RU2163578C1 - Self-leveling building mixture - Google Patents

Abstract

FIELD: building materials industry, more particularly, manufacture of braces and floor coverings. SUBSTANCE: self-leveling building mixture comprises filling agent with grain size of up to 0.5 mm, filler with specific surface of 500-5000 sq. /g and magnesia cement as binder which includes component comprising active magnesium oxide, e.g. caustic magnesite or caustic dolomite, and salt component which is essentially crystallohydrate or aqueous solution of at least one salt of strong acid and two or three valent metal, e.g. magnesium chloride, ferric chloride, magnesium sulfate or mixtures thereof. Mixture comprises stabilizing additive, pigment, and modifying additives. Number of ingredients in mixture is determined from ratio between content of active magnesium oxide, salt component composition and concentration of dusty particles in filling agent. EFFECT: inexpensive mixture which is not complicated to manufacture and has optimum service and aesthetic properties. 7 cl

Description

 The invention relates to building materials, in particular to highly mobile mixtures capable of spontaneously spreading in the form of a solution on the surface and smoothing out local irregularities, and is intended primarily for the manufacture of screeds and floor coverings, and can also be used for masonry, fixing tiles making decorative coatings.

 Known self-leveling building mixture containing gypsum binder, aggregate, sulphate-yeast mash as a modifying additive and water [1].

 The disadvantages of this mixture are the high cost, poor wear resistance, swelling during hardening, the difficulty of use due to the fact that it quickly loses its mobility and self-leveling properties (in 10-15 minutes), the inability to simultaneously floor the device over a large area.

 Also known self-leveling building mixture containing Portland cement as a binder, aggregate, filler, stabilizing and modifying additives (lignosulfonates) and water [2].

 Its disadvantages are also high cost, insufficient strength, water-holding ability and wear resistance (i.e., fast abrasion) of the resulting building structures, and therefore they require additional protective coating.

 Also known self-leveling building mixture containing magnesia cement as a binder, aggregate and fiberglass [3].

 The disadvantage of this construction mixture is the narrow range of applications as a self-leveling mixture due to the presence of filler in its composition, the specific surface of which can be indefinitely large, the fast abrasion and brittleness of the products obtained, which prevents the manufacture of thin coatings, and also due to the ratio established in it ingredients that do not allow to realize the necessary mobility of the mixture and the optimal duration of the self-leveling process, and the complexity of the manufacturing process phenomena of multilayer building structures using soundproofing devices.

 The objective of the invention is to create an inexpensive and uncomplicated in the manufacture of self-leveling mortar with optimal performance and aesthetic properties, as well as expanding the arsenal of self-leveling mixtures.

 The technical result that provides the solution of this problem is to simultaneously ensure optimal mobility for the period necessary to distribute the mixture over a large area, high water-holding ability and low delamination, high adhesion to concrete, simplifying and accelerating the application process and subsequent hardening, non-shrinking, dust-free products obtained with high impact strength and abrasion, expanding the range of used starting materials with inimum or without the use of the most expensive components of the polymer.

где A - масса компонента, содержащего активный оксид магния (MgO);
C - масса солевого компонента;
n - количество составляющих (солей), входящих в состав солевого компонента;
m_i - массовая доля одной из солей в компоненте;
M_i - молекулярный вес этой соли (в безразмерных единицах), определяемый как сумма значений атомных весов элементов, входящих в химическую формулу соли, по периодической таблице элементов (таблице Менделеева);
K₁ = 200-350 (коэффициент пропорциональности);
K₂ - массовая доля активного оксида магния в компоненте, содержащем активный оксид магния,
и при следующем соотношении количества заполнителя, наполнителя и компонента, содержащего активный оксид магния:
H ≥ M₃(0,85-1,85K₃)-A, (2)
где H - масса наполнителя;
K₃ - массовая доля пылевидных частиц в заполнителе;
M₃ - масса заполнителя,
при этом содержание стабилизирующей и водоудерживающей добавки в смеси составляет 0,025-5 мас%.The essence of the invention lies in the fact that the self-leveling building mixture contains a loose aggregate, at least one stabilizing and water-retaining additive that prevents the mixture from stratifying, an inert filler with a specific surface of 500-5000 cm ² / g, as well as magnesia cement (as a binder), which includes a component containing active magnesium oxide, and a salt component, which is at least one salt of a strong acid and a metal with a valency of two to three, with the following ratio and the quantities of these components:

where A is the mass of the component containing active magnesium oxide (MgO);
C is the mass of the salt component;
n is the number of components (salts) that make up the salt component;
m _i - mass fraction of one of the salts in the component;
M _i is the molecular weight of this salt (in dimensionless units), defined as the sum of the atomic weights of the elements included in the chemical formula of the salt, according to the periodic table of elements (Mendeleev's table);
K ₁ = 200-350 (proportionality coefficient);
K ₂ - mass fraction of active magnesium oxide in a component containing active magnesium oxide,
and in the following ratio of the amount of aggregate, filler and component containing active magnesium oxide:
H ≥ M ₃ (0.85-1.85K ₃ ) -A, (2)
where H is the mass of the filler;
K ₃ - mass fraction of dusty particles in the aggregate;
M ₃ - mass of aggregate,
the content of the stabilizing and water-retaining additives in the mixture is 0.025-5 wt.%.

 The mass fraction of the substance in the component (as well as the mass fraction of dusty particles in the aggregate) shows what part is the mass of this substance from the mass of the component, if the latter is taken as a unit and is dimensionless, the mass has the corresponding dimension - ton, kilogram, etc. d.

 As a filler, the mixture may contain limestone, dolomite, quartz or granite sand or sand from slag, preferably not more than 0.5 mm.

 As a filler, the mixture may contain ground quartz and / or limestone, and as a component containing active magnesium oxide, caustic magnesite with a mass fraction of active magnesium oxide from 0.75 to 0.95.

 As a component containing active magnesium oxide, the mixture may also contain caustic dolomite with a mass fraction of active magnesium oxide from 0.15 to 0.21.

The mixture may contain a salt component in the form of a solid crystalline hydrate of at least one of the following salts of strong acids and divalent metals: magnesium chloride MgCl ₂ , ferric chloride FeCl ₃ , magnesium sulfate MgSO ₄ .

 Strong acids include acids that are completely dissociated in aqueous solutions. In this case, the component contains salts of hydrochloric and / or sulfuric acid, divalent metal of magnesium and / or ferric metal of iron as salts of strong acids.

 The mixture may contain a salt component in the form of an aqueous solution with a density of 1.1 - 1.35 kg / l of at least one of the following salts: magnesium chloride, ferric chloride, magnesium sulfate.

The mixture may additionally contain pigment in an amount of 0.5 to 3 wt.%, And as a stabilizing and water-retaining additive, at least one of the following additives: methyl cellulose, polyoxyethylene, hypane (in an amount of 0.02 - 0.5 wt.% ), bentonite clay (0.5 - 5 wt.%), sulfonated naphthalene formaldehyde resin (0.01 - 0.3 wt.%), and in addition, as modifying additives - at least one of the following additives: sodium salt sulfonated melamine-formaldehyde resin (0.1 - 1 wt.%), gypsum (0.2 - 5 wt.%), polymer dispersion (PVA) - polyvinyl etatnaya (. 3 wt%), antifoam (0.05 - 0.3 wt.%), phosphoric acid and salts thereof as well as components containing active amorphous silica (up to 3 wt% based on the active amorphous silica SiO. ₂ ).

 When these (universal for a wide range of source materials) ratios are realized, the component content ratios ensure the nature of the interaction of the salt molecules (salts), magnesium oxide and other ingredients necessary to obtain the indicated technical result, as well as the necessary concentration of dust particles in the solution with a given specific surface area.

 A filler with a specified specific surface area helps to stabilize and plasticize the ready-to-use mixture. In the case of using caustic dolomite, the amount of filler should be minimal, because dolomite contains limestone, partially replacing the filler.

 The stabilizing and water-retaining additive prevents the solution from stratifying and the loss of water from the solution into the concrete base. The stratification of the mortar mixtures made according to the present invention does not exceed 10%, and the water-holding capacity is 90-93%, which is not achieved in known mixtures. The use of sulfonated naphthalene formaldehyde resin, which, in contrast to the known mixtures, is used as a stabilizing additive, leads to a small air entrainment into the mixture, which increases the stability of the solution and reduces the shrink stress.

 The use of components containing active amorphous silica (zones of ablation of thermal power plants, ground metallurgical slag), as well as phosphoric acid and its salts provides an increase in water resistance of products from this mixture.

The use of gypsum as a modifying additive in this mixture additionally provides an increase in the ductility and impact strength of the hardened material. Both anhydrite (CaSO ₄ ) and semi-aqueous (CaSO ₄ · 0.5H ₂ O) and two-water (CaSO ₄ · 2H ₂ O) gypsum can be used.

 Pigments (ocher, red lead, chalk, azure, etc.) add decorativeness to the resulting products.

 The introduction of polymer dispersions of the PVA type serves to give the material special properties (increased adhesion to smooth surfaces, water resistance, water-repellent (hydrophobic) properties.

 The rate of mobility of the solution, estimated by the blur using a Suttard viscometer, is not lower than 23 cm.

A dry mixture containing a salt component in the form of a crystalline hydrate, for example MgCl ₂ (0-6) H ₂ O, is supplied for the production of the finished solution in packages (bags or bags) containing all the ingredients. A mixture containing a salt component in the form of an aqueous solution is supplied similarly with a separate container for this component.

 Self-leveling building mixture is prepared as follows.

Based on the set properties of the next batch of the mixture and the range of available starting materials, the value of the proportionality coefficient K _{1 is} selected and the required quantities of ingredients are determined using the indicated relations (1), (2).

If the amount of aggregate is not specified, then, as a rule, the calculation is carried out per 1000 kg of dry components of the mixture, that is:
1000 = A + H + M ₃ (3)
The calculated quantities of ingredients for the next batch of the solution are loaded into a special container with the addition of the required amount of water and mixed thoroughly until a homogeneous mass is obtained. The mass fraction of the solution of the salt component in the mixture is usually not less than 0.25, the water content is not more than 22%, pure magnesium chloride is not more than 4% (see examples).

 Dosing of the ingredients can be carried out cyclically or continuously. The dosage error should not exceed 1% for binders, water and additives, and 2% for aggregate.

 The result is a ready-to-use solution.

 4-6 point samples are taken from each batch of a solution of the same composition, which are combined into a common sample, the mass of which should be sufficient to determine the controlled parameters.

 The finished solution should be used within one hour, since in the future its mobility drops sharply.

 Testing of the sample taken should begin during the period of maintaining the normalized mobility.

 The manufacture of the floor or other structures is carried out by pouring the mortar on the surface prepared accordingly, and pouring on the open reinforcement without anti-corrosion coating is not allowed.

 Self-alignment of the mortar mixture occurs spontaneously under the influence of gravitational forces.

 In the presence of large defects (cracks, swelling, etc.), it is recommended that the solution be quickly spread over the surface of the comb squeegee, leaving insignificant, quickly leveling "scallops".

 During the first day, 30 - 50% of the structural strength is achieved, which allows you to move freely on the surface. Full normalized strength and quality indicators of the hardened solution are achieved after 28 days. Moreover, the adhesion to concrete may exceed the tensile strength of concrete.

 Example 1

 Determining the composition of a self-leveling building mixture.

To prepare the batch of the mixture take 342 kg of the salt component (C = 342), which is an aqueous solution of two metal salts (n = 2) with a density of 1.205 kg / l, with a mass fraction (content) of magnesium chloride component m ₁ = 0.15 and mass fraction of ferric chloride, component m ₂ = 0.05. The molecular weight of magnesium chloride M ₁ = 95.2, the molecular weight of ferric chloride M ₂ = 164.2.

Based on the required compressive strength of 25 MPa and a given thickness of the product (screed) of 3-10 mm, a value of K ₁ = 260 is selected.

As a component containing active magnesium oxide, caustic magnesite with a mass fraction of active magnesium oxide of K ₂ = 0.83 is used.

By substituting into the relation (1) the specified values of the calculated parameters K _1,2 , C, m _1,2 , M _1,2 (at n = 2), after performing arithmetic operations, the required mass of caustic magnesite A = 208 kg is found.

Silica sand with a grain size of up to 0.5 mm and a mass fraction of dust particles K ₃ = 0.017 is used as a filler, and silica dust with a specific surface of 2000 cm ² / g is used as a filler.

The amount of filler (in this case it is not specified) and the amount of filler are determined by jointly solving the system consisting of relations (2) and (3), as a result of which in this case there is a filler mass M ₃ = 536.8 kg, filler mass H = 247.2 kg.

 As additives, 1.49 kg of methyl cellulose, 5.96 kg of plasticizer, 1.79 kg of antifoam (fish oil) are taken.

 The mass fraction of the salt component in this embodiment of the composition of the mixture is 0.289, the water content is 21.4%, and the content of pure magnesium chloride is 4%.

 The following are examples 2, 3, 4 of the composition of the mixture, defined analogously to example 1.

 Example 2

To produce a batch of the mixture, 287.5 kg of a 15% percent solution of magnesium chloride with a density of 1.149 kg / l, 209.1 kg of caustic magnesite with a mass fraction of 0.83 magnesium oxide, 522.6 kg of silica sand with a particle size of 0.1 - 0 are taken, 5 mm, 261.3 kg of silica dust with a specific surface of 500 - 5000 cm ² / g, 1 kg of sulfonated naphthalene formaldehyde resin, 5 kg of superplasticizer (sodium salt of sulfonated melamine formaldehyde resin) and 1 kg of antifoam (fish oil). The mass fraction of the solution of the salt component is 0.287, the water content is 19%, and pure magnesium chloride is 3.3%.

 This mixture is considered basic and has a hardness of 25 MPa after 7 days from the start of solidification.

 Example 3

 To produce a batch of the mixture, 292.8 kg of a 15% percent solution of magnesium chloride, 213.0 kg of caustic magnesite with a mass fraction of 0.83 magnesium oxide, 21.3 kg of gypsum, 510.1 kg of silica sand, 239.6 kg of silica are taken dust, 1 kg of sulfonated naphthalene formaldehyde resin, 5 kg of superplasticizer (sodium salt of sulfonated melamine formaldehyde resin) and 1 kg of antifoam (fish oil). The mass fraction of the solution of the salt component is 0.293, the water content is 19%, and pure magnesium chloride is 3.4%.

 This mixture has increased elasticity and strength characteristics similar to example 1.

 Example 4

 To produce a batch of the mixture, 351.1 kg of a 15% percent solution of magnesium chloride, 780.3 kg of caustic dolomite with a mass fraction of 0.21 magnesium oxide, 200.2 kg of quartz sand (fineness up to 1.5 mm) are taken, 3.5 kg of quartz dust, 1 kg of sulfonated naphthalene-formaldehyde resin, 5 kg of superplasticizer (sodium salt of sulfonated melamine-formaldehyde resin), 1 kg of antifoam (fish oil) and 20 kg of pigment (ocher). The mass fraction of the solution of the salt component is 0.334, the water content is 22%, and pure magnesium chloride is 4%.

 This mixture is both decorative and economical, since caustic dolomite is used as a component containing active magnesium oxide, and has a hardness of 15 MPa after 7 days from the beginning of solidification.

 Only in the presence of the totality of the necessary features of the present invention, optimum mobility is ensured for the time required to distribute the solution over a large area, high water retention ability and low stratification of the mortar, high adhesion to concrete, simplification and acceleration of the process of its application and subsequent hardening , non-shrinking, dust-free products obtained with high impact strength and abrasion with a minimum content or without the use of the most expensive polymer components.

 The decrease in the cost of the latter significantly exceeds the increase in costs of the magnesian binder compared to Portland cement.

 Currently, various versions of the self-leveling building mixture have been developed and tested in practice.

 The verification results confirmed the receipt of the above technical result and the readiness of the invention for industrial production.

Sources of information
1. SU N 1231177, 1986.

 2. SU N 1470713, 1989.

 3. WO N 98/55419, 1998 (prototype).

Claims (7)

1. Self-leveling building mixture containing a loose aggregate, an inert filler with a specific surface of 500-5000 cm ² / g and at least one stabilizing and water-retaining additive that prevents delamination of the mixture, as well as magnesia cement, which includes a component containing active oxide magnesium, and a salt component, which is at least one salt of a strong acid and a metal with a valency of two to three, in the following ratio of the amount of these components

where A is the mass of the component containing active magnesium oxide;
C is the mass of the salt component;
n is the number of components (salts) that make up the salt component;
m _i - mass fraction of one of the salts in the component;
M _i is the molecular weight of this salt;
K ₁ = 200 - 350;
K ₂ - mass fraction of active magnesium oxide in a component containing active magnesium oxide,
and in the following ratio of the amount of aggregate, filler, and component containing active magnesium oxide
H ≥ M ₃ (0.85 - 1.85 K ₃ ) - A,
where H is the mass of the filler;
K ₃ - mass fraction of dusty particles in the aggregate;
M ₃ - mass of aggregate,
the content of the stabilizing and water-retaining additives in the mixture is 0.025 - 5 wt.%.  2. The mixture according to claim 1, characterized in that it contains quartz, lime, dolomite or granite sand or sand from slags with a grain size of not more than 0.5 mm as a filler.  3. A mixture according to any one of claims 1 and 2, characterized in that it contains ground quartz and / or limestone as a filler, and caustic magnesite with a mass fraction of active magnesium oxide of 0 as a component containing active magnesium oxide 75 to 0.95.  4. A mixture according to any one of claims 1 and 2, characterized in that as a component containing active magnesium oxide, it contains caustic dolomite with a mass fraction of active magnesium oxide from 0.15 to 0.21.  5. A mixture according to any one of claims 3 and 4, characterized in that it contains a salt component in the form of a solid crystalline hydrate of at least one of the following salts of magnesium chloride, ferric chloride, magnesium sulfate.  6. A mixture according to any one of claims 1 to 4, characterized in that it contains a salt component in the form of an aqueous solution with a density of 1.1 - 1.35 kg / l of at least one of the following salts: magnesium chloride, ferric chloride, sulfate magnesium.  7. A mixture according to any one of claims 1 to 6, characterized in that it further comprises a pigment in an amount of 0.5 to 3 wt.%, While it contains at least one of the following additives as a stabilizing and water-retaining additive: methyl cellulose , polyoxyethylene, hypane, bentonite clay, sulfonated naphthalene formaldehyde resin, and as modifying additives at least one of the following additives: sodium salt of sulfonated melamine formaldehyde resin, gypsum, polymer dispersion (PVA) - polyvinyl acetate, antifoam Tel, orthophosphoric acid and its salts, as well as components containing active silica.