RU2527436C2 - Complex additive for cement systems (versions) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to field of construction materials, in particular to compositions of complex additive, applied in production of concretes, mortars, concrete and reinforced concrete products. Complex additive for cement systems, containing superplasticiser, and mixture of electrolytes, additionally contains organic viscosity regulator; as viscosity regulator used are non-ionogenic and ionogenic cellulose ethers, modified starches, polysaccharides of vegetable or microbiological origin, binary mixtures of monomer cationic and anionic surface-active substances or mixture of several said components with the following content of said components, wt %: superplasticiser 51-84, mixture of electrolytes 15-45, organic viscosity regulator 1-4. In accordance with another version complex additive for cement systems, contains, wt %: superplasticiser 1-10, mixture of electrolytes 1.5-4.5, organic viscosity regulator 0.05-0.5, water-retaining component 85.45-97.45, as water-retaining component it contains mixture of several finely milled natural minerals from the group: limestone, dolomite, sand and/or mixture of several technogenic finely disperse materials of the group, including fly ash, blast furnace slag, microsilica, metakaolin.

EFFECT: reduction of values of apparent viscosity to minimal ones with preservation of threshold values of shear stress.

3 cl, 1 dwg, 2 tbl, 18 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, mortar, concrete and reinforced concrete products.

Cement systems are viscoplastic systems and their rheological properties in accordance with the Bingham model can be described by the following characteristics: ultimate shear stress and viscosity. If the viscosity of classical liquids is constant and does not depend on the value of applied external forces, then the viscosity of cement systems even at a constant temperature varies several times depending on the magnitude of external forces acting on the system. Viscosity depends on the shear stress of the system or the rate of shear strain.

At low shear stresses, the intact initial structure of the cement system is preserved, which is characterized by high viscosity and some stiffness, i.e. ability to withstand external forces, including gravity. After reaching the ultimate stress corresponding to the cohesion forces, the destruction of the internal structure begins, which can continue until its complete destruction. With the destruction of the internal structure with an increase in shear stresses, the effective viscosity of cement systems constantly decreases [Yu. M. Bazhenov Concrete technology.-M.: Publishing house ASV, 2002].

Superplasticizers can have a similar effect on cement systems: they reduce the ultimate shear stress and plastic viscosity, and at high dosages of superplasticizers, the values of the ultimate shear stress can decrease to almost zero.

Such plasticized cement systems have high mobility (fluidity), but are prone to segregation processes: i.e. are unstable in relation to water and solution separation. To increase the connectivity of plasticized cement systems, thixotropy, i.e. maintaining integrity in the absence of external influences and high mobility when exposed to minimal external forces.

Thus, when using superplasticizers, an important element in the preparation of non-stratified highly mobile cement systems is the provision of an optimal value of shear stress with a minimum apparent viscosity.

A well-known complex additive in concrete mixtures containing a mixture of salts based on sodium thiosulfate and rhodanide, amkyrosis and C-3 superplasticizer in the following ratio, wt.%: A mixture of salts based on thiosulfate and sodium rhodanide - 50-98, amkyrosis - 1-40, S-3 superplasticizer - the rest [Kovalenko SV, Bespalov AI, Kovalenko VV, Bespalov AA Complex additive in concrete mixes and mortars. RF patent 2310618, publ. 2007.11.20.].

The disadvantage of this complex additive is the high content in its composition (more than half) of a mixture of salts based on sodium thiosulfate and thiocyanate, as a result of which the additive in the range of permissible dosages (up to 1%) is characterized by an insufficiently high plasticizing ability, and cement systems with it have relatively high values viscosity and ultimate shear stress.

The closest in technical essence and the achieved technical result to the proposed additive according to option 1 is a complex additive in concrete mixes and mortars [RF Patent 2228306 "Complex additive in concrete mixes and mortars"], containing a mixture of ballast salts of coke oven gas desulfurization based on thiosulfate and sodium thiocyanate and an organic component; as an organic component, the additive contains C-3 superplasticizer in the following ratio, wt.%: a mixture of ballast salts of coke oven desulfurization based on thiosulfate and sodium thiocyanate 61-95, C-3 superplasticizer - the rest.

However, the disadvantage of this additive is that low viscosity cement systems are achieved at relatively high dosages and that the additive does not provide control of the rheological characteristics of cement systems.

The closest analogue to the proposed additive according to option 2 is the additive [Patent RU 2006141696 "Systems based on cement, which use water-retaining substances obtained from unbleached cotton lint"]. The specified composition of the mixture for use in dry cement-based mortars includes cellulose ether in an amount of from 20 to 99.9 wt.%, Selected from the group consisting of alkyl hydroxyalkyl cellulose, hydroxyalkyl cellulose and mixtures thereof, obtained from unbleached cotton lint, and at least one additive in an amount of from 0.1 to 80 wt.%, selected from the group including organic and inorganic thickening agents, anti-sagging agents, additives involving air, wetting agents, foam carriers, superplasticizers, dispersants, calcium-forming complexes, retarders, accelerators, re-dispersible water-repellents, powders, biopolymers and fibers, where, when this composition is used in a masonry-based mortar composition and mixed with sufficient water, this composition forms a mortar for masonry or a finely divided joint mortar.

Moreover, the content of one or more additives including a mixture of superplasticizer and accelerator can be from 0.001 to 20 wt.%, And the content of finely dispersed material (water-retaining component) can be from 10 to 95 wt.%; cellulose ether - viscosity regulator from 0.001 to 1.0 wt.%).

The disadvantage of the additive is the inability to maintain threshold values of shear stress when reduced to the minimum values of apparent viscosity.

The technical task of the invention of the complex additive according to option 1 is the creation of a complex additive that directionally regulates the rheological characteristics of cement systems, namely, reduces the apparent viscosity to minimum values while maintaining the threshold values of shear stress.

An object of the invention of the complex additive according to option 2 is the creation of a complex additive that directionally regulates the rheological characteristics of cement systems, namely, reduces the apparent viscosity to minimum values while maintaining threshold values of shear stress.

The tasks are solved in that:

the complex additive for cement systems according to option 1 contains a superplasticizer, a mixture of electrolytes and an organic viscosity regulator in the following ratio, wt.%:

superplasticizer 51-84 electrolyte mixture 15-45 organic viscosity regulator 1-4

The polycondensation product of naphthalene sulfonic acid and formaldehyde, the copolycondensation products of naphthalene sulfonic acid, sulfomethylated melamine-formaldehyde resins, modified sulfomethylated melamine-formaldehyde resins, lignosulfonates, modified lignosulfonates, polycarboxylates are used as superplasticizers.

As a mixture of electrolytes, a mixture of alkali metal sulfates with nitrates of alkali or alkaline earth metals, technical thiosulfate and sodium thiocyanate, formates of alkali or alkaline earth metals or a mixture of several of these components is used.

Non-ionic and ionic cellulose ethers, modified starches, plant or microbiological polysaccharides, binary mixtures of monomeric cationic and anionic surfactants, or a mixture of several of these components are used as an organic viscosity regulator.

The complex additive for cement systems of the present invention according to option 2 contains a superplasticizer, a mixture of electrolytes, an organic viscosity regulator and a water-retaining component, while a mixture of several finely ground natural minerals selected from the group consisting of limestone, dolomite, sand and / or a mixture of several technogenic fine materials that are selected from the group comprising fly ash, blast furnace slag, silica fume, metakaolin in the following ratio, wt.%:

superplasticizer 1-10 electrolyte mixture 1,5-4,5 organic viscosity regulator 0.05-0.5 water retention component 85.45-97.45

The polycondensation product of naphthalene sulfonic acid and formaldehyde, the copolycondensation products of naphthalene sulfonic acid, sulfomethylated melamine-formaldehyde resins, modified sulfomethylated melamine-formaldehyde resins, lignosulfonates, modified lignosulfonates, polycarboxylates are used as superplasticizers.

As a mixture of electrolytes, a mixture of alkali metal sulfates with nitrates of alkali or alkaline earth metals, technical thiosulfate and sodium thiocyanate, formates of alkali or alkaline earth metals or a mixture of several of these components is used.

Non-ionic and ionic cellulose ethers, modified starches, plant or microbiological polysaccharides, binary mixtures of monomeric cationic and anionic surfactants, or a mixture of several of these components are used as an organic viscosity regulator.

The use of a complex additive according to this application in a variant with a water-retaining component allows to obtain self-compacting concrete (concrete that can spread under its own weight, completely fill the form and provide encapsulation of reinforcing bars without reducing the bonding characteristics of the mixture).

Between the totality of the essential features of the claimed group of inventions and the achieved technical result, there is a causal relationship.

The creation of the internal structure of cement systems depends on many factors, including the value of the W / C ratio, the dispersion of Portland cement, and the activity of clinker minerals. An important role in ensuring the connectivity of the system belongs to the primary hydration products, especially CSH and CASH gels, which have a highly developed hydrophilic surface and are capable of retaining significant amounts of water.

Superplasticizer, when introduced into cement systems, affects not only rheological characteristics, but is also able to slow down the reactions of clinker minerals; this effect is especially evident at high dosages of superplasticizer or when using additives with a delay effect (lignosulfonates and polycarboxylates with a certain structure).

To control the rate of initial hydration reactions, the number of highly dispersed neoplasms and, therefore, the connectivity of the system, the content of superplasticizer should be compensated by the introduction of electrolytes that accelerate the dissolution and hydration of anhydrous clinker minerals.

The introduction of an organic viscosity regulator allows for constant values of the apparent viscosity of the system to increase the ultimate shear stress [M. Collepardi. Admixtures-Enhancing concrete performance // 6th International Congress, Global Construction, Ultimate Concrete Opportunities, Dundee, U.K. - 5-7 July 2005] and, accordingly, the connectivity of the system.

Introduction to the composition of the additive a water-retaining component, which is used as a mixture of several finely ground natural minerals, which are selected from the group comprising limestone, dolomite, sand and / or a mixture of several technogenic finely dispersed materials, which are selected from the group comprising fly ash, blast furnace slag, silica fume, metakaolin allows the production of self-compacting concrete mixtures with high resistance to delamination even when concreting densely reinforced structures, regardless of the type used cement and grades on the cone blur (P1-P6).

The inventive range of ratios of the components of complex additives according to options 1 and 2 is established experimentally and is optimal. In the complex additive according to option 1, when the content of superplasticizer is above 84%, the proportion of electrolytes becomes too small to compensate for the effect of slowing down hydration, concrete and mortar mixes are obtained with high fluidity but low thixotropy, i.e. prone to delamination. When the content of superplasticizer is lower than 51%, the necessary initial grade for the mobility of the concrete mixture P5 is not provided.

In more detail, the technical nature of the invention and the effects achieved can be illustrated by the following examples.

Example 1 additive prototype (for a complex additive for cement systems according to option 1): superplasticizer C-3 - 39, a mixture of electrolytes based on thiosulfate and sodium thiocyanate - 61.

Example 2 - additive prototype for a complex additive for cement systems according to option 2: superplasticizer - C-3 (Na salt of the polycondensation product of β-naphthalene sulfonic acid and formaldehyde) - 10; a mixture of electrolytes - sodium sulfate and a mixture of technical thiosulfate and sodium thiocyanate - 10: an organic viscosity regulator - methyl cellulose obtained from unbleached cotton lint - 1; water-retaining component - ground limestone - 79.

Examples 3-18 of the additives of the invention.

Example 3: Na-salt of the polycondensation product of β-naphthalene sulfonic acid and formaldehyde - 51, a mixture of electrolytes (sodium sulfate and a mixture of technical thiosulfate and sodium thiocyanate) - 45, an organic viscosity regulator (guar - vegetable polysaccharide) - 4;

example 4: sulfomethylated melamine formaldehyde resin - 61; a mixture of electrolytes (sulfate and sodium formate 10:90) - 36; ionic cellulose ether (CMC) - 3;

Example 5: modified sulfomethylated melamine-formaldehyde resin (MFAR) - 72, a mixture of electrolytes (sulphate and sodium nitrate 20:80) - 26, non-ionic cellulose ether - 2;

Example 6: Superplasticizer "Polyplast SP-4" (copolycondensation product based on naphthalenesulfonic acids) - 84, a mixture of electrolytes (potassium sulfate and magnesium nitrate 70:30) - 15, ionic cellulose ether - 1;

example 7: lignosulfonates - 75; a mixture of electrolytes (sulfate and sodium thiocyanate 50:50) - 23, a mixture of nonionic and ionic cellulose ethers - 2;

example 8: modified lignosulfonates - 52; a mixture of electrolytes (sodium sulfate and thiosulfate 40:60) - 45, a mixture of CMC and modified starch - 3;

Example 9: a mixture of polycarboxylates and lignosulfonates - 80; a mixture of electrolytes (sulfate and sodium nitrate 10:90) - 16, a binary mixture of monomeric cationic and anionic surfactants - 4;

Example 10: polycarboxylates - 55, a mixture of electrolytes (sulfate, thiosulfate and sodium thiocyanate 25:35:40) - 43, modified starch + nonionic cellulose ether - 2;

Example 11: Na-salt of the polycondensation product of β-naphthalenesulfonic acid and formaldehyde + LST - 70; a mixture of electrolytes (sulfate, thiosulfate and sodium formate 30:50:20) - 28; CMC + diutan (polysaccharide of microbiological origin) - 2;

Example 12: Na-salt of the polycondensation product of β-naphthalene sulfonic acid and formaldehyde - 1, a mixture of electrolytes (sodium sulfate and a mixture of technical thiosulfate and sodium thiocyanate) - 1.5, an organic viscosity regulator (guar - vegetable polysaccharide) - 0.05; water-retaining component (a mixture of limestone and dolomite 50:50) - 97.45;

Example 13: sulfomethylated melamine formaldehyde resin - 10; a mixture of electrolytes (sulfate and sodium formate 10:90) - 3; ionic cellulose ether (CMC) - 0.5; water-retaining component (a mixture of limestone, dolomite and sand 25:35:40) - 86.5;

Example 14: modified sulfomethylated melamine formaldehyde resin (MFAR) - 6, a mixture of electrolytes (sulfate and sodium nitrate 20:80) - 4.5, non-ionic cellulose ether - 0.5; water-retaining component (a mixture of fly ash and blast furnace slag 45:55) - 85.45;

Example 15: Superplasticizer "Polyplast SP-4" (copolycondensation product based on naphthalenesulfonic acids) - 5, a mixture of electrolytes (potassium sulfate and magnesium nitrate 70:30) - 2, ionic cellulose ether - 0.25; water-retaining component (mixture of metakaolin and fly ash 35:65) - 92.75;

example 16: lignosulfonates - 10; a mixture of electrolytes (sodium sulfate and thiocyanate 50:50) - 2.5, a mixture of nonionic and ionic cellulose ethers - 0.3; water-retaining component (a mixture of fly ash, silica fume, metakaolin 33.3: 33.3: 33.4) - 87.2;

example 17: modified lignosulfonates - 7; a mixture of electrolytes (sodium sulfate and sodium thiosulfate 40:60) - 1.5, a mixture of CMC and modified starch - 0.45; water-retaining component (a mixture of sand, limestone, silica fume, blast furnace slag 25: 25: 25: 25) - 91.05.

Example 18: a mixture of polycarboxylates and lignosulfonates - 4; a mixture of electrolytes (sulfate and sodium nitrate 10:90) - 3.5, a binary mixture of monomeric cationic and anionic surfactants - 0.15; water-retaining component (a mixture of dolomite and blast furnace slag 45:55) - 92.35.

The results of comparative tests of additives of the prototypes and according to this application for option 1 are shown in table 1. The properties of the complex additives of the present invention were checked in accordance with GOST 30459-2003 on a concrete mixture of the composition (kg / m ³ ): cement - 350, sand - 850, crushed stone - 990, water - 185. The additive was dosed by dry substance in% of mass of cement. Mobility was determined in accordance with GOST 10181.1, strength in accordance with GOST 10180. Analyzing the table, we can conclude that maintaining additives in the concrete mix according to this application allows to obtain highly mobile concrete mixes that are not inferior in plasticization and strength characteristics to the prototype additive.

Table 2 presents the tests of additives according to this application (option 2) and additive prototype in the composition of self-compacting concrete. Additives were used in the indicated ratio in a dosage of 20% by weight of cement on a dry matter basis. As can be seen, the spread (filling capacity) and water separation (segregation resistance) of self-compacting concrete with an additive according to this application exceed these characteristics for concrete with an additive prototype.

Graph 1 illustrates the change in the apparent viscosity of self-compacting concrete with an additive according to this application (option 1) for different values of the spread. The viscosity and ultimate shear stress of the concrete mixture was determined using a Veitelson viscometer. The spread of the concrete mixture with additives of the compositions of examples 12-18 according to table 2 was regulated by changing the water-cement ratio. With a constant value of apparent viscosity, the ultimate shear stress for concrete with additives according to the application is 10-20 Pa higher than the maximum shear stress of concrete with an additive prototype (i.e., a distinct thixotropic effect is observed).

Table 1  The influence of the ratio of the components of the additives on the consumer properties of concrete mix and concrete (option 1) The ratio of the components of the complex additives, wt.% Dosage% Draft
cone, cm The viscosity of the concrete mixture, Pa * s Ultimate shear stress, Pa Compressive strength, MPa, aged superplasticizer electrolyte mixture organic viscosity regulator 1 day 7 days 28 days Example 1 39 61 - 0.8 17 51 430 9.3 28,4 32.1 example 3 51 45 four 0.8 twenty 25 130 10.9 29.0 33.9 example 4 61 36 3 0.8 21 22 110 10.6 29.0 34.0 example 5 72 26 2 0.8 22 eighteen 80 9.9 28,4 33.5 example 6 84 fifteen one 0.8 23 fifteen 60 9.2 28.0 32,0 example 7 75 23 2 0.8 22 17 78 9D 28.0 33,4 example 8 52 45 3 0.8 twenty 19 93 9.7 28.6 34.0 example 9 80 16 four 0.8 22 twenty 87 10.0 28.9 32.9 example 10 55 43 2 0.8 21 21 90 10.9 29.1 33.7 example 11 70 28 2 0.8 21 23 one hundred 10.5 28.9 33.1

table 2  The influence of the ratio of the components of the additives on the rheological properties of self-compacting concrete mixtures (option 2) The ratio of the components of the complex additives, wt.% Water separation,% Cone draft, cm Blur, cm Compression strength at the age of 28 days, MPa Note superplasticizer electrolyte mixture organic viscosity regulator water retention component Example 2 10 10 one 79 2.2 22 56 38,2 prototype Example 12 one 1,5 0.05 97.45 0.1 26 61 42.3 Example 13 10 3 0.5 86.5 0.3 27 70 44.3 Example 14 6 4,5 0.5 85.45 0.3 27 69 43,2 Example 15 5 2 0.25 92.75 0.2 26 68 42.0 Example 16 10 2,5 0.3 87.2 0.3 27 70 43 Example 17 7 1,5 0.45 91.05 0.2 26 69 44.1 Example 18 four 3,5 0.15 92.35 0.1 26 68 42.0

Literature

1. Bazhenov Yu.M. Concrete technology.-M.: DIA Publishing House, 2002.

2. Kovalenko SV, Bespalov AI, Kovalenko VV, Bespalov AA Complex additive in concrete mixes and mortars. RF patent 2310618, publ. 2007.11.20.

3. Likhopud A.P., Sinaiko N.P., Bashlykov N.F., Mayorova I.I. Complex additive in concrete mixes and mortars. Patent RU 2228306, publ. 2004.05.10.

4. M. Collepardi. Admixtures-Enhancing concrete performance // 6th International Congress, Global Construction, Ultimate Concrete Opportunities, Dundee, U.K. - 5-7 July 2005

Claims (3)

1. A complex additive for cement systems containing a superplasticizer, a mixture of electrolytes, characterized in that it is additionally introduced an organic viscosity regulator, while nonionic and ionic cellulose ethers, modified starches, plant or microbiological polysaccharides, binary are used as an organic viscosity regulator mixtures of monomeric cationic and anionic surfactants or a mixture of several of these components in the following contents components, wt.%:
superplasticizer 51-84 electrolyte mixture 15-45 organic viscosity regulator 1-4 2. The complex additive for cement systems according to claim 1, characterized in that the polycondensation product of β-naphthalene sulfonic acid and formaldehyde, the copolycondensation product of naphthalene sulfonic acids, sulfomethylated melamine-formaldehyde resins, modified sulfomethylated melamine-formaldehyde resins, lignonated sulfonylated lignosulfonate, specified products. 3. A complex additive for cement systems containing a superplasticizer, a mixture of electrolytes, an organic viscosity regulator, a water-retaining component, characterized in that as a water-retaining component a mixture of several finely ground natural minerals is used, which are selected from the group comprising limestone, dolomite, sand and / or a mixture of several technogenic fine materials, which are selected from the group comprising fly ash, blast furnace slag, silica fume, metakaolin in the following ratio, wt.%:
superplasticizer 1-10 electrolyte mixture 1,5-4,5 organic viscosity regulator 0.05-0.5 water retention component 85.45-97.45

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