RU2405747C1 - Polyfunctional superplasticiser for concrete mixture and mortar - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention pertains to a polyfunctional superplasticiser for concrete mixture and mortar and can be used in the industry of construction materials. The polysuperplasticiser for concrete mixture and mortar, which contains a block-copolymer of polymethylene naphthalenesulphonates (PNS) and technical lignosulphonates (TLS), a surfactant having anti-foaming action-tributylphosphate and held water, also contains a water-retaining additive - primary monoatomic aliphatic fatty acid - 2-ethylhexanol, with the following ratio of components of the superplasticiszer, wt % (in solid form - powder): PNS block copolymer and TLS 89.6-92.7, surfactant having anti-foaming action - tributylphosphate 0.3-3.0, water-retaining additive - primary monoatomic aliphatic fatty acid - 2-ethylhexanol 0.6-1.8, held water - the rest.

EFFECT: high water retention and reduced demixing of the concrete mixture and mortar with high dosage of said superplasticiser, especially heavy and cast concrete, as well as high strength of concrete and mortar during later hardening stages.

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Description

The invention relates to building materials, namely to the technology of additives of organic origin, including their complexes, used as regulators and modifiers of the properties of concrete and mortars, made on the basis of Portland cement for various purposes.

Based on the technological effects and the mechanism of action of various types of chemical additives and the real needs of the building materials industry, the most demanded are surfactants with a superplasticizing effect, among which the most widely used are superplasticizers - the polycondensation product of naphthalenesulfonic acid and formaldehyde, known as superplasticizer S-3 (Silina E. S. et al., Effect of the quality of S-3 superplasticizer on its effectiveness in concrete and mortars. M., NIIZhB Gosst oya USSR, 1985, s.84-92).

The use of S-3 superplasticizer, with all the advantages over other types of additives, in practice has also revealed certain disadvantages in that the expected technological effects in concrete did not correspond to its properties declared by various manufacturers. The reason for this is the formation of oligomers of different molecular weights during the synthesis of the additive. In addition, it turned out that cast concrete mixtures quickly lose their initial mobility, and concrete from highly mobile and cast mixtures with S-3 superplasticizer in some cases turned out to be ineffective in structures with increased frost resistance requirements. All this reduced the scope of widespread use of this plasticizer.

To improve the technological properties of mortar and concrete mixtures and increase the operational properties of mortars and concrete in accordance with the requirements of GOST 24211-03, it is necessary to use stabilizing water-retaining additives, which in optimal dosages should provide a decrease in water separation in concrete and mortar, as well as increase the resistance of mortar and concrete mixtures against delamination.

In construction, the laying and compaction of concrete should be carried out in such a way that monolithic and homogeneous concrete is ensured, projected concrete designation indicators, proper adhesion of concrete to reinforcement and embedded parts.

In domestic construction practice, in order to increase the preservation and stability of concrete mixtures during the above technological operations, the following types of special additives were proposed and tested, which in their technical effect relate to stabilizing additives that increase water retention and improve the pumpability of mixtures through a pipeline:

- polyoxyethylene (POE) - a powdered, high molecular weight surfactant of non-ionic type, not recommended for use in composition with superplasticizers, since the mixture quickly thickens;

- water-soluble methyl cellulose (MC), supplied in powder form and used only in dry building mixtures;

- a water-soluble direct emulsion of soap stock of vegetable oils in an aqueous solution of sulphide-yeast mash (complex organic additive KOD-S) ensures the shelf life of the mixture no more than 2 ... 3 hours, is difficult to compatible with the components of the naphthalene formaldehyde sulfonate type;

- regenerative effluents of sugar refining production (PC) - serial production waste containing sodium chloride, colored organic compounds and sodium hydroxide. It is not recommended for use in prestressed reinforced concrete structures, as well as in structures reinforced with high-strength reinforcing steels;

- bentonite clay (BG). Natural aluminosilicate with high ion-exchange ability and swellability. It is introduced in the form of a fine powder or aqueous suspension, it is technologically laborious to use and is applicable mainly only in low-cement concrete and mortars [Nevsky V.A. Additives in concrete and mortar. Rostov / D., 2000, p. 28-30].

These additives are usually one-component or multi-component and are not intended for joint use in cement systems containing superplasticizers such as C-3.

Further research in the field of superplasticizers led to the development of a new superplasticizer based on the products of the joint condensation of naphthalenesulfonic acid, formaldehyde and technical lignosulfonates.

Of the known technical solutions in their essence and the achieved result, the closest analogue prototype to the invention is a multifunctional superplasticizer for concrete mix and mortar according to patent RU 2342341 C2, 01/23/2007.

The specified multifunctional superplasticizer includes a block copolymer of polymethylene naphthalenesulfonates — PNS and technical lignosulfonates — TLS, a surfactant — antifoaming agents — tributyl phosphate and bound water.

Superplasticizer is developed in accordance with Technical Specifications TU 5745-333-05800142-2008, meets the requirements of GOST 24211-2003 and is entered by the State Standard of Russia in the Product Catalog under the registered name SUPRANAFT, Registration No. 049532/01.

The technological properties of this superplasticizer as a diluent and air-entraining agent are superior to the similar properties of known plasticizers, however, when using SUPRANAFT in heavy concrete technology, including cast concrete, in some cases there is water separation that exceeds the normative parameters, as well as delamination of both transported and freshly laid concrete, although the phenomenon of water separation and delamination of concrete is significantly more characteristic of other plasticizers and superplasticizers.

In this regard, it is of interest to use monatomic aliphatic alcohols in addition to superplasticizers of the naphthalene formaldehyde sulfonate type as water-holding and regulating the delamination of water-cement systems.

The patent literature [patent US 6277190 B1, 08.21.2001] describes a technical solution consisting in the use of monoatomic primary aliphatic fatty alcohols in building plasters and masonry mortars, in which cement, gypsum, lime can be used as a binder component.

These alcohols contain in the linear chain of the molecule an ethanol structure with two alkyl groups containing from six to 12 carbon atoms in each group with a total number of carbon atoms in the molecule equal to from 16 to 24, and are used only as dispersing additives in these building solutions, then as a physical and chemical basis for the use of aliphatic alcohols as water-retaining additives and delamination regulators in cement-water systems with superplasticizers like SUPRANAFT in addition to their chemical combination Property with the latter is the following.

It is known that alcohols, in particular the technically most accessible monohydric aliphatic alcohols with the number of carbon atoms in a linear chain from one to five, preventing the crystallization of calcium hydroaluminates in cement-water systems, as hydration, hydrolysis and dissolution of tricalcium aluminate (C ₃ A) increase in the liquid phase, the concentration of Al (OH) ₃ in the form of a sol. This increases the water demand of mortar and concrete mixtures up to false setting and cracking during short heat-moisture treatment (TVO), especially short (1.5-2 hours) periods of preliminary exposure before heating (at least 6 hours is required).

These disadvantages are exacerbated under additional conditions:

1) when using medium- and high-aluminate cements (with a content of C ₃ A, respectively, 5-8 and especially 9-12% of the mass of clinker);

2) with a high alkali content (R ₂ O = Na ₂ O + 0,658 K ₂ O) - more than 0.6% of the clinker mass, since in their presence in the cement-water system an alkali-containing analog C ₃ A - RC ₈ A _{3 is formed} , in which Al (OH) ₃ gel is one of the main and, at the same time, final phases arising from the hydration of highly alkaline cement; its phase transitions lead to the exfoliation of fine aggregate from the contact surface of concrete and reinforcement and the violation of their contact zone, which can lead to a dangerous drop in bearing capacity and destruction of structures and structures under normal working load in the absence of special protective measures;

3) with excessive fuel economy during clinker burning, which leads to the preservation of the intermediate (marginal) phase C ₁₂ A ₇ (mayenite) in it instead of part C ₃ A; here, Al (OH) ₃ gel is detrimental to the gel formed in the presence of RCA ₃ [Entine ZB and oth., The liquid phase alite generation model in sintering portland cement clincer. 10th International Congress on the Chemistry of Cement. Gothenburg, Sweden, June 2-6, 1997. Proceedings, ed. by H Justens, Publ. Amarkai, Gothenburg, 1997 v. 1, li046, 4 pp.].

At the same time, it is necessary to take into account that technical lignosulfonates (TLS) have an acid reaction and this accelerates the dissolution of calcium aluminates in comparison with calcium hydrosilicates during the interaction of cement with TLS and water, and, therefore, increases the risk of the above effects caused by the presence of short-chain (C ₁ -C ₄ ) monohydric aliphatic alcohols, in particular the type of ethanolamines [Tarnarutsky G.M. Development of technology and study of the construction and technical properties of hydrophobic Portland cement with multicomponent additives. Abstract of dissertation for the degree of candidate of technical sciences. M .: NIIITsement, 1974].

In this regard, the assumption was made that as water-holding additives in the composition of superplasticizers based on the products of copolymerization of GPTS and TLS, the presence of only fatty aliphatic or aromatic alcohols, as well as other alcohols, including at least one double bond C = C, is necessary for the following reasons :

firstly, they, being alkalis, although weak, reduce the harmful acid reaction of TLS; elongated linear hydrocarbon chains (C ₆ -C ₈ ) of these alcohols, due to the induction effect, locally increases this effect on functional groups;

secondly, they specifically slow down the hydration of C ₁₂ A ₇ , being adsorbed by it before hydrolysis begins, that is, before the crystal lattice breaks with water, since their molecules are surface active and are already present in the first elementary interactions of C ₁₂ A ₇ with water, and then occupy a place on the juvenile surface of C ₁₂ A ₇ hydrates, not allowing them to serve as seeds for the subsequent crystallization of hydrated neoplasms of the AFt and AFm phases; this leaves more free water in the system;

thirdly, they prevent the formation of Al (OH) ₃ sol, i.e., the adhesion of Al (OH) ₃ molecules to form a cohesive system, which reduces the water demand of the cement-water system, although they are essentially not genuine plasticizing compounds.

These positive effects of the presence of primary monohydric fatty aliphatic alcohols in cement systems explain the expected increase in the strength of cements, mortars, and concrete with the addition of such alcohols in plasticizers in the presence of TLS, alkalis, etc., since, ultimately, these additives reduce the mass fraction of non-silicate and increase the mass fraction in the cement stone of silicate hydrates, which are the main carriers of the strength of mortars and concrete. But it should be emphasized that these alcohols as water-retaining and regulating additives have not yet been used in concrete and mortar, as well as in other building mixtures based on Portland cement, together with formaldehyde sulfonate thinners of cement systems.

The objective of the invention is to increase the water-holding ability of a multifunctional superplasticizer for concrete and mortar, concrete and building mixtures and to reduce their delamination at higher dosages of the superplasticizer especially in heavy and cast concrete, as well as to increase the strength of concrete systems in the later stages of hardening.

This problem is solved by the fact that a multifunctional superplasticizer for concrete mix and mortar, including a block copolymer of polymethylene naphthalene sulfonates - PNS and technical lignosulfonates - TLS, a surfactant - antifoam surfactant - tributyl phosphate and bound water, it additionally contains a water-retaining additive aliphatic fatty alcohol - 2-ethylhexanol in the following ratio of components of superplasticizer, wt.% (in solid form - powder):

Block copolymer of PNS and technical lignosulfonates TLS 89.6-92.7 Antifoam surfactant - tributyl phosphate 0.3-3.0 Water Retainer - Primary Monatomic aliphatic fatty alcohol - 2-ethylhexanol 0.6-1.8 Water bound rest

The invention consists in the following.

Monoatomic aliphatic fatty alcohols with linear hydrocarbon chains having short side methyl groups in the complex superplasticizer, chemically integral with it, activate through the common molecular system and the corresponding donor – acceptor bonds in the • hydroxyl groups the monomolecular aqueous layer surrounding their hydrocarbon chains. Functional groups in alcohols generate activated hydrated electrons in this layer, delocalized over the entire area of the contact water layer. As a result, a high-temperature (corresponding to 293 ± 20 K) superconductivity is attached to this layer, accompanied by a significant decrease in the viscosity of water [A. Stekhin. et al. Structured water: nonlinear effects. M .: Publishing. LCI, 2008, p.139, 175, 251, etc.]. This ensures an increase in the water-reducing action of the additive, especially taking into account linear long-chain alcohol molecules, which significantly increase the area of the superconducting contact layer around the additive molecules and, accordingly, additionally reduce the total water content of cement-water systems - mortar and concrete.

At the same time, there is a significant decrease in water separation - the main disadvantage of the known superplasticizers based on naphthalene sulfonates, which is especially characteristic for concrete with the introduction of superplasticizers in the concrete mix. Accordingly, the addition of 2-ethylhexanol has the maximum positive effect on the behavior of concrete mixtures and concretes based on them, manifested in an increase in strength in the early and subsequent hardening periods due to a decrease in W / C, which corresponds to the manifestation of superposition and synergistic effects, in which the mutual effects of the components are superimposed superplasticizer, and the overall effect significantly exceeds the total and similar contribution of each of the components.

The optimal ratio of components in a multifunctional plasticizer was found experimentally.

For the preparation of multifunctional superplasticizer

The following components were used:

SUPRANAFT superplasticizer according to TU 5745-333-05800142-2008

Surfactant - antifoam tributyl phosphate according to TU 6-02-733-84

Water-holding additive - 2-ethylhexonal GOST 26624-85

Example

To study the properties of the experimental sample of the superplasticizer of the present invention, a concrete mixture was prepared containing medium-aluminate cement M 500 with NG = 26.5%; silica sand with a particle size modulus of 2.30; granite crushed stone, consisting of 40% of grains of a fraction of 5-10 mm and 60% of grains of a fraction of 10-20 mm. The composition of concrete is Ts: P: Sh: V = 1: 2,34: 2,94: 1,94. Superplasticizer was administered with all mixing water. The mixture was prepared in a forced action mixer. The workability of the concrete mixture and the determination of the delamination of the concrete mixture was determined according to GOST 10181.4-81 “Concrete mixtures. Methods for determining delamination. "

Concrete samples were prepared from concrete mix for strength tests, solidified under normal heat and humidity conditions. The strength of the samples was determined in accordance with GOST R 53231-2008 “Concretes. Strength Control Rules. ” Concrete mixtures containing a superplasticizer to the claimed component ratios were tested. We also tested concrete samples made in accordance with the composition specified in the well-known technical solution (prototype analogue), as well as concrete samples containing 2.5% superplasticizer, solidified under normal heat and humidity conditions.

The composition of superplasticizers according to the well-known technical solution and the present invention, as well as the construction and technical characteristics of concrete samples are presented in tables 1 and 2, respectively.

Table 1 The composition of the multifunctional superplasticizer SUPRANAFT, wt.% Example, Experience No. Super plasticizer block copolymer Surfactant tributyl phosphate 2-ethylhexanol 1 control - - 2 89.6 0.3 0.6 3 91.2 1,2 1,2 four 92.7 3.0 1.8

table 2 Construction and technical characteristics of concrete samples Example, Experience No. Consumption of superplasticizer,% by weight of cement OK, cm (H / D = 0.51) Compressive Strength, MPa (28 days) Water separation, P _in ,% Delamination, P _p % 1 control 0.7 25 42.3 0.70 3,5 2 0.7 25 42.1 0.40 2,8 3 0.7 24 43,2 0.21 1,1 four 0.7 25 43.8 0.25 1,6

To determine the effect of a multifunctional superplasticizer on the strength characteristics of concrete, as well as water separation and delamination, samples were prepared from a mixture (OK = 4-5.5) equally moving with an additional (control) mixture. The test results of concrete samples are shown in table 2, from which it can be seen that the proposed multifunctional superplasticizer with the addition of 2-ethylhexanol confirm the increase in strength, decrease in water separation and delamination of concrete.

Thus, the proposed composition of the components makes it possible to obtain a multifunctional superplasticizer, highly effective and new for the technology of concrete systems and mortars.

Claims (1)

A multifunctional superplasticizer for concrete mix and mortar, including a block copolymer of polymethylene naphthalene sulfonates PNS and technical lignosulfonates TLS, an antifoam surfactant - tributyl phosphate and bound water, characterized in that it additionally contains a water-retaining adipate - primary fatty one ethylhexanol in the following ratio of components of superplasticizer, wt.% (in solid form - powder):
Block copolymer PNS and technical lignosulfonates TLS 89.6-92.7 Antifoam surfactant - tributyl phosphate 0.3-3.0 Water Retainer - Primary Monatomic aliphatic fatty alcohol - 2-ethylhexanol 0.6-1.8 Water bound Rest