RU2228306C1 - Complex additive for concrete mixes and building mortars - Google Patents

Abstract

FIELD: manufacture of building materials. SUBSTANCE: additive contains 61-95% of mixture of ballast salts obtained during desulfurization of coke gas and based on sodium thiosulfate and thiocyanate and organic component, in particular superplasticizer. Additive can be used, in particular, for ferroconcrete items. EFFECT: activated structurization in early curing phases and increased strength and frost resistance of concrete in early curing phases. 1 tbl

Description

The invention relates to the field of building materials, in particular to the compositions of complex additives used in the production of concrete, mortar, reinforced concrete and special concrete products.

It is known that S-3 superplasticizer is used as an additive in concrete mixtures (see Ukraine No. 24298 A dated September 28, 1993, publ. 10/30/1998, M. Cl. ⁶ C 04 B 7/04, 28 / 04). Superplasticizer C-3 (sodium polynaphthalene sulfonate) is added to the concrete mixture in an amount of 1.35-1.65 by weight of cement. The known additive causes an increase in the plastic properties of the concrete mixture with a reduced water content, which prevents its separation during transportation, and also helps to seal the dispersed phase and reduce the air pore volume in the contact zone to obtain high-density concrete.

However, concrete mix with the addition of S-3 superplasticizer is characterized by insufficiently high strength in the early stages of hardening. It was experimentally established that the strength of such concrete is 11.5 MPa, and to obtain 70% of the grade strength of concrete, 120 hours of hardening are necessary, which lengthens the formwork. This is explained by the following.

C-3 superplasticizer as a high molecular weight compound (a product of polycondensation of naphthalenesulfonic acid and formaldehyde) forms an adsorption layer on the surface of cement particles and reduces the surface tension at the water-cement interface, which leads to the high resistance of the concrete mixture to delamination and its ductility at low water content. But it is the formation of a strong structured adsorption layer that prevents water loss, which leads to an extension of the hardening time of the concrete mixture.

In addition, the known concrete mixture containing the C-3 superplasticizer does not provide concrete with high frost resistance due to the increased content of capillary pores, since under the action of water freezing in them concrete structures are destroyed.

The closest in technical essence and the achieved technical result to the claimed additive is a complex additive in concrete mixtures and mortars containing a mixture of ballast salts of coke oven gas desulphurization based on sodium thiosulfate and thiocyanate and an organic component (see Ukraine No. 23457 A dated 28.12. 1996, published on August 31, 1998, M. Cl. ⁶ C 04 B 13/24).

The known additive additionally contains sodium sulfate, and as an organic component - Mellas stripped after alcohol distillery distillery in the following ratio of components, wt.%:

Mixture of ballast salts of desulfurization

thiosulfate-based coke oven gas

and sodium thiocyanate 20-60

Sodium Sulfate 10-15

One molasses

post-alcohol bard 30-65

The known additive does not provide high strength concrete in the early stages, which does not allow to carry out stripping work in the early stages. In addition, the known additive does not provide concrete products with high frost resistance. This is due to the increased water content of the concrete mixture to provide the necessary ductility and high capillary porosity of concrete products. In addition, due to the high content of sodium sulfate in the composition of the known additives, the corrosion resistance of the resulting concrete products is reduced.

The basis of the invention is the task of creating a complex additive in concrete mixtures and mortars, which due to the new combination of components and their new ratio provides activation of structure formation in the early stages, as well as optimization of the ratio between capillary and gel porosity in cement stone, which allows to increase the strength of concrete in the early stages of hardening and frost resistance of concrete products obtained.

The problem is solved in that in the known complex additive in concrete mixtures and mortars containing a mixture of ballast salts of coke oven gas desulphurization based on sodium thiosulfate and thiocyanate and an organic component, new according to the claimed invention is that the additive contains sodium polynaphthalene sulfonate as an organic component in the following ratio of components, wt.%:

Mixture of ballast salts of desulfurization

thiosulfate-based coke oven gas

and sodium thiocyanate 61-95

Sodium polynaphthalene sulfonate C ₃ Else

Between the totality of the essential features of the claimed invention and the achieved technical result there is the following causal relationship.

A mixture of ballast salts of coke oven gas desulfurization, containing thiosulfate, thiocyanate and sodium sulfate, accelerates the hardening of the concrete mixture by intensifying the development of hydration processes. Sodium polynaphthalene sulfonate (C-3 superplasticizer) is characterized by high plasticizing properties due to a decrease in surface tension at the water-cement interface, but it slows down the hardening process of the concrete mixture. The introduction into the concrete mixture of an additive containing a mixture of ballast salts of coke oven gas desulphurization based on sodium thiosulfate and sodium thiocyanate and sodium polynaphthalene sulfonate in the claimed ratio leads to an increase in concrete strength in the early stages of hardening and frost resistance of concrete products while maintaining high plasticity of the concrete mixture. This is explained by the following.

Under the influence of ballast salts of coke oven gas desulfurization, the structure of sodium polynaphthalene sulfonate changes, the anions of these sodium salts break long chains in its structure, which, in turn, while maintaining high plasticizing properties of the additive for 3-4 hours, accelerates the hardening of the concrete mixture in the first - the third day. A mixture of ballast salts of coke oven gas desulfurization based on sodium thiosulfate and sodium thiocyanate and sodium polynaphthalene sulfonate form an organomineral complex that increases the solubility of cement minerals, which leads to the formation of gel crystalline hydrates and, therefore, the acceleration of early hardening of the concrete mixture. The introduction of the inventive additives optimizes the ratio between capillary and gel porosity. It was experimentally established that the intense formation of gel porosity begins after 6 hours of hydration. By the third day of hardening, the ratio between capillary and gel porosity of cement stone is 46 and 54%, respectively. Due to this, when freezing concrete, the amount of ice formed decreases, the pore volume and the magnitude of the resulting stresses in concrete decrease, which leads to an increase in frost resistance of concrete products.

The claimed ratio of the mixture of ballast salts of coke oven gas desulfurization based on sodium thiosulfate and sodium thiocyanate and sodium polynaphthalene sulfonate in the composition of the additive is optimal and experimentally established.

The decrease in the content of the mixture of ballast salts of coke oven gas desulfurization based on thiosulfate and sodium thiocyanate in the composition of the additive below the claimed limit causes an increase in the early hardening time of the concrete mixture, which extends the formwork. This is explained by the inhibitory effect of sodium polynaphthalene sulfonate on the process of early hardening of concrete mixes. In addition, the frost resistance of the obtained concrete products is reduced by increasing capillary porosity.

The increase in the content of the mixture of ballast salts of coke oven gas desulfurization based on sodium thiosulfate and thiocyanate in the composition of the additive above the claimed limit leads to a decrease in frost resistance of concrete products and the plasticity of the concrete mixture.

The inventive additive is prepared as follows.

The components of the additive, namely a mixture of ballast salts of coke oven gas desulphurization based on sodium thiosulfate and sodium thiocyanate and sodium polynaphtha-lensulfonate (S-3 superplasticizer TU 2481-001-51831493-00), are dosed in the declared amount by weighing dosers of loose types AVJ, AVDC in corrosion -resistant performance. The components of the additive are mixed in a mixer with forced stirring and dosed in an appropriate container for transportation to the consumer.

To study the properties of the inventive additives, a concrete mixture was prepared containing 1 part concrete, 1.5 parts sand, 3 parts crushed stone fractions 10-20, 2 parts crushed stone fractions 10-40 and 0.38 parts water. To prepare the concrete mixture used:

- cement of Kryvyi Rih cement plant brand ШПЦ-III / А-400;

- Dnieper river sand with a particle size modulus of 1.48.

The inventive additive was previously dissolved and introduced into the concrete mixture with mixing water in an amount of 0.3-1.5% by weight of cement. In the resulting concrete mixtures, mobility was determined according to GOST 10181-2000. Concrete samples were prepared from concrete mixtures for testing for early strength, including at low temperatures, and frost resistance. To determine the time to reach 70% brand strength of samples aged from 24 hours, the compressive strength was determined in accordance with GOST 18105-86. After 28 days, the samples were tested for frost resistance according to GOST 10060.0-95. Concrete mixtures containing the additive were tested both with the claimed ratio of components and with the prohibitive ratio of the claimed components. The results of the tests are presented in the table. Tests were also carried out for a concrete mixture made in accordance with the prototype, as well as a concrete mixture containing 1.5% by weight of cement of the S-3 superplasticizer.

The table shows that the inventive additive according to the invention provides a simultaneous increase in the strength of concrete in the early stages, including at low temperatures, and frost resistance of the obtained concrete products while maintaining high ductility of the concrete mixture (experiments No. 2-6). By reducing the content of the mixture of ballast salts of coke oven gas desulfurization in the composition of the additive below the claimed amount, the early hardening of the concrete mixture increases and frost resistance decreases.

With an increase in the content of the mixture of ballast salts of desulfurization of coke oven gas in the composition of the additive above the claimed amount, the plasticity of the concrete mixture and the frost resistance of the product decrease.

Claims (1)

Complex additive in concrete mixtures and mortars containing a mixture of ballast salts of coke oven gas desulfurization based on sodium thiosulfate and thiocyanate and an organic component, characterized in that the additive contains C-3 superplasticizer in the following ratio, wt.%: Mixture of ballast salts of desulfurization thiosulfate-based coke oven gas and sodium thiocyanate 61-95 Superplasticizer S-3 Else