat-insulating concrete with high properties.

- secondly, colloidal nanodispersed sodium polysilicate particles actively reacting with free lime in Portland cement increases the strength of the cement stone, forming water-insoluble calcium silicates. The formation of analogous compounds with free oxides in bentonite clay is also not excluded. In addition, the polymeric form of sodium polysilicates, which makes up more than 60% of the total silica content, provides high strength properties of the resulting gel structures.

- thirdly, with the introduction of bentonite clay and a hydraulic binder into the mixture, the optimal ratio of the DS-35 modifier, the acrylic copolymer of which, reacting with chemically bound water in clay-forming minerals, forms chemically resistant and strong compounds that give the clay density, with the formation of a primary structural framework of double salts and hydrates and hydroxyl salts, with an increase in calcium hydrosilicates, and ultimately creating a stone-like material of very high strength, and very low water absorption capacity.

All this is due to the best joint interaction between fine particles of finely ground bentonite clay with Portland cement, nanodispersed particles of added additives and foam based on a foaming agent - alkyl sulfates with a density of 1.0-1.2 g / cm ³ .

In addition to improving the properties of the proposed heat-insulating concrete, the introduction of finely ground bentonite clay and additionally additions of colloidal nanodispersed sodium polysilicates and modifier "DS-35" into the composition, instead of crushed clay powder, and additionally additives, helps to reduce the consumption of Portland cement, and this generally leads to a decrease in the cost of heat-insulating material.

Sources of information

1. RF patent No. 2098391, C 04 B 38/10, publ. 1997 year

2. RF patent №2145586, С04В 38/10, published. 1999 year

3. RF patent №2234484, С04В 38/10, published. 08/20/2004

Claims (3)

1. Composition for the manufacture of heat-insulating concrete, including cement, foaming additive, clay powder and water, characterized in that it contains finely ground bentonite clay as a clay powder and additionally additives: colloidal nanodispersed sodium polysilicates with a silicate module 6.5, soil modifier "DS-35 "At the following ratio of components, wt.%: Cement 24.45-27.85 Finely ground bentonite clay 24.45-27.85 Colloidal nanodispersed sodium polysilicates 2-4 Modifier "DS-35" 0.43-0.49 Foaming agent 0.30-0.75 Water W / T 42.97-44.46 2. A method of manufacturing heat-insulating foam concrete from the composition according to claim 1, which consists in the fact that the metered dry fine-ground components according to the composition of the mixture: Portland cement and bentonite clay are poured into a forced mixing mixer for joint dry mixing for 3-4 minutes, after which they are sequentially poured colloidal nanodispersed sodium polysilicate with a silicate module 6.5, preliminarily prepared by introducing a 16% hydrosol of silicon dioxide into a 20% aqueous solution of sodium silicate at a ratio of 1: 1.5 and stirring at 95 ° C for 1.5 h with an exposure of 0.5 h, and a solution in water of the "DS-35" modifier for wet mixing for 2-3 minutes until a creamy mass is formed, then foam is introduced for the final production of foam mass, its filling into molds, exposure - 3 days and stripping.