RU2368579C1 - Additive for modification of gypsum binders - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: additive for modification of gypsum binders, construction mortars contains the following components, wt %: construction gypsum 65.0-75.0, Portland cement 24.0-28.0, microsilica 2.0-4.0, superplasticiser 0.7-1.2, redispersed polymer 0.8-1.2, regulator of setting and hardening time 0.04-0.06. Additive in the form of setting and hardening time regulator may contain tartaric acid.

EFFECT: accelerated hardening, higher water resistance, reduction of shrink deformations of cement stone.

2 cl, 3 ex

Description

The invention relates to the field of building materials, namely, additives used in the production of gypsum binders, mortars and concrete based on them.

Known additive selected as the closest analogue for the modification of gypsum binders, mortars and concrete based on them, including, by weight. %:

hydraulic binder 50-90 active mineral component 10-45 plasticizer 0.1-2 setting time adjuster and hardening 0.001-1 stabilizer 0.001-5

Moreover, as a hydraulic binder, the additive contains Portland cement of any kind, white cement, non-ferrous cement, alumina cement, hydraulic lime or a mixture thereof in any proportion, as an active mineral component - fly ash, ash or buckwheat husks, ashes and slag of thermal power plants, ceramic dust, waste products from brick and other ceramic products, aluminum compounds, fine quartz sand, silica fume, pumice, glass break, silica gel, tuff, diatomite, white soot, aerosil, or any mixture thereof proportions, as a plasticizing additive - a superplasticizer containing compounds based on sulfonated melamine-formaldehyde compounds and / or complexes based on them, compounds based on sulfonated naphthalene formaldehyde compounds or complexes based on them, compounds based on modified lignosulfonates, or compounds based on water-soluble carboxylate polymers, or their mixture in any proportion, as regulators of the setting time and hardening - a moderator of gypsum hardening, as the stabilizer - water-soluble cellulose ether. In this case, one of the following components or semi-aquatic gypsum or anhydrite mixed in any proportion is used as gypsum binders, the dosage of the additive is carried out in an amount of 10-40% of their mass, and its specific surface area is 550-7000 m ² / kg (RF Patent for invention No. 2260572, CL IPC С04В 11/30, publ. September 20, 2005, Bull. No. 26).

The disadvantage of this additive is that when it is used in the hardened material, water-insoluble polymer films are not formed, leading to increased water resistance of the material, and cellulose esters used in it slow down the process of hardening of gypsum or cement and reduce the rate of concrete strength gain. In addition, the use of a large amount of Portland cement in combination with silica fume leads to an increase in shrinkage deformations and the possibility of cracking. Moreover, the components of this additive do not have antiseptic properties, which, if stored for a long time, can lead to the penetration of microorganisms harmful to human health and destructive to the finished material.

The technical result of the claimed invention is to obtain additives for the modification of gypsum binders, which increases water resistance and gives slight shrinkage deformation of the hardened material without cracks obtained on its basis, at the required hardening speed and the strength of the solution, which has antiseptic properties. In other words, the result of the claimed invention is to obtain additives for the modification of gypsum binders with improved physical and mechanical properties.

The technical result is achieved by the fact that the additive for modifying gypsum binders, mortars, including hydraulic binders - Portland cement, the active mineral component - silica fume, plasticizing additive - superplasticizer, setting and hardening terms, additionally contains gypsum building and redispersible polymer, while components have the following ratio, wt.%:

gypsum building 65.0-75.0 Portland cement 24.0-28.0 silica fume 2.0-4.0 superplasticizer 0.7-1.2 redispersible polymer 0.8-1.2 setting and setting times 0.04-0.06

And also because it contains a redispersible polymer as the main organic additive.

And also the fact that as a regulator of the setting time and hardening contains tartaric acid.

The claimed additive for the modification of gypsum binders, mortars contains: building gypsum - 65.0-75.0 wt.%, Portland cement of any kind (for example, white cement or alumina cement) - 24.0-28.0 wt.%, Silica fume - 2.0-4.0 wt.%, Superplasticizer - 0.7-1.2 wt.%, Redispersible polymer - 0.8-1.2 wt.%, Tartaric acid - 0.04-0.06 wt. .%.

In the composition of this mixture, building gypsum is the main astringent component, providing a rapid increase in the strength of the finished mixture.

Portland cement in combination with silica fume ensures compaction of hardened material, increases its water resistance and durability.

Silica fume reacts with calcium hydroxide Ca (OH) ₂ , which is released during the hydration of Portland cement, with the formation of an additional amount of calcium hydrosilicates, which compact the structure of the hardened material.

Superplasticizer of melamine formaldehyde (SMF) or naphthalene formaldehyde (SNF) type increases the plasticity of the mixture and allows to reduce the amount of mixing water with stirring. The decrease in water in the composition of the mixture leads to a decrease in porosity, an increase in the strength and water resistance of the hardened material.

Redispersible polymer based on a copolymer of vinyl acetate and ethylene reduces permeability, increases the water resistance and elasticity of the hardened material. The use of a redispersible polymer with a hydrophobic effect leads to a higher water resistance of the hardened material, however, it somewhat reduces the rate of its hardening.

The setting and hardening time controller increases the life time of the material in the plastic state and allows you to increase the time period between mixing the mixture and its packing in the manufacture of products and building structures. The following substances can be used as a regulator of the setting time and hardening:

- high molecular weight organic compounds acting as protective colloids: animal glue, casein, gelatin, molasses, protein breakdown products, animal waste hydrolysis products, tannins, etc .;

- substances that reduce the solubility of gypsum: glycerin, alcohol, acetone, acids (citric, acetic, boric, lactic) and their salts;

- substances that affect the structure of gypsum: calcium acetate, calcium carbonate, magnesium carbonate.

Most preferred tartaric acid and keratin retarder for use as a setting and setting time regulator.

The introduction of the mixture with stirring an additional amount of air-entraining or foaming additives in the amount of 0.03-0.05 wt.% Allows to obtain material of different densities for use in bearing (low-porosity, high-strength) or heat-insulating (high-porosity, low-strength) products and structures.

In this case, the hardened material has the following main characteristics:

density 800.0-1100.0 kg / m ³ compressive strength not less than 4.0 MPa water absorption no more than 18% water resistance coefficient not less than 0.85 frost resistance not less than 25 cycles of freezing and thawing

The claimed additive for the modification of gypsum binders, mortars is illustrated using the following examples.

Example 1

To experimentally confirm the composition of the additive, the following mixture of ingredients was prepared (wt.%):

1. Plaster of construction - 80.

2. Additive for the modification of gypsum binders, mortars - 20.

3. Mixing water until the mixture is spreadable (mobility according to Suttard after 5 minutes - 250, after 10 minutes - 150, after 15 minutes - 90).

In this case, an additive was used to modify gypsum binders, mortars of the following composition (% by weight):

gypsum building 70 Portland cement 26.46 silica fume 2.0 superplasticizer melamine formaldehyde (SMF) type 0.7 redispersible polymer based on copolymer vinyl acetate and ethylene 0.8 wine acid 0.04

The resulting composition has the following physical and technical characteristics: density - 800.0 kg / m ³ ; water resistance coefficient - 0.86; compressive strength (28 days) - 4.9 MPa; frost resistance 30 cycles; the hardening and curing rate of the solution is 30 minutes, while for the 3-month storage period at a relative humidity of 80% and ambient temperature, ranging from 0 to 25 degrees Celsius, no microorganisms were found in the additive.

Example 2

To experimentally confirm the composition of the additive, the following mixture of ingredients was prepared (wt.%):

1. Plaster of construction - 80.

2. Additive for the modification of gypsum binders, mortars - 20.

3. Mixing water until the mixture spreads (mobility according to Suttard after 5 minutes - 250, after 10 minutes - 200, after 15 minutes - 90).

In this case, an additive was used to modify gypsum binders, mortars of the following composition (wt.%):

gypsum building 69 Portland cement 27.15 silica fume 2.1 superplasticizer melamine formaldehyde (SNF) type 0.8 redispersible polymer based on vinyl acetate copolymer and ethylene 0.9 wine acid 0.05

The resulting composition has the following physical and technical characteristics: density - 1000.0 kg / m ³ ; water resistance coefficient - 0.95; compressive strength (28 days) - 5.5 MPa; frost resistance 37 cycles; the hardening and curing strength of the solution is 40 minutes, while for the 3-month storage period at a relative humidity of 80% and ambient temperature, ranging from 0 to 25 degrees Celsius, no microorganisms were found in the additive.

Example 3

To experimentally confirm the composition of the additive, the following mixture of ingredients was prepared (wt.%):

1. Plaster of construction - 80.

2. Additive for the modification of gypsum binders, mortars - 20.

3. Mixing water until the mixture spreads (mobility along Suttard after 5 minutes - 250, after 10 minutes - 250, after 15 minutes - 90).

In this case, an additive was used to modify gypsum binders, mortars of the following composition (wt.%):

gypsum building 68 Portland cement 27.84 silica fume 2.2 superplasticizer melamine formaldehyde (SMF) type 0.9 redispersible polymer based on a vinyl acetate copolymer and versatic acid vinyl ester 1,0 keratin retarder 0.06

The resulting composition has the following physical and technical characteristics: density - 1100.0 kg / m ³ ; water resistance coefficient - 0.98; compressive strength (28 days) - 5.5 MPa; frost resistance 39 cycles; the hardening and curing strength of the solution is 45 minutes, while for the 3-month storage period at a relative humidity of 80% and an ambient temperature ranging from 0 to 25 degrees Celsius, no microorganisms were found in the additive.

When developing additives for the modification of gypsum binders, mortars, along with the specified strength, average density and thermal conductivity, you can also change the formwork strength from 20 minutes to 5 hours. This can significantly reduce the time required for erecting building envelopes without increasing the number workers.

The high efficiency of using modified gypsum binders is also achieved in the production of small wall porous concrete blocks for building envelopes. The turnover of molds increases 3-4 times, there is no need to use special equipment for drying and hardening of traditional building materials. Decrease in terms of a set of stripping strength increases the efficiency of construction work.

As can be seen from the above examples, the additive for the modification of gypsum binders, mortars increases the water resistance with slight shrinkage deformation of the hardened material obtained on its basis, at the required hardening speed and strength gain of the solution, in addition, the claimed additive has high antiseptic properties, in addition The introduction of silica sand in the additive reduces the possibility of crack formation.

Claims (2)

1. An additive for modifying gypsum binders, mortars, including a hydraulic binder - Portland cement, an active mineral component - silica fume, a plasticizing additive - superplasticizer, setting and hardening time regulator, characterized in that it additionally contains gypsum building and redispersible polymer, while components have the following ratio, wt.%:
gypsum building 65.0-75.0 Portland cement 24.0-28.0 silica fume 2.0-4.0 superplasticizer 0.7-1.2 redispersible polymer 0.8-1.2 setting and setting times 0.04-0.06. 2. The additive according to claim 1, characterized in that as a regulator of the setting time and hardening contains tartaric acid.