RU2410362C1 - Raw mixture used for obtaining nonautoclave-hardening aerated concrete - Google Patents

Abstract

FIELD: construction. ^ SUBSTANCE: raw mix for manufacturing of nonautoclave-hardening aerated concrete contains the following components, wt %: portland cement 28-38, filler - quartz-feldspar sandstones, ground down to specific surface of 2500-3000 cm2/g, 26-31, hydrate lime in the form of lime milk with density p=1.2 g/cm3 2-4, aluminium powder 0.02-0.1, water 22-39, plasticiser C-3 0.4-1.18, hemihydrate plaster 1.5-1.8, microsilica 2-3. ^ EFFECT: improved physical-mechanical characteristics of items made of aerated concrete of nonautoclave hardening, reduced consumption of cement component, widening of raw materials base. ^ 3 tbl, 1 ex

Description

The invention relates to compositions of raw mixtures used in the production of cellular concrete non-autoclave hardening, and can be used in the building materials industry to obtain cellular concrete heat-insulating and heat-insulating structural products of non-autoclave hardening.

Known raw mix for aerated concrete, including Portland cement, ground sand, aluminum powder, lime, alkylsulfanol, sodium chloride and water [Patent SU No. 682469, С04В 13/22, BI 32, 1978]. Its disadvantage is that the resulting cellular concrete has a reduced hydrophobicity and increased density.

A raw material mixture for cellular concrete was proposed, including mineral binder, thermolithic sand, aluminum powder and water [Patent No. 1377268, С04В 38/02, BI No. 8, 1988]. The disadvantage of this mixture is the large shrinkage and relatively low strength of cellular concrete products.

A known composition of aerated concrete mixture for the manufacture of aerated concrete containing Portland cement, lime, aluminum powder, calcium chloride, water [Patent SU No. 1491857, С04В 38/02, publ. in 1989]. The disadvantage of this composition is the content of a large amount of water - 56 ... 84% by weight of cement, which does not allow to achieve high strength non-autoclaved aerated concrete with a decrease in density. Corrosion of reinforcement and the possibility of efflorescence on products due to the presence of an increased amount of hardening accelerator — sodium chloride in the amount of 2-3.6% of the mass of cement, which limits the use of the known mixture, become inevitable.

Known raw mix [Patent RU No. 2062772, С04В 38/02, publ. in 1996], including Portland cement 28-50%, siliceous component 46.65-49.37%, C-3 superplasticizer based on sodium salts of the condensation product of naphthalene sulfonic acid with formaldehyde 0.28-0.5%, aluminum powder 0.07- 0.35%, ground hydrated cement. The main disadvantage of this composition is the increase in the cost of production due to the additional grinding of hydrated cement.

The proposed composition [Patent RU No. 2073661 C1, publ. in 1997], containing Portland cement 4.7-55%, lime 7.8-30%, ground zeolite 37-64%, aluminum powder 0.07-0.29%, superplasticizer C-3 0.13-1.2 % The disadvantage of this mixture is the additional cost of grinding lime and zeolite. In addition, the introduction of fine-milled zeolite in the composition of cellular concrete helps to accelerate the expansion and stabilization of the porous concrete mixture after expansion, while the processes of extinguishing lime are not yet fully completed, which leads to the formation of an uneven porous structure of the finished product and the deterioration of the operational properties of cellular concrete.

Closest to the technical nature of the proposed mixture is a mixture for the preparation of aerated concrete containing Portland cement (30.6-34.6 wt.%), Ash of thermal power plants (22.3-25.2 wt.%), Lime (2.68 -3.10 wt.%), Wood shavings of a fraction of 5 ... 200 mm (0.71-9.17 wt.%), Aluminum powder (0.04-0.045 wt.%), Water [Patent SU No. 1759819, IPC C04B, publ. 09/07/92]. The disadvantage of this mixture is the formation in the cellular concrete mixture of undesirable organic impurities released from concrete chips, which worsen the hardening of concrete due to biological corrosion and adversely affect the strength of the finished product.

The task of the invention is to improve the physico-mechanical characteristics of non-autoclaved aerated concrete products, reducing the consumption of cement component, expanding the raw material base through the use of filler - quartz-feldspar sandstone, crushed to a specific surface of 2500 cm ² / g

The solution to this problem is achieved by the fact that pre-quartz-feldspar sandstone, crushed to a specific surface area of 2500 cm ² / g, is subjected to chemical activation with hydrated lime (milk of lime density ρ = 1.2 g / cm ³ ) for 3-5 minutes, then silica fume, C-3 plasticizer, water, Portland cement, semi-aquatic gypsum, aluminum suspension are sequentially introduced in the following ratio of these components, wt.%:

Portland cement 28-38 Quartz-feldspar sandstones 26-31 Hydrated lime 2-4 Aluminum powder 0.02-0.1 Water 22-39 Plasticizer S-3 0.4-1.18 Semi-aquatic gypsum 1.5-1.8 Silica fume 2-3

The distinguishing feature of a mixture of porous structure is that as a filler is proposed to use ground to a specific surface 2500-3000 cm ² / g quartz-feldspar sands, microsilica and hemihydrate gypsum.

The use of quartz-feldspar sandstone containing porous-grained and semi-rounded grains with a rough surface as a cellular concrete filler favorably affects the mechanical adhesion of the filler particles with a binder, and strengthens the contact zone between the cement stone and the rough surface of the filler, which increases the strength characteristics of the finished product .

Quartz-feldspar sandstones are subjected to chemical activation with hydrated lime (milk of lime with a density ρ = 1.2 g / cm ³ ) for 3-5 minutes. A hydroxide film of lime, which even partially covers the surface of the filler grains, promotes the active formation of the smallest gas bubbles on the surface of the filler grains, which facilitates the process of porosity of the cellular concrete mixture and provides a more efficient gas-swelling reaction.

The introduction of silica fume into the composition of the cellular concrete mixture promotes the penetration and even distribution of the smallest particles of silica fume in the shell of calcium hydroxide on the surface of the grains of the filler, which activates the processes of chemical interaction of silica fume and calcium hydroxide with the additional formation of compounds of tobermorite group, strengthening the structure of cement stone and concrete in general.

Semi-aquatic gypsum, introduced into the raw material mixture to stabilize and harden the porous cellular concrete mixture, was calculated on the basis of the maximum binding of aluminates and calcium cement aluminoferrites to ettringite, which causes the expansion of the forming cement stone and reduces sedimentary phenomena.

Example

The proposed composition for aerated concrete is prepared as follows.

Preparation of raw materials is carried out in a separate way.

Quartz-feldspar sandstones are milled to a specific surface of 2500-3000 cm ² / g, which provides the necessary degree of disintegration of the crystals of the main sandstone minerals and the effective flow of gas-swelling processes of the cellular concrete mixture. Table 1 presents the average chemical composition of quartz-feldspar sandstone, table 2 shows their physical and mechanical properties.

The raw material mixture for aerated concrete is prepared according to the generally accepted method in a mixer by sequential mixing of quartz-feldspar sandstone, hydrated lime in the form of lime milk with a density ρ = 1.2 g / cm ³ , silica fume, plasticizer C-3, water, Portland cement, semi-aquatic gypsum, water and aluminum suspension.

To achieve the necessary conditions for the porosity of the aerated concrete mixture, we initially prepare a slurry consisting of hydrated lime, quartz-feldspar sandstones and 50% water (of the total amount of mixing water) with a temperature of 70-80 ° C, active mixing is carried out in a mixer for 5-7 minutes .

At the second stage, without stopping the stirrer, silica fume, C-3 plasticizer is added to the resulting slurry, which allows reducing the amount of mixing water without reducing the mobility of the mixture, then Portland cement, semi-aquatic gypsum are introduced to stabilize the porous process and reduce sedimentary phenomena and the remaining amount of water.

Then, a water-aluminum suspension is introduced into the prepared mixture, with continuous stirring of the mass for 2.5-5 minutes for uniform distribution of the blowing agent in the entire volume of the mixture. The temperature of the cellular concrete mixture during unloading is 40-45 ° C. The resulting mixture is poured into detachable, pre-lubricated and heated metal molds. After the expansion and gaining of the necessary stripping strength are completed, the products are removed from the molds and sent to the steaming chamber for heat and humidity treatment at atmospheric pressure and a temperature of 90 ° C according to the regime of 1.5- (6-8) - (1.5-2) hours.

To obtain aerated concrete according to the proposed composition of the cellular concrete mixture, mixtures with different content of components were prepared. Data on the composition of the mixtures and physico-mechanical properties of the samples of products obtained on their basis are presented in table 3.

An advantage of the proposed composition of the aerated concrete mixture is the introduction of a filler — quartz-feldspar sandstone, crushed to a specific surface of 2500-3000 cm ² / g into the molding composition. When using the specified filler containing grains that are most commensurate with the geometry of the interstitial partitions, dense and durable structures of the interstitial partitions and a uniform finely porous structure of aerated concrete with pore sizes withstand without defects are formed in the composition of the cellular concrete masses, which increases the strength characteristics of aerated concrete.

Active mixing of quartz-feldspar sandstone with hydrated lime (milk of lime with a density ρ = 1.2 g / cm ³ ) for 3-5 minutes leads to the formation of film coatings of calcium hydroxide on the surface of the grains, i.e. creates a sufficient alkaline environment, intensifying the process of expansion, over the entire volume of aerated concrete mixture.

Silica fume, introduced into the raw material mixture, interacts physically and chemically with lime released during the hydrolysis of alite and belite in Portland cement, as well as with hydrated lime introduced into the cellular concrete mass for chemical activation of the filler, forming an additional amount of high-strength low-basic calcium hydrosilicates with it. In addition, due to the effective compaction of inter-pore walls with finely divided silica fume, hardening of finished aerated concrete products occurs.

The addition of semi-aquatic gypsum provides the necessary stability (stability) and strengthens the porous cellular concrete system.

According to the test results, non-autoclaved cellular concrete products for various purposes with an increased level of operational properties, a compressive strength of 2.55-4.7 MPa were obtained and are recommended as effective building materials for heat-insulating and heat-insulating-structural purposes in the construction of various household and industrial facilities.

Claims (1)

The raw material mixture for the production of non-autoclaved aerated concrete, including Portland cement, filler, hydrated lime in the form of milk of lime with a density ρ = 1.2 g / cm ³ , aluminum powder, water, characterized in that it contains ground quartz feldspar sandstones, crushed to a specific surface of 2500-3000 cm ² / g, plasticizer C-3, semi-aquatic gypsum, silica fume in the following ratio of these components, wt.%:
Portland cement 28-38 Quartz-feldspar sandstones 26-31 Hydrated lime 2-4 Aluminum powder 0.02-0.1 Water 22-39 Plasticizer S-3 0.4-1.18 Semi-aquatic gypsum 1.5-1.8 Silica fume 2-3