RU2276121C1 - Composition of mixture for production of the non-autoclave gas concrete - Google Patents

Abstract

FIELD: construction materials industry; production of construction materials made out of the gas concrete.

SUBSTANCE: the invention is pertaining to the field of construction materials industry, in particular, to production of construction materials made out of the gas concrete and may be used at fabrication of the hardware products applied for construction and the heat-insulation of the residential, office and industrial buildings and structures. The technical result of the invention is simplification of composition of the gas concrete mixture, stabilization of its porosity formation process, acceleration of the processes of the cement hydratation and formation of the strong structure of the inter-pores partitions ensuring production of the non-autoclave gas concrete with the low density and heightened strength. The mixture composition for production of the non-autoclave gas concrete containing the portland cement, the aluminum powder suspension, the suspension produced by mixing of the semiaquatic gypsum with water, the aqueous solution of alkali and water in addition contains the fibrillar additive, and the mixture contains in the capacity of the alkali water solution the 30-40 %-s' solution of the sodium hydroxide and the suspension gained by mixing of gypsum with water in the ratio of gypsum to water equal to 1:10, at the following ratio of the components (in mass %): portland cement - 57-59, aluminum powder - 0.02-0.21, sodium hydroxide - 0.07-092, semiaquatic gypsum - 0.04-0.53, the fibrillar additive - 0.29, water - 40-41. The non-autoclave gas concrete products produced out of the indicated mixture in the form of the blocks, the plates of the various dimensions may be used in the capacity of the heat-insulating materials or the heat-insulating structural materials at building of the different objects of the residential and industrial use.

EFFECT: the invention ensures simplification of the gas concrete mixture composition, stabilization of its porosity, production of the heat-insulating materials or the heat-insulating structural materials of the low density and heightened strength, which may be used at construction of the different residential and industrial objects.

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Description

The invention relates to the field of production of building materials and can be used in the manufacture of products used for the construction and insulation of residential, administrative and industrial buildings and structures.

The known composition of the raw mix for the preparation of aerated concrete, which allows to reduce the average density and thermal conductivity, as well as to increase the biological resistance of aerated concrete. This mixture, including sodium liquid glass (6.6-9.1 wt.%) And aluminum powder (0.25-0.38 wt.%), Additionally contains caustic alkali (4.2-5.4 wt.%) ), ground expanded clay (15.6-16.0 wt.%), semi-aqueous calcium sulfate (3.3-4.5 wt.%), acetone (0.1-0.5 wt.%) and ground glass. The main disadvantage of this invention is the production of cellular concrete products of fairly high average density and low strength [Patent RU 2164504, class 7 C 04 V 38/02, 2001].

The composition of the raw mix for producing non-autoclaved aerated concrete is also known, including cement, a siliceous component, a surfactant, a plasticizer, and water. Sodium aluminate, polyamide fibers 3-5 mm long are additionally introduced into this mixture as a stabilizer, in the following ratio of components, wt.%:

Cement 43-90 Siliceous component 5-45 Surfactant 1-2 Sodium Aluminate 0.75-2.5 Plasticizer 0.5-1.5 Indicated fibers 2.75-6.0 Water up to W / T 0.25-0.6

The main disadvantage of this composition of the non-autoclaved aerated concrete mixture is that pre-synthesized sodium aluminate is introduced into the mixture as a stabilizer. An essential feature of the synthesis of sodium aluminate is that at the time of formation it is in a colloidal, gel-like state, from which it passes into a crystalline state within a short time. Therefore, introducing it into the composition of the aerated concrete mixture in a pre-synthesized form does not give the expected positive effect in the formation of the microstructure and strength of the inter-pore walls of aerated concrete. In addition, during crystallization, sodium aluminate binds up to six moles of water, and therefore the pre-synthesized sodium aluminate already contains this water and does not bind it in the composition of the aerated concrete mixture when it is porous. The stabilization of this process according to the known composition is achieved through the use of a fairly scarce S-3 superplasticizer and a relatively large amount of polyamide fiber additive [Patent RU 2226517, cl. 7 C 04 V 38/02, 2004].

The closest to the proposed composition is the composition of the mixture for the manufacture of autoclaved aerated concrete, including Portland cement, a suspension of aluminum powder, milk of lime, gypsum in the form of a suspension in water in a ratio of 1: 1.63-7, silica fume, calcium chloride, mixing water at the ratio of components, wt.%:

Portland cement 51-71, Aluminum powder 0.01-0.15, Lime 0.04-0.7 Semi-aquatic gypsum 0.1-0.4 Silica fume 0.6-3.5 Calcium chloride 0.5-3, Water Rest

[Patent RU 2209801, cl. 7 C 04 V 38/02, 2003]. The main disadvantage of this composition is the following. The introduction of lime mortar into the gas-concrete mixture does not accelerate the porization process: the beginning of the process occurs no earlier than 10 minutes after mixing, the need for an increased temperature of the mixture is about 45-50 ° C, the formation of compounds that do not contribute to increasing the stability of the mixture - calcium hydroaluminates, which are also negative affect the strength of the inter-pore septum and the array as a whole.

The objective of the present invention is to simplify the composition of the aerated concrete mixture, stabilize the process of its porization, accelerate the hydration of cement and the formation of a strong structure of inter-pore walls, providing non-autoclaved aerated concrete with low density and high strength.

The problem is achieved in that the composition of the aerated concrete mixture, including Portland cement, a blowing agent - aluminum powder, a fibrous additive and water, is additionally introduced an aqueous solution of sodium hydroxide and a suspension of semi-aquatic gypsum in the following ratio, wt.%:

Portland cement 57-59 Aluminum powder 0.02-0.21 Sodium hydroxide 0.07-0.92 Semi-aquatic gypsum 0.04-0.53 Fiber additive 0.29 Water 40-41.1

Example. For the manufacture of products from an aerated concrete mixture of the proposed composition, a mixture of Portland cement, water and a fibrous additive of basalt or polymer fiber with a fiber diameter of 3-10 μm and a length of 3-7 mm is separately prepared, an aluminum suspension in an aqueous solution of sodium stearate, 30-40% hydroxide solution sodium and gypsum suspension, which is obtained by mixing molding or building gypsum with water in a ratio of gypsum: water = 1: 10. To prevent setting, the gypsum slurry is mixed for 20 minutes.

The amount of water needed to prepare a solution of sodium hydroxide, aluminum and gypsum suspensions is part of the total amount of water that is needed to prepare the aerated concrete mixture.

Aerated concrete mixture is prepared in the following sequence. In a mixture of cement, fibers and water continuously mixed from the moment of mixing, first a solution of calcium hydroxide is added, then an aluminum suspension and, finally, a gypsum suspension is introduced. Each added component of the mixture is intensively mixed after being introduced into the aerated concrete mixture for 30 seconds. The prepared aerated concrete mixture is poured into pre-heated to 35-40 ° C molds, in which products are molded during the process of porous mixing. After pouring the mixture into molds, they are covered with plates of light heat-insulating material on top to reduce the heat loss necessary to stabilize the process of porosity and the hydration of cement and hardening of aerated concrete products. After 1.5-2 hours, when the products acquire the necessary formwork strength, they are removed from the molds and sent to a warm warehouse or steaming chambers to complete the hardening processes.

To obtain aerated concrete according to the proposed composition, mixtures with different content of components are prepared. Data on their composition and properties of the materials obtained are presented in the table. The test results confirm the possibility of obtaining from the proposed composition a mixture of products from aerated concrete with a wide range of properties in terms of density and increased strength.

The following can be attributed to the advantages of the proposed composition of aerated concrete mixture: the process of porization can be carried out at temperatures of 20-35 ° С; the possibility of obtaining aerated concrete products with low density and sufficiently high strength; the porization process is stabilized with the formation of the same spherical and polyhedral pores 1-3 mm in size; the resulting uniformly porous structure provides higher strength and improves the thermophysical properties of aerated concrete products. These effects are achieved by introducing components such as sodium hydroxide, fiber additives and gypsum into the mixture.

Sodium hydroxide in the composition of the aerated concrete mixture acts as an intensifier of the process of porous mixture due to more active interaction of aluminum powder with sodium hydroxide with the formation of sodium hydroaluminate. This compound is formed directly in a mixture in gel form and eventually crystallizes in the form of hexagonal crystals of a layered structure in interstitial septa. During crystallization, sodium hydroaluminate binds six moles of water and due to this, the amount of free water in the aerated concrete decreases rapidly, and after the gas evolution process ends, the mixture quickly sets, resulting in a stripping strength of the aerated concrete in a shorter time compared to the prototype. The transition of sodium hydroaluminate from the gel state to crystalline directly in the inter-pore septum increases the strength of both the septum and the entire product.

In the presence of gypsum, sodium hydroxide interacts with it with a partial formation of sodium sulfate, which is an accelerator of cement hydration and hardening processes. In addition, bivalve gypsum, in a colloidal state, reacts with the formed sodium hydroaluminate in gel form, resulting in the formation of sodium-containing calcium hydrosulfoaluminate, the structure of which is similar to calcium monohydrosulfoaluminate. The formation of this compound allows the formation of a denser and stronger inter-pore septum. Due to the formation of all the above compounds, the processes of cement hydration are intensified, the rate of cement hydration increases by 1.2-1.4 times, which contributes to an increase in the strength of aerated concrete.

The introduction of a polymer dispersion-reinforcing fiber into the aerated concrete mixture makes it possible to stabilize the process of mixture porosity due to the uniform distribution of fiber throughout the volume of the mixture during the formation of the gas phase. This fiber is placed in the resulting inter-pore septa and creates a spatial mesh frame that does not allow the mixture to settle during the expansion process.

In addition, polymer fibers, located in inter-pore partitions, reinforce them also by forming a spatial reinforcing mesh and thereby increase the strength of the entire hardened aerated concrete mass. In this case, the dispersed fiber plays the role of centers of recrystallization of the primary products of cement hydration.

The combined presence of these substances in the mixture of the proposed composition ensures the stability of the porous process and obtaining aerated concrete products with a strength of 0.40 MPa with an average density of 200 kg / m ³ and 4.0-6.0 MPa - 800 kg / m ³ , which exceeds the strength characteristics aerated concrete products of non-autoclave method of hardening of known compositions, as well as those specified in GOST 25485-89. The use of Portland cement of a higher grade, for example, grade M 500, gives an additional increase in the strength characteristics. In addition, due to the uniform and uniform pore structure, the thermal conductivity of the products from the mixture of the proposed composition is reduced.

The use of practically one Portland cement as a solid phase of an aerated concrete mixture is economically feasible in the manufacture of non-autoclaved aerated concrete, as this can significantly reduce the time required for building strength by using the high hydraulic activity of Portland cement and its ability to generate highly dispersed hydration products that are involved in the formation of rounded closed pores and strong interstitial septa.

Non-autoclaved aerated concrete products made of a mixture of the proposed composition in the form of blocks, plates of various sizes can be used as heat-insulating or heat-insulating and structural materials in the construction of various household and industrial facilities.

Table
The composition of the mixture for the manufacture of non-autoclaved aerated concrete The components of the mixture and the properties of the obtained material Content of components (wt.%) And level of properties Suggested composition Prototype one 2 3 four 5 6 Portland cement (M 400) 57.84 58.3 58.16 58.75 70 43 Aluminum powder 0.21 0.1 0.05 0.02 - - Sulfonate powder - - - - 1,5 2.0 Semi-aquatic gypsum 0.53 0.31 0.16 0.04 - - Sodium hydroxide 0.92 0.5 0.24 0,07 - - Sodium Aluminate - - - - 0.75 2,5 Plasticizer S-3 - - - - 1,5 1,5 Fiber additive 0.29 0.29 0.29 0.29 3,5 6.0 Water 40.21 40.50 41.10 40.83 33,2 22.0 Water-hard ratio 0.65 0.65 0.65 0.65 0.36 0.25 Bulk weight, kg / m ³ 200 300 500 800 250 1000 Compressive strength, MPa 0.4 0.70 1.83 5.25 0.87 11.0 Heat conductivity coefficient, W / m · ° С 0,050 0,062 0.116-0.128 0.160-0.185 - -

Claims (1)

The composition of the mixture for the manufacture of non-autoclaved aerated concrete, including Portland cement, a suspension of aluminum powder, a suspension obtained by mixing semi-aqueous gypsum with water, an aqueous solution of alkali and water, characterized in that it contains a suspension obtained by mixing semi-aqueous gypsum with water in a gypsum: water ratio of 1: 10, as an aqueous solution of alkali - 30-40% solution of sodium hydroxide and an additional fiber additive in the following ratio of components, wt.%: Portland cement 57-59 Aluminum powder 0.02-0.21 Sodium hydroxide 0.07-0.92 Semi-aquatic gypsum 0.04-0.53 Fiber additive 0.29 Water 40-41.1