RU2550630C1 - Method to prepare gypsum cement pozzolan binder - 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 carboxylate polyester "Odolit-K", a controller of setting and hardening times "BEST-TB" and water emulsion of octyltriethoxysilane "Penta®-818" at the ratio of 1:0.23:0.07, the pozzolan component is metakaolin with hydraulic activity of at least 1000 mg/g at the following ratio of components, wt %: calcined gypsum 57-57.7, portland cement 14.9-15.3, specified surfactant 1.3-1.8, metakaolin 2.7-3.3, water - balance.

EFFECT: increased frost resistance, longer times of mixture 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 C04B 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 in a mixer (RU 2368580 C2, IPC C04B 11/30, publ. September 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 mixture, increase the flexural and compressive strength properties, frost resistance and water resistance of the hardened gypsum-cement-pozzolanic binder (GSPV) based on low-grade semi-aquatic gypsum and Portland cement for general construction purposes, grade M400, while simplifying the manufacturing technology.

The technical result of the proposed solution is to increase frost resistance, lengthen the setting time of the mixture, give it self-sealing ability, increase the tensile strengths in bending and compression, increase water resistance and reduce water absorption of hardened gypsum-cement-pozzolanic binder.

The result is achieved in that in the method for producing a gypsum-cement-pozzolanic binder, including 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 Ponent and re-activate within 2 minutes, as a surfactant use a mixture of carboxylate polyester "Odolit-K", the setting time and hardening terms "BEST-TB" and an aqueous emulsion of octyltriethoxysilane "Penta®-818" in a ratio of 1: 0.23 : 0.07, metakaolin with a hydraulic activity of at least 1000 mg / g is used as the pozzolanic component, in the following ratio, wt.%:

Semi-aquatic gypsum 57-57.7 Portland cement 14.9-15.3 Specified Surfactant 1.3-1.8 Metakaolin 2.7-3.3 Water rest

The use of the Odolit-K carboxylate polyester as a surfactant reduces the water demand of the mixture and increases the strength characteristics of the products, the use of the setting time and hardening regulator “BEST-TB” increases the pot life of the finished mixture, which is expressed in lengthening the setting time. The combination of these carboxylate polyesters with a setting and hardening time regulator gives the gypsum-cement-pozzolanic mixture a self-sealing ability. The use of the Penta®-818 octyltriethoxysilane aqueous emulsion as a part of 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 mixture used the following materials:

semi-aquatic gypsum brand G6BII produced by Arakchinsky gypsum LLC (GOST 125-79);

Portland cement ПЦ 400 Д0 Н 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:

- Odolit-K carboxylate polyester manufactured by Service-Group LLC (TU 5745-01-96326574-08);

- the regulator of the 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 %;

- an aqueous emulsion octyltriethoxysilane "Penta®-818" manufactured by "Penta An ITW Company» - viscous 50% aqueous emulsion octyltriethoxysilane density of 1000 kg / m ^3, the content of active substance of 50%.

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 mixture according to GOST 23789-79. To obtain samples used surfactants of the following composition, wt.%: Carboxylate polyester "Odolit-K" - 76.92; the regulator of setting and hardening terms "BEST-TB" - 17.95; Pentyl®-818 aqueous octyltriethoxysilane emulsion - 5.13.

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 made and its hydroactivation is carried out in a rotary pulsation apparatus with a shaft rotation speed of at least 5000 rpm for one minute in the presence of a surfactant, then semi-aquatic gypsum and metakaolin are added to the resulting mixture and further mixing is carried out in a rotary pulsation apparatus until smooth for 2 minutes.

From gypsum-cement-pozzolnan mixtures, samples were made - 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 mixture are shown in table 1, the results of mechanical testing of the samples are shown in table 2.

The test results of samples of gypsum-cement-pozzolanic mixture 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 57-57.7%, Portland cement is 14.9-15.3%, surfactants are 1.3-1.8%, 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 1.3%, there is a decrease in the indices of the studied 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 binder increase slightly.

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

In addition, the manufacture of gypsum-cement-pozzolanic binder in one unit, as well as the use of low-grade semi-aquatic gypsum and Portland cement for general construction purposes, grade M400, simplify the process of manufacturing products and reduce their cost.

Claims (1)

A method of producing a gypsum-cement-pozzolanic binder, including the hydroactivation of Portland cement in the presence of a surfactant 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 of 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 a second guide is made activation for 2 minutes, as a surfactant, use a mixture of the Odolit-K carboxylate polyester, the BEST-TB set-hardener and the Penta®-818 octyltriethoxysilane aqueous emulsion in the ratio 1: 0.23: 0.07 , as a pozzolanic component, metakaolin with a hydraulic activity of at least 1000 mg / g is used, with the following ratio of components, wt.%:
Semi-aquatic gypsum 57-57.7 Portland cement 14.9-15.3 Specified Surfactant 1.3-1.8 Metakaolin 2.7-3.3 Water rest