RU2384538C2 - Complex additive for concrete and water mortars - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: complex additive into concrete and water mortars, containing a mixture of salts based on thiosulfate and sodium thiocyanate and technical lignosulfonates, according to invention, additionally contains polycarboxylates and organosilicon liquid at the following ratio of components, wt %: technical lignosulfonates - 5-29, polycarboxylates - 20-70, organosilicon liquid - 0.01-1.0, mixture of salts on the basis of thiosulfate and sodium thiocyanate - the rest.

EFFECT: improved mobility of concrete or water mortar and its preservation for a longer period of time, better strength and frost resistance of concrete.

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Description

The invention relates to the field of building materials, in particular to the compositions of complex additives used in the production of concrete mixtures and mortars.

To ensure the plasticity of concrete mixtures and mortars, an excess of water is introduced into their composition, which contributes to water separation and separation of solid components, and as a result, to a decrease in strength, frost resistance and other characteristics of concrete. To regulate the amount of mixing water, additives with plasticizing and water-reducing effects are introduced into the composition of concretes and mortars, which can accelerate the processes of structure formation and hardening, while ensuring the production of concrete mixtures and mortars with specified characteristics.

A complex additive is known in concrete mixtures (Ukrainian patent No. 23457, IPC ⁶ С04 В 13/24, publ. 08/31/1998) containing a mixture of ballast salts of coke oven gas desulfurization based on sodium thiosulfate and thiocyanate and an organic component. The known additive additionally contains sodium sulfate, and as an organic component - molten one stripped after alcohol distillery stillage in the following ratio of components, wt.%: A mixture of ballast salts of coke oven gas purification based on thiosulfate and sodium thiocyanate - 20-60, sodium sulfate - 10-15, molasses one stripped off alcohol bard - 30-65.

A disadvantage of the known complex additives is the increased content (30-65%) in its composition of the organic component in the form of one-off post-alcohol stillage stillage, which refers to plasticizers of medium efficiency. As a result of this, the known additive does not allow the maximum reduction of water.

The closest in technical essence and the achieved technical result is a complex additive for concrete mix, (AS USSR No. 1733422, IPC ⁵ С04В 28/02, СВВ 28/02 // 24: 04, 24:18, publ. 15.05. 92), containing a mixture of ballast salts based on sodium thiosulfate and thiocyanate, as well as technical lignosulfonates in an amount of 9-13%. The additive contains an additional organic component - dicarboxylic acid from the oxalic group, a dicarboxylic acid melt of the C ₂ -C ₆ fraction and pimelic acid in an amount of 3-5%.

As part of this complex additive, the concentration of the organic component is reduced to 12-18% without loss of plastic characteristics of cement-based building mixtures.

However, the addition of dicarboxylic acid slows down the hydration of cement, especially in the early stages of hardening, and does not allow the maximum water content in concrete to be reduced. Therefore, technical lignosulfonates are additionally used, which contribute to increasing the plasticity of the concrete mixture, but slow down the formation of structure in the early period of hardening, and do not provide increased strength, as well as frost resistance of concrete and mortar.

The basis of the invention is the task of creating a complex additive in concrete mixtures and mortars by removing a less effective plasticizing component and introducing new components into the composition, which increase both the plastic characteristics of concrete solutions and strength, as well as frost resistance of concrete.

The problem is solved in such a way that a complex additive in concrete mixtures and mortars containing a mixture of salts based on sodium thiosulfate and thiocyanate and lignosulfonates, respectively, the invention further includes polycarboxylates and organosilicon liquid in the following proportions of components, wt.%:

technical lignosulfonates 5-29 polycarboxylates 20-70 organosilicon liquid 0.01-1.0 a mixture of salts based on thiosulfate and sodium thiocyanate rest.

A mixture of salts based on sodium thiosulfate and thiocyanate due to the intensification of hydration processes increases the solubility of cement minerals and optimizes the ratio between gel and capillary porosity of concrete, resulting in faster hardening processes, as well as increased strength and frost resistance of concrete. Therefore, the inventive complex additive provides an increase in the strength of concrete. In addition, an organosilicon liquid in the presence of this mixture of salts turns into a gel, compacting the microstructure of the hardening system, additionally enhances the hydration activity of silica-containing minerals of Portland cement, reacts with hydrolysis of lime with the formation of tobermorite-like calcium hydrosilicates with fibrous morphology. Such a microstructure provides not only increased compressive strength, but also in bending, and, as a result, contributes to an increase in crack resistance and frost resistance.

Technical lignosulfonates are characterized by plasticizing properties. They reduce the surface tension at the water-cement interface due to adsorption on cement particles to form a thin layer of molecules.

Polycarboxylates increase the effect of technical lignosulfonates, provide a more complete and uniform spreading of water on the surface of cement particles, including microcracks, and play the role of a lubricant. A layer of water with technical lignosulfonates and polycarboxylates reduces adhesion between cement particles, which manifests itself as plasticization of a concrete mixture (increasing its mobility). The interaction of these two plasticizers in mortars disperses cement particles, which contributes to the completeness of the mass exchange between the reacting components. In addition, these plasticizers have a modifying effect on the growth form of the forming crystals of cement stone.

By introducing a complex of plasticizers, which consists of technical lignosulfonates and polycarboxylates in a mixture of salts based on sodium thiosulfate and thiocyanate, hydrophobizing organosilicon liquid, a balance is achieved between the plasticity and water demand of the concrete mixture, which ensures an increase in the mobility of the concrete mortar and its preservation for a longer period time, increasing the strength and frost resistance of concrete.

The optimal ratio of components in the composition of the additive was established experimentally.

When increasing or decreasing the specified number of plasticizers - technical lignosulfonates and polycarboxylates, as well as hydrophobizing organosilicon liquid in the composition of the additive, the strength and frost resistance of concrete decrease.

The exclusion of a mixture of salts based on thiosulfate and sodium thiocyanate from the composition of the additive (i.e., the lower limit of their content in the composition of the inventive additive is 0%) leads to a delay in setting time, a decrease in the intensity of concrete hardening and a decrease in frost resistance and ultimate strength. However, in the hot season for ready-mixed concrete, the delay in setting the concrete mortar to the time required to deliver it to the construction site is very important. In addition, the extension of the setting time of mortar concrete mixture is also relevant for the construction of large monolithic structures of hydraulic structures.

It is necessary to add that such plasticizers as technical lignosulfonates can be supplemented or replaced in the composition of the additive with such analogues as gluconates and the like, in amounts from 5 to 20% (wt.).

The increase in the content of the mixture of salts based on thiosulfate and sodium thiocyanate in the composition of the additive above the claimed border reduces its plasticizing effect.

The introduction of polycarboxylates can reduce the content of plasticizers of average efficiency - technical lignosulfonates, increase the effectiveness of the claimed additives on concrete mixes and mortars and expand its field of application.

A decrease in the amount of organosilicon liquid in the composition of the additive below the declared limits reduces the strength, frost resistance and survivability of concrete, and an increase significantly slows down the early structure formation. The inventive complex additive is prepared in the following way.

The additive is prepared by dosing and mixing a mixture of salts based on sodium thiosulfate and thiocyanate, technical lignosulfonates, polycarboxylates and organosilicon liquids within the declared amounts. The components are mixed and dosed in an appropriate container.

Example

To study the properties of the inventive additives, a concrete mixture was prepared containing: 1 part of cement of mark ШПЦ-III / А-400 (Kryvyi Rih cement plant); 1.9 parts of sand with a size module of 1.48; 2 parts of crushed stone fractions 5-10; 3 parts of crushed stone fractions 10-20; 0.43 parts of water.

The inventive additive was added to the concrete mixture with mixing water in an amount of 0.4 - 1.5% by weight of cement. The mobility of the concrete mixture was determined according to GOST 10181-2000.

Concrete samples were prepared from the concrete mixture, hardening under normal thermal and humid conditions, for testing for strength and frost resistance. The strength of the samples was determined respectively according to GOST 18105-86, and frost resistance - GOST 10060.0-95. Concrete mixtures containing the additive were tested both with the claimed ratio of components and with their beyond quantitative proportions. Concrete samples were also tested, made in accordance with the composition specified in the known solution (prototype), hardened under normal thermal and humid conditions.

The compositions of complex additives according to the known and claimed solutions, as well as the physico-mechanical characteristics of concrete samples are presented in table 1.

From the table it follows that the claimed complex additive provides an increase in the ductility, strength and frost resistance of concrete (experiments No. 3-10), and when exceeding or decreasing the boundary content of the components in the composition, the strength and frost resistance of concrete decreases (experiments No. 2, 11).

The proposed composition of the components allows you to get a new highly effective complex additive, providing increased mobility of the concrete, mortar and its preservation for a longer time, increasing the strength and frost resistance of concrete.

Claims (1)

A complex additive in concrete mixtures and mortars containing a mixture of salts based on sodium thiosulfate and thiocyanate and technical lignosulfonates, characterized in that it further includes polycarboxylates and organosilicon liquid in the following ratio, wt.%:
technical lignosulfonates 5-29 polycarboxylates 20-70 organosilicon liquid 0.01-1.0 a mixture of salts based thiosulfate and sodium thiocyanate rest