RU2552274C1 - Method to prepare gypsum cement pozzolan composition - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: method to produce a gypsum cement pozzolan binder includes hydraulic activation of portland cement with surfactants for 1 minute with subsequent addition of gypsum and pozzolan component and repeated hydraulic activation for 2 minutes in a rotor-pulsation device with speed of shaft rotation of at least 5000 rpm, surfactants are a mixture of aqueous solution of carboxylate polyester "Glenium Ace® 430", a controller of setting and hardening times "BEST-TB" and a homogeneous mix of oligoethoxysiloxanes "Ethyl silicate -40" at the ratio of 1:0.17:0.07, he pozzolan component is metakaolin with hydraulic activity of at least 1000 mg/g at the following ratio of components, wt %: calcined gypsum 56.7-57.4, portland cement 14.6-15.4, specified surfactant 1-1.8, metakaolin 2.7-3.3, water - balance.

EFFECT: increased frost resistance, longer times of composition setting, giving it self-compacting property, increased strength, higher water resistance and reduced water absorption.

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Description

The invention relates to the field of building materials industry and can be used in the production of mixed binders based on gypsum and Portland cement.

A known method of preparing a raw mix for building products, including the mechanical activation of a gypsum cement binder with additives and water (RU 2044714 C1, IPC С04В 28/14, publ. 09/27/1995).

The disadvantage of this invention is the absence in its composition of a pozzolanic component (active mineral supplement), with the exception of the part contained in Portland cement. This, depending on the type of cement and the gypsum-cement ratio, can lead to the formation of ettringite, which creates internal stresses in the structure of the hardened stone, which leads to a decrease in the tensile strength of products with long-hardening. In addition, the short setting time of the mixture reduces the time of its viability, which complicates the manufacturing process of products.

The closest solution in technical essence and the achieved result to the present invention is a method for producing a binder, including the hydroactivation of Portland cement in the presence of a surfactant for 2-8 minutes in the activator with the addition of semi-aqueous gypsum and spent silica gel in the resulting mixture and mixing a mixer (RU 2368580 C2, IPC С04В 11/30, publ. 09/27/2009).

The disadvantages of this method are the complex implementation technology, which consists in activating Portland cement in a hydroactivator and mixing the gypsum-cement-pozzolanic composition in a mixer. Products obtained by this method have low frost resistance. The high cost of silica gel, as well as the instability of its characteristics, which affect the homogeneity of the rheological, physico-mechanical and other properties of the gypsum-cement-pozzolanic composition. The use of high-quality Portland cement (M600) significantly increases the cost of finished products. In addition, in the description of the above method, the test results of the samples for bending, water absorption are not shown, the setting time of the mixture is not indicated.

The objective of the invention is to increase the pot life of the finished composition, increase the bending and compression strength properties, frost resistance and water resistance of the hardened gypsum-cement-pozzolanic composition based on low-quality semi-aquatic gypsum and Portland cement of general construction grade M400, while simplifying the manufacturing technology.

The technical result of the invention is to increase frost resistance, lengthen the setting time of the composition, impart self-sealing ability to it, increase the flexural and compressive strengths, increase water resistance and reduce water absorption of the hardened gypsum-cement-pozzolanic composition.

The result is achieved in that in the method for producing a gypsum-cement-pozzolanic composition comprising the hydroactivation of Portland cement in the presence of a surfactant, adding semi-aquatic gypsum and a pozzolanic component to the resulting mixture, and mixing to a homogeneous mass, according to the invention, the hydroactivation is carried out in a rotary pulsation apparatus with a shaft rotation speed of at least 5000 rpm, while the Portland cement with surfactant is hydroactivated for 1 min, then gypsum and pozzolanic are added to component and re-activate for 2 minutes, as a surfactant, use a mixture of an aqueous solution of polycarboxylate ether "Glenium Ace® 430", the setting and hardening terms "BEST-TB" and a homogeneous mixture of oligoethoxysiloxanes "Ethylsilicate-40" in a ratio of 1: 0 , 17: 0.07, metakaolin with a hydraulic activity of at least 1000 mg / g is used as the pozzolanic component in the following ratio of components, wt.%:

Semi-aquatic gypsum 56.7-57.4 Portland cement 14.6-15.4 Specified Surfactant 1-1.8 Metakaolin 2.7-3.3 Water rest

The use of an aqueous solution of polycarboxylate ether “Glenium Ace® 430” as a surfactant reduces the water demand of the composition and increases the strength characteristics of products, the use of the setting time and hardening regulator “BEST-TB” increases the pot life of the finished composition, which is expressed in lengthening the setting time. The combination of these aqueous polycarboxylate ester solutions with a setting and hardening time regulator gives the gypsum-cement-pozzolanic composition a self-sealing ability. The use of a homogeneous mixture of oligooethoxysiloxanes “Ethylsilicate-40” in the surfactant helps to form the optimal pore structure of hardened stone, reduces water absorption and increases the water resistance of the finished product.

The use in the composition of the surfactant of the above components in the specified ratio leads to a synergistic effect and allows you to achieve the desired technical result.

For the manufacture of gypsum-cement-pozzolanic composition used the following materials:

Semi-aquatic gypsum brand G6BII manufactured by LLC "Arakchinsky gypsum" (GOST 125-79);

Portland cement PC 400 DON Volsky plant;

As a pozzolanic additive, metakaolin with a hydraulic activity of at least 1000 mg / g (TU 5729-098-12615988-2013). For the preparation of samples, metakaolin with a hydraulic activity of 1238 mg / g was used;

Tap drinking water that meets the requirements of GOST 23732.

As part of the surfactant used:

- an aqueous solution of polycarboxylate ether "Glenium Ace® 430" manufactured by LLC "BASF Building systems";

- regulator of setting and hardening terms - “BEST-TB”, manufactured by Innovative Technologies LLC. "BEST-TB" refers to the superplasticizers of the first group and is a copolymer based on carboxylic acid esters with the addition of a dark brown phosphate component with a density (at 20 ° C) of 1.24 g / cm ³ , mass fraction of dry matter 20-30 %;

- a homogeneous mixture of oligooethoxysiloxanes "Ethylsilicate-40" manufactured by JSC "Khimprom", Novocheboksarsk (TU 2435-427-05763441-2004).

Surfactants are prepared by mixing these components in the indicated proportions.

The invention is carried out as follows:

The amount of mixing water was selected from the conditions for ensuring normal density of the gypsum-cement-pozzolanic composition according to GOST 23789-79. To obtain samples used surfactants of the following composition, wt.%: An aqueous solution of polycarboxylate ether "Glenium Ace® 430" - 81.1; regulator of setting and hardening terms “BEST-TB” - 13.5; a homogeneous mixture of oligoethoxysiloxanes "Ethylsilicate-40" - 5,4.

In the working rotary pulsation apparatus, the calculated amount of water is poured into which a previously prepared surfactant is added. Then a weight dosage of Portland cement is carried out and its hydroactivation is carried out in a rotary pulsation apparatus with a shaft rotation speed of at least 5000 rpm for 1 min in the presence of a surfactant, then semi-aquatic gypsum and metakaolin are added to the resulting mixture and further hydroactivation is carried out in a rotary pulsation apparatus until smooth for 2 minutes

From gypsum-cement-pozzolanane compositions were made samples - beams with dimensions 4 × 4 × 16 cm.

After 28 days of normal hardening, the samples were subjected to mechanical tests. The strength of the hardened samples, water absorption, and also the setting time of the gypsum-cement-pozzolanic test were determined in accordance with GOST 23789-79. Frost resistance of products was determined in accordance with GOST 7025-91. The water resistance of the samples was determined by their softening coefficient equal to the ratio of compressive strengths of dry samples to water-saturated ones. The ability of a gypsum-cement-pozzolanic mixture to occupy the entire volume of the mold with the formation of smooth surfaces under its own weight without additional external influences was taken as a criterion of self-sealing ability.

Samples were also made according to the prototype on the basis of Portland cement for general construction purposes of the M400 brand.

The compositions of the gypsum-cement-pozzolanic composition are shown in table 1, the results of mechanical testing of the samples are shown in table 2.

The test results of the samples of gypsum-cement-pozzolanic composition according to the prototype based on Portland cement of general construction grade M400 are shown in table 2.

From the above data it follows that the maximum compressive and bending strengths are achieved when the content of semi-aquatic gypsum is in the range of 56.7-57.4%, Portland cement is 14.6-15.4%, surfactant is 1-1.8%, metakaolin with hydraulic activity of at least 1000 mg / g 2.7-3.3%. With the introduction of surfactants in an amount of less than 1%, there is a decrease in the indices of the investigated properties compared with the claimed limits. With the introduction of surfactants in an amount exceeding 1.8%, the investigated properties of the gypsum-cement-pozzolanic composition increase slightly.

Products obtained according to the invention have high strength characteristics, water resistance and frost resistance, low water absorption. The use of this surfactant allows you to get a self-compacting gypsum-cement-pozzolanic composition and increase its pot life.

In addition, the manufacture of a gypsum-cement-pozzolanic composition in one apparatus, as well as the use of low-grade semi-aquatic gypsum and Portland cement of general construction grade M400 make it possible to simplify the process of manufacturing products and reduce their cost.

Claims (1)

A method of obtaining a gypsum-cement-pozzolanic composition, comprising the hydroactivation of Portland cement in the presence of a surfactant, adding semi-aqueous gypsum and a pozzolanic component to the resulting mixture and mixing to a homogeneous mass, characterized in that the hydroactivation is carried out in a rotary pulsation apparatus with a shaft rotation speed at least 5000 rpm, while the hydroactivation of Portland cement with a surfactant is carried out for 1 min, then gypsum and pozzolanic component are added and repeated g reactivation for 2 min, as a surfactant, use a mixture of an aqueous solution of polycarboxylate ether “Glenium Ace® 430”, a setting and curing time regulator “BEST-TB” and a homogeneous mixture of oligoethoxysiloxanes “Ethylsilicate-40” in a ratio of 1: 0.17: 0 , 07, metakaolin with a hydraulic activity of at least 1000 mg / g is used as the pozzolanic component in the following ratio of components, wt.%:
Semi-aquatic gypsum 56.7-57.4 Portland cement 14.6-15.4 Specified Surfactant 1-1.8 Metakaolin 2.7-3.3 Water rest