RU2359935C2 - Chemical supplement to concrete mixtures and construction mortars - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: invention pertains to the area of construction materials, in particular, to compositions of complex supplements used in manufacture of concrete mixtures and construction mortars. Antifreezing chemical supplement to concrete mixtures contains, wt %: sodium thiosulphte - 10-77.7, sodium rhodanate - 10-77.7, sodium sulphate - 12.3-80.

EFFECT: enhanced early strength, secured freezing at temperatures as low as -15°C.

1 tbl, 1 ex

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 possibility of construction work in the winter, complex additives are introduced into the composition of concrete and mortar mixtures, which contribute to the hardening of cement at low temperatures.

A complex additive is known in concrete mixtures (Russian patent No. 1733422, IPC ⁶ С04В 18/02, priority 04/23/1990) 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, as an organic additive, dicarboxylic acid from the group: oxalic, dicarboxylic acid melt of the C ₃ -C ₆ fraction, pimelic acid in the following ratio of components, wt.%: A mixture of ballast salts of coke oven desulfurization based on thiosulfate and sodium thiocyanate is the basis, technical lignosulfonate - 9-13, the specified dicarboxylic acid - 3-5.

A disadvantage of the known complex additives is the presence in its composition of 13-18% of an organic component that helps to slow down the processes of structure formation in concrete and reduces the anti-frost effect of the additive. The closest in technical essence and the technical result achieved is a complex additive for concrete mix (AS USSR No. 1231030, IPC ⁵ С04В 24/20, publ. 05/15/86), containing sodium salts of benzenesulfonic acids and water, as well as additional sodium sulfate in the following ratio of components, wt.%: sodium salts of benzenesulfonic acids - 7.5-13.5; sodium sulfate - 6.5-12.5; water is the rest. In the composition of the specified complex additives, the content of the organic component is reduced to 7.5-13.5%.

However, the introduction of sodium salts of benzenesulfonic acids also helps to slow down the hydration of cement over time, especially in the early stages of hardening. Sodium sulfate helps to accelerate the formation of structure in the early stages of hardening, does not cause corrosion of the reinforcement.

The basis of the invention is the task of creating a chemical additive in concrete mixtures and mortars by increasing its effect on the early stages of structural formation by eliminating from the composition of an undesirable component that helps reduce the early strength of concrete, and additional inclusion in the composition of effective components that increase the early strength of concrete and allow conduct concreting in the winter.

The problem is solved in that the organic component is excluded from the complex additive in concrete mixtures and mortars containing sodium sulfate salts and according to the invention thiosulfate and sodium thiocyanate are introduced in the following ratio of components, wt.%:

sodium thiosulfate 10-77.7 sodium thiocyanate 10-77.7 sodium sulfate 12.3-80

Sodium thiosulfate due to the intensification of hydration processes helps to increase the solubility of cement minerals (increase the concentration of Ca ^{2+ ions} in suspension), shortens the hardening time and optimizes the ratio between gel and capillary porosity of concrete, as a result of which hardening processes are accelerated, early and final strength and frost resistance are increased concrete.

Sodium thiocyanate shortens the onset time of cementitious mortars and, in combination with sodium thiosulfate, provides both a slight increase in their mobility and a reduction in the curing time, as well as the possibility of hydration processes in concrete and cement mortars at low temperatures (up to -15 ° С). By changing the ratio of the amounts of rhodanide, thiosulfate and sodium sulfate in the aqueous solution of the additive, a balance is achieved between the plasticity, water demand and frost resistance of the concrete mixture, which results in an increase in the strength and early strength of concrete under normal hardening conditions and at low temperatures to -15 ° C. The composition of the claimed additives in small quantities can include both accompanying salts, which do not significantly affect the corrosion activity of cement mortars with respect to steel reinforcement and hydration processes during structural formation, and salts - hydration process inhibitors in the early stages of hardening and dispersants.

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

With an increase or decrease in the indicated amount of thiosulfate, sulfate and sodium thiocyanate in the composition of the additive, the strength of concrete decreases both during hardening under normal conditions and during hardening in frost.

The decrease in the content of sodium thiosulfate in the composition of the additive below the claimed limit leads to a decrease in the intensity of hardening of concrete, reducing its frost resistance. A decrease in the concentration of sodium thiocyanate leads to a significant increase in the time interval for the onset of hardening at low temperatures (to -15 ° C). Sodium sulfate within the claimed limits enhances the anti-frost effect of thiosulfate and sodium thiocyanate on the structure formation in cement mortars and accelerates the structure formation under normal hardening conditions.

An increase in the content of the mixture of salts of one of the components claimed as an additive above the claimed limit leads to a decrease in the effectiveness of its effect on hardening strength at normal and low temperatures due to weakening the interaction of components that enhance the antifrosty characteristics of the additive.

The use of a new composition and new concentration ratios in the proposed complex additive expands the scope of its application, for example, its use as an antifreeze.

The inventive complex additive is prepared as follows.

The additive is prepared by dosing and mixing aqueous solutions or dry salts of thiosulfate, rhodanide and sodium sulfate within the claimed amounts (it is possible to use a mixture of salts taking into account the adjustment of the chemical composition within the claimed limits). The components of the additive are mixed and dosed in an appropriate container for transportation to the consumer.

Example

To study the properties of the inventive additives, a concrete mixture was prepared containing: 1 part of cement, grade ШПЦ-III / А-400 (Kryvyi Rih cement plant); 1.9 parts of sand with a particle size modulus 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 as a saline solution with a concentration of 20-50% was introduced into the concrete mixture together with mixing water in an amount of 0.4-3% by weight of cement. The mobility of the concrete mixture was determined according to GOST 10181-2000, and it was OK≈4 cm.

For strength tests, concrete samples were prepared from the concrete mixture containing 1.5% additives by weight of cement, solidified at low temperatures and then 28 days under normal thermal and humid conditions, as well as concrete samples solidified under normal thermal and humid conditions. The strength of the samples was determined in accordance with GOST 18105-86. Concrete mixtures containing the additive were tested both in the claimed component ratios and beyond. Concrete samples made in accordance with the composition specified in the known solution (prototype) were also tested.

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

From the table it follows that the claimed complex additive provides a set of strength of concrete when hardening in frost to -15 ° C and then under normal conditions (experiments No. 4-11), and exceeding or lowering the maximum content of the declared components in the composition of the additive reduces the strength characteristics of concrete ( experiments No. 2-3, 12-13).

The proposed composition of the components allows you to get a new highly effective chemical additive that provides a set of strength of concrete during hardening in frost to -15 ° C.

Claims (1)

Antifrosty chemical additive in concrete mixtures and mortars containing sodium sulfate, characterized in that it further contains sodium thiosulfate and sodium thiocyanate in the following ratio, wt.%:
sodium thiosulfate 10-77.7 sodium thiocyanate 10-77.7 sodium sulfate 12.3-80