RU2258051C2 - Concrete mix modification method - Google Patents

Abstract

FIELD: manufacture of building materials.

SUBSTANCE: concrete mix is modified by introducing (i) aqueous solution of polymeric compounds with different molecular mass obtained by condensation of naphthalenesulfonic acid and formaldehyde and (ii) ferrous or ferric salts in amount 2-4% of the weight of mix, said polymeric compounds being used in amount 0.3-0.7% of the weight of cement in case of degree of polycondensation equal to 2-5 and at their ratio to water between 30:70 and 40:60. Iron salt is added after addition of above-indicated aqueous solution.

EFFECT: increased density and strength of concrete in early stages of process.

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Description

The invention relates to the production of building materials, and in particular to a method for preparing concrete when modifying additives, for example complex ones, are introduced into the concrete mixture.

Known concrete mixtures with complex additives modifying their properties (RU, No. 2078744, C 04 B 28/04, 1997).

Known concrete mixture containing (as a water-reducing surfactant) superplasticizer C-3 (RU, No. 2055034, C 04 B 28/02, 1996).

A known method of producing high-strength cellular concrete by sequential supply of a surfactant, water, cement to the mixture with the addition of plasticizer C-3 in an amount of 0.2-0.4% by weight of cement (RU, No. 2133722, C 04 V 38/10, 1999 )

A known method of preparing a concrete mixture with the addition of superplasticizers by pretreating cement with superplasticizer in an amount of 2.2-20% by weight of cement (RU, A1, No. 1812769, C 04 B 40/00, 1996).

A known method of preparing a concrete mixture by mixing cement and water with the subsequent introduction of superplasticizer in the form of a solution (RU, No. 20186885, 04 04 40/00, 1994).

A known aluminosilicate mixture containing a superplasticizer based on sodium salts of the condensation product of naphthalenesulfonic acid and formaldehyde in an amount of 0.05-0.3 wt.% In excess of 100% of the mixture (RU, No. 2165907, 04 04 28/06, 2001).

Known complex additive of concrete mixture containing superplasticizer C-3 based on the sodium salt of the condensation product of naphthalene sulfonic acid with formaldehyde in an amount of 85.21-89.74% (RU, No. 2041863, C 04 B 28/04, 1995).

Known raw mix for the preparation of heavy concrete, containing a superplasticizer based on sodium salts of the condensation product of naphthalene sulfonic acid with formaldehyde in an amount of 0.5-1% by weight (consumption) of cement (RU, No. 2100304, 04 04 28/00, 1997).

Known concrete mixtures and methods for preparing concrete in the presence of modifying additives help to maintain the mobility of the concrete mixture, remove air, and obtain concrete with low water content.

Known technical dispersant, which is a mixture of polymer compounds of different molecular weights, obtained by sulfonation of naphthalene followed by condensation with formaldehyde and neutralization with sodium hydroxide (RU, GOST 68481-79).

The known dispersant has a certain focus in use, namely, it is used as an auxiliary substance in the rubber, textile, leather, aniline-paint industry and in the production of synthetic rubber, in the production of chemical fibers and chemical-photographic industry.

There is a method of modifying a concrete mixture in the preparation of concrete from cement, sand, gravel, water and modifying additives, for example complex, by introducing modifying additives into the mixture in the form of polymer compounds of various molecular weights obtained by condensation of naphthalenesulfonic acid and formaldehyde (Collection of scientific papers, edited by Batrakova VG, Falikman VR "Research and use of chemical additives in concrete", M .: NIIIZhBD989. 20-23).

The closest analogue of the proposed invention is a method of modifying a concrete mixture by introducing an aqueous solution of polymer compounds of various molecular weights obtained by condensation of naphthalenesulfonic acid and formaldehyde and 2-4% by weight of a mixture of an iron salt of two or trivalent (RATINOV V.B. et al. Concrete Additives, Moscow, Stroyizdat, 1989, pp. 92,105,110,162-172).

This technical solution is taken as a prototype of the present invention. However, it has disadvantages.

High plasticizing properties are manifested in mixtures where the polymer compound has a higher polycondensation coefficient (n = 14-16), these compounds dilute the concrete mixture as much as possible, provide an increase in the density and strength of concrete due to better workability, lower air entrainment and a higher rate of loss of entrained air, however, high polycondensation leads not only to a strong dilution of the concrete mixture, but also to a significant slowdown in the setting time (in the first three days, the set of strength Twain slowed down), and the strength of growth begins in the already solidified samples. Plasticizing properties are much lower manifested in mixtures where the polymer compound has a lower polycondensation coefficient (n = 2-4), these compounds do not affect the strength characteristics, but provide acceleration of hardening of concrete in the early stages and improve its uniformity.

The present invention is based on the solution of the problem of accelerating the hardening of concrete in the early stages of the preparation process, while increasing the density and strength of concrete in the following stages:

- due to the dispersing properties of modifying additives;

- due to the use of polymer compounds with a low degree of polycondensation;

- through the use of a specific fractional composition of the polycondensation products of naphthalenesulfonic acid and formaldehyde;

- due to the introduction of compounds in the form of a solution;

- due to the introduction of complex additives;

- due to the optimal values of the amount of additives, their ratio in aqueous solution and low limits of the degree of polycondensation.

According to the invention, this problem is solved in a method of modifying a concrete mixture by introducing into it an aqueous solution of polymer compounds of various molecular weights obtained by condensation of naphthalene sulfonic acid and formaldehyde, and 2-4% by weight of a mixture of an iron salt of two or trivalent, these polymer compounds are used in an amount 0.3-0.7 wt.% From the mass of cement with a degree of polycondensation equal to 2-5, and with a ratio of them and water as / 30: 70 / - / 40: 60 / (%), respectively, and the indicated iron salt is introduced after specified water of solution.

Applicants have not established any sources of information that would contain information about technical solutions identical or equivalent to the claimed objects of the invention, each of which is characterized by the presence of a new set of features. This, according to the applicants, determines the compliance of the invention with the criterion of "novelty."

Due to the implementation of the distinguishing features of the invention (in conjunction with the features indicated in the restrictive part of the formula), important new properties of the object are achieved.

The implementation of the distinguishing features of the invention clearly determines the appearance of an important technical effect in the object, which consists in the fact that a polymer compound with a low degree of polycondensation is used as a dispersant in the preparation of concrete mixture, using the effect of increasing the surface energy of the dispersed system forming the concrete solution due to the attachment energy molecules used as an additive polymer compound in the early stages of its polycondensation, which in turn is essential It increases the surface energy of the dispersion, particularly the cement hydration period that promotes disaggregation coherent components of the mixture. The additive is introduced in the form of a solution in order to increase the mass of molecules, which is the main parameter that affects the development of the strength characteristics of concrete in the process of its preparation. In addition, the increase, therefore, the mass of the additive molecules compensates for the plasticizing properties of the concrete mixture in the early stages of curing while maintaining the effect of accelerated curing with the achievement of strength exceeding the standard to 30% or more. Subsequent introduction of a solution of iron salts enhances the achieved technical result.

Applicants are not aware of any publications that would contain information on the influence of the distinguishing features of the invention on the achieved technical result.

The above allows, according to the applicants, to recognize the claimed invention meets the criterion of "inventive step".

The method is as follows.

As additive (D), polymethylene polynaphthalene sulfonate Na is used with a degree of polycondensation of 2-5 in the form of an aqueous solution, in an amount of 0.4-0.7 wt.% By weight of cement, with its ratio of water as / 30-70 / : / 40-60 / (%).

As the dry components in the concrete mixture, cement M-400 / Ts /, quartz sand with Mkr> 2.0-2.2 / P /, crushed stone granite FR 5-20 mm / SH / are used.

Concrete mixtures are prepared while maintaining a given mobility (OK = 15 cm) and an unchanged amount of dry components C, P, U in them.

EXAMPLE 1

Determine the change in fluid flow from the amount of additive. The data are shown in table 1 "Dynamics of fluid flow".

From table 1 it is seen that a decrease in fluid flow relative to the control by 13.3% is observed when using additives of 0.4% (by weight of cement); the largest decrease in fluid flow relative to the control by 14.9% is observed when using additives of 0.5% and 0.6% (by weight of cement);

the smallest decrease in fluid flow compared to the latter relative to the control by 14.4% is observed when using additives of 0.7% (by weight of cement).

EXAMPLE 2

The dependence of the increase in concrete strength on the amount of additive is determined.

The data are shown in table 2 "Concrete compressive strength" - in power indicators (MPa) and in table 3 "Concrete strength gain relative to the control" - in relative indicators (%).

According to tables 2 and 3, graph 1 (FIG. 1) “Increase in concrete strength” and graph 2 (FIG. 2) “Increase in concrete strength”, respectively, are constructed.

From tables 2 and 3 and graphs 1, 2 it is obvious that the introduction of additives in the concrete mix can significantly increase the strength of concrete throughout the entire time of hardening, and the final strength. The maximum increase in strength is achieved with an additive concentration of 0.6% by weight of cement, calculated on the dry matter.

EXAMPLE Z.

Determine the change in concrete strength in ages with the mobility of the mixture.

The data are shown in table 4 "Dynamics of concrete strength without water withdrawal".

According to table 4, graph 3 was constructed (Fig. 3) "Strength of concrete samples without water withdrawal".

From table 4 and graph 3 it is obvious that the additive does not adversely affect concrete with a significant increase in mobility.

EXAMPLE 4

The influence of the additive on the strength characteristics of concrete and the possibility of saving cement in the mixture are determined.

The data are shown in table 5 "Dynamics of the strength of concrete with water and cement."

According to table 5 build graph 4 (figure 4) "Strength of concrete samples with water and cement."

From table 5 of graph 4 it is obvious that with an increase in the content of the additive there is a significant increase in the increase in strength. On the 7th day, with a content of 0.35% of the additive, it amounted to 22%, and with a content of 0.6% - 56%. In addition, formulations with these additives show better results than the control. So with a content of 0.35% additive and removal of 10% cement, it amounted to 3%, and with an additive content of 0.6% and removal of 20% cement - 13.4%.

Therefore, the use of additives can significantly increase the strength of concrete or, with a fixed strength, save some of the concrete.

EXAMPLE 5. Determine the effect of complex additives on the properties of concrete.

Enter D in the concrete mixture and additionally thereafter, the ferric salt (FeCl ₃ , Fe ₂ (SO ₄ ) ₃ ) is introduced in an amount of 2-4% by weight of the concrete mixture.

In the process of cement hydration, hydrolysis of iron salts proceeds according to the scheme:

1. Fe ³⁺ + H ₂ O = | Fe (OH) ²⁺ + H ⁺

2. | Fe (OH) ₂ | ⁺ + H ₂ O = | Fe (OH) ₂ | + H ⁺

3. | Fe (OH) ₂ | ⁺ + H ₂ O = Fe (OH) ₃ + 3H ⁺

or in total

Fe ³⁺ + H ₂ O = Fe (OH) ₃ + 3H ⁺

At stages 1 and 2, hydrolysis forms the base of the salt, and at the last, sparingly soluble metal hydroxides.

In an alkaline medium, Fe (OH) ₃ passes into sparingly soluble hydroferrite.

From the examples it is obvious that polymethylene polynaphthalene sulfonate Na with a degree of polycondensation equal to 2-5, in an amount of 0.3-0.7 wt.% By weight of cement, introduced into the mixture in the form of a solution, with a ratio of it and water as / 30-70 / : / 40-60 / (%), improves the physicochemical properties of concrete, increases strength throughout the hardening time, as well as the final strength, accelerates the hardening process, and sparingly soluble metal hydroxides, upon hydrolysis of the introduced salts of ferric iron, pore and condense concrete formed hydroferrite accelerates setting, improves structural characteristics.

The implementation of the claimed invention is carried out using well-known polymer compounds, technologies for their preparation and use as additives in the preparation of concrete.

The possibility of industrial application of the claimed method of concrete preparation is confirmed by the successful results of testing prototypes, and this determines, according to the applicants, its compliance with the criterion of "industrial applicability".

Using the claimed method in comparison with all known means of a similar purpose provides a significant improvement in the density and strength of concrete in the process of preparing the mixture and obtaining concrete.

Using the claimed solution provides:

- acceleration of hardening of concrete in the early stages of the process;

- increasing the strength of concrete both in the early stages of preparation and in subsequent stages after the end of the technological process;

- increasing the density of concrete.

Table 1.

LIQUID FLOW DYNAMICS

Measurable indicator Control composition
No additives Main cast The amount of additive,% 0.4 0.5 0.6 0.7 Water Consumption, l / m ³ 197 167 163 162 162

Note:

1. The control and basic compositions contain the same amount of dry components:

C = 340 kg / m ³

P = 760 kg / m ³

Щ = 1050 kg / m ³

2. The control and main structures retain the given mobility:

Cone draft OK = 15 cm

Workability grade PZ

3. In the main composition, the additive is introduced in liquid form, previously prepared.

4. The true concentration of the additive is 0.369.

5. The true content of the additive in% ratio to the mass of dry cement was 0.420, 0.512, 0.615, 0.718.

Table 2 CONCRETE STRENGTH DURING COMPRESSION.

Measurable indicator Control composition No additive Main cast
The amount of additive,% 0.4 0.5 0.6 0.7 The compressive strength, MPa by age of the samples,
day: 7 15.40 20.25 24.70 25.70 25.80 14 16.50 21,20 26.60 29.20 29.70 28 18.87 24.24 29.12 34.23 32.68 Medium strength 16.92 21.89 26.80 29.71 29.39

Table 3

CONCRETE STRENGTH GROWTH REGARDING CONTROL

Measurable indicator Main cast
The amount of additive,% 0.4 0.5 0.6 0.7 Strength gain,% by age of samples, day: 7 31.5 60,4 66.9 67.5 14 28.5 61.2 77.0 80.0 28 28.5 54.3 81.4 73,2 Average strength gain 29.5 58.6 75.1 73.6

Claims (1)

A method of modifying a concrete mixture by introducing into it an aqueous solution of polymer compounds of various molecular weights obtained by condensation of naphthalenesulfonic acid and formaldehyde, and 2-4% by weight of a mixture of ferrous or divalent iron salts, characterized in that said polymer compounds are used in an amount of 0, 3-0.7% by weight of cement at a polycondensation degree of 2-5 and at a ratio of them and water (30: 70) - (40: 60) (%), respectively, and said iron salt is introduced after said aqueous solution.

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