RU2453516C1 - Self-levelling magnesia composition - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: self-levelling magnesia composition, containing a magnesia cement, including active magnesium oxide and a salt component in the form of an aqueous solution of magnesium chloride, an inert filler - a quartz or granite sand, a stabilising and a water-retaining additive, and also a complex modifying additive, the active magnesium oxide is caustic brusite, and the stabilising and water-retaining additive is higher alcohol of the row C₁₂-C₁₈. At the same time the modifying complex additive consists of a hydrophobic surfactant in the form of a copolymer of vinyl chloride\ethylene\ vinyl laurate or vinyl acetate \versatate\ acrylate, or vinyl acetate\ vinyl alcohol and hydroxycarboxylic acid at the following ratio of components, wt %; caustic brucite 21.0-31.5, filler - quartz or granite sand 31.5-53.2, stabilising and water-retaining additive - alcohol of the row C₁₂-C₁₈ 0.5-1.8, complex modifying additive: the specified hydrophobic surfactant of copolymer 0.5-1.0, hydroxycaroxylic acid 0.2-1.5, salt component - aqueous solution of the magnesium oxide - balance.

EFFECT: increased time of composition viability, higher strength in compression, improved decorative properties of the composition, expansion of raw base of the magnesium cement and assortment of materials on its basis.

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Description

The invention relates to the building materials industry and can be used to obtain cast decorative products, monolithic structures such as bulk floors, when plugging cracks in collapsing buildings, as well as in the production of dry mixes for decorative and artistic decoration of buildings and structures.

Known raw material mixture, including, wt.%: Caustic magnesite - 15-21.5, ground main granular slag - 24.0-28.5, ground blast furnace dust or sludge gas treatment - 9.0-30.0, solution bischofite with a density of 1.3 g / cm ³ - 9.30-11.16, aluminosilicate additive (waste from mechanical cutting of decorative sections on the surface of crystal products) - 1.0-5.0, water (including chemically bonded bischofite) - the rest. This raw mix in the closed state has high mobility and viability, and upon curing it forms a material with a sufficiently high water resistance and compressive strength [1].

The disadvantages of the raw mix include:

- a very long pot life in a highly mobile state of the mixture and a slow set of strength (time before setting at 20 ° C is from 21 to 28 hours), which limits the possibility of using the mixture for the manufacture of bulk floors, coatings, screeds, etc., the mixture additionally requires long-term monitoring and care before commissioning;

- the presence in the mixture of slag and blast furnace dust or sludge from blast furnaces increases the compressive strength of the composition, but at the same time gives it brittleness and a tendency to crack formation. The invention does not have complete data on the mechanical properties, in particular, on bending and tensile strengths; there is no data on crack resistance;

- there is no data on the water absorption of the composition;

- the presence in the mixture of slag, blast furnace dust or slag from blast furnaces gives the composition an unaesthetic appearance.

Known raw material composition for the manufacture of building materials and products, including magnesia binder, which includes caustic magnesite and an aqueous solution of magnesium chloride with a density of 1.19-1.3 kg / l, mineral filler and additives, while the mixture is taken as a mineral filler solids having a specific surface 3000-6500 cm ² / g consisting of fly ash from thermal power plants, quartz sand, kaolin and a hydrophobic surfactant - surfactant copolymer powder: vinyl acetate / vinyl alcohol or vinilhlori a / ethylene, or vinyl chloride / ethylene / vinyl laurate, and additionally contains a water-reducing additive - water-soluble cellulose ether in the following ratio of components, wt.%: caustic magnesite - 28.0-40.0, quartz sand - 30.0-42.0 , fly ash of thermal power plants - 10.0-14.0, kaolin - 1.0-4.0, the specified surfactant - 0.5-0.9, water-reducing additive - 0.01-0.30, water-soluble cellulose ether - 0 , 01-0,02, and the rest is a solution of magnesium chloride [2].

This raw material composition during mixing forms a highly mobile mass with a pot life sufficient to distribute the mixture over a large surface in the manufacture of bulk floors. Materials and products based on this raw material composition have a fairly high mechanical strength and low water absorption.

The disadvantages of the invention are:

- the complex composition, including 8-9 ingredients, including highly dispersed substances with a specific surface of 3000-6500 cm ² / g;

- as the mineral filler of the composition is used fly ash TPP, giving the material brittleness and a tendency to crack formation;

- the use as a filler of the composition of industrial wastes such as fly ash or blast furnace dust does not allow to obtain materials and products of high aesthetic quality, especially colored with one or another delicate floral shade. In addition, fly ash is characterized by inconsistent composition, which requires additional control and adjustment of the composition of the raw material composition.

Known self-leveling magnesia mixture containing magnesia cement, consisting of active magnesium oxide and a salt component in the form of an aqueous solution of magnesium chloride, an inert filler, for example, silica sand, a stabilizing and water-retaining additive, as well as a complex modifying additive [3].

This mixture during mixing has high mobility, uniformity and the ability to self-level under the influence of gravitational forces, which makes it possible to use it to obtain molded building products and structures. This invention is the closest in technical essence and we have chosen as a prototype.

However, this self-leveling building mixture has significant disadvantages:

- a relatively short pot life of the mixture in a highly mobile state (1 hour);

- the mechanical strength of the mixture is 25 MPa in compression, there are no data on the strength during bending and tension;

- the known composition of the mixture cannot be classified as inexpensive and economical, since they use highly dispersed substances such as ground quartz (filler), dusty quartz with a given specific surface (for stabilization and plasticization of the mass), fish oil as an antifoam agent;

- the use of blast furnace slag as a filler gives the composition brittleness and greatly affects the aesthetic properties;

- the use of caustic magnesite and caustic dolomite as active magnesium oxide, originally colored with impurities (most often Pe ₂ O ₃ and other oxides of transition group elements), makes it impossible to give the composition bright colors.

The objective of the invention is to increase the range of time the pot life of a composition while increasing its mechanical strength and decorative qualities, as well as reducing the cost of a self-leveling composition, expanding the raw material base of magnesia cement and the range of materials based on it.

This is achieved by the fact that in a self-leveling magnesia composition containing magnesia cement, consisting of active magnesium oxide and a salt component in the form of an aqueous solution of magnesium chloride, an inert filler, for example, silica sand, a stabilizing and water-retaining additive, as well as a complex modifying additive, magnesian cement as active magnesium oxide, brucite contains caustic, and as a stabilizing and water-retaining additive taken higher alcohol series of C ₁₂ -C _18, wherein the modifying schaya complex additive consists of hydrophobic surfactant in the form of a copolymer of vinyl chloride / ethylene / vinyl laurate or vinyl acetate / versatate / acrylate or vinyl acetate / vinyl alcohol and a hydroxycarboxylic acid at the following component ratio, wt.%:

caustic brucite 21.0-31.5 filler - quartz or granite sand 31.5-53.2 stabilizing and water-retaining alcohol additive C ₁₂ -C ₁₈ 0.5-1.8 complex modifying additive: specified hydrophobic surfactant copolymer 0.5-1.0 hydroxycarboxylic acid 0.2-1.5 salt component - aqueous solution magnesium chloride rest

The following raw materials were used to obtain a self-leveling magnesia composition.

The composition and some physico-chemical parameters of caustic brucite are given below:

Content, wt.%

(on absolutely dry substance):

- magnesium oxide (MgO), not less 80 - calcium oxide (CaO) 4-5 - silicon oxide (SiO ₂ ) 5-6 - iron oxide (Fe ₂ O ₃ ) 0.05 mass fraction of moisture (%), no more 0.5 the residue on a sieve No. 01 (100 μm),% 1,5 product appearance white

To obtain compositions with high decorative qualities, silica sand washed and cleaned of iron oxides with a grain size of not more than 0.6 mm was used as a filler. For compositions for construction purposes that do not require high aesthetic characteristics, both quartz sands and granite sands painted with impurities can be used as filler.

The mixing of the raw material was carried out on the salt component in the form of an aqueous solution of magnesium chloride (technical crystalline MgCl ₂ · 6H ₂ O, GOST 7759-73) with a density of 1.1-13 kg / l. As a stabilizing and water-retaining additive that prevents separation of the sealed mass, higher alcohol of the C ₁₂ -C ₁₈ series, forming an azeotropic mixture with water, was used.

The complex modifying additive contains two substances:

hydroxycarboxylic acid and hydrophobic surfactants in the form of interchangeable copolymers: vinyl acetate / vinyl alcohol or vinyl acetate / versatate / acrylate or vinyl chloride / ethylene / vinyl laurate. Active hydroxycarboxylic acid in the form of a water-soluble powder with a grain size of up to 0.5 mm played the role of a retarder for the "setting" of the closed mass in both the initial and final stages, and also affected its mobility in the viscous-flowing state, and the hydrophobic copolymer provided a low amount of water absorption composition.

Self-leveling magnesia composition is made as follows.

Dosed quantities of caustic brucite, quartz sand and additives are mixed dry for 3-5 minutes, then the resulting mixture is closed with an aqueous solution of magnesium chloride with a density of 1.1-1.3 kg / l, followed by stirring in a paddle mixer to a viscous flowing state, after which determines the spread (by Suttord viscometer) in centimeters and the viability of the mass in a mobile state before setting (in hours). Two types of samples are cast from the prepared highly mobile mass with the property of self-leveling (spot melt of at least 23 cm): a) 30 × 40 cm and 3 and 10 mm thick plates for studying water absorption, crack resistance, uniformity of the material, its color gamut (pigmented compositions) and uniform distribution of color in the sample; b) beams with a size of 16 × 4 × 4 cm to determine the strength of the material. To obtain samples, the mixtures are cast into special molds for curing at a temperature of 20 ± 2 ° C, kept for 7-8 hours, then removed from the mold and left in air at room temperature until a full set of strength.

In tables 1 and 2, respectively, are the compositions and properties of the obtained compositions.

The tables show that the use of caustic brucite as a component of magnesia cement and the indicated stabilizing and modifying additives makes it possible to obtain a self-leveling composition with a pot life of 1 to 4.5 hours, upon curing of which a magnesia stone with high mechanical and decorative properties, low value is formed water absorption. The range of the pot life of the composition allows it to be produced not only in places of direct use, but also remote over significant distances. From the composition it is possible to obtain decorative mechanically durable cast products and structures of almost any shape and size, colored coatings and self-leveling floors with a thickness of 3 to 10 mm and above, as well as use the material for decorative and artistic decoration of elite rooms.

A comparative analysis of the compositions and properties of the obtained composition with the data of the prototype (RU 2163578) showed the following advantages of the proposed technical solution:

- the pot life is from 1 to 4.5 hours, instead of 1 hour in the prototype;

- increased mechanical strength of the composition under compression by 1.5 times;

- the use of caustic brucite as a component of magnesia cement provides higher decorative qualities of the composition, expands the raw material base of magnesia cement and the range of materials based on it;

- the created composition is simpler in composition and does not contain expensive components with a high degree of dispersion (silica flour, silica dust, etc.).

Information sources

1. RF patent N 2130437, class. С04В 9/00, С04В 28/30, С04В 111/20, ЕВВ 33/138 dated 04/06/98 “Raw mix”.

2. RF patent N 2378218, class. СВВ 28/30 dated 02/19/08 "Raw composition for the production of building materials and products."

3. RF patent N 2163578, class. С04В 28/30 from 04/28/2000

"Self-leveling building mixture" (prototype).

All samples are crack resistant. Crack resistance was studied using a light microscope on samples after a full set of strength (28 days) and on samples soaked in water for 4 days.

Claims (1)

Self-leveling magnesia composition containing magnesia cement, consisting of active magnesium oxide and a salt component in the form of an aqueous solution of magnesium chloride, inert filler is quartz or granite sand, a stabilizing and water-retaining additive, as well as a complex modifying additive, characterized in that the magnesia cement is active magnesium oxide contains caustic brucite, and a higher alcohol of the C ₁₂ -C ₁₈ series is taken as a stabilizing and water-retaining additive, while modifying The complexing additive consists of a hydrophobic surfactant in the form of a vinyl chloride / ethylene / vinyl laurate copolymer, or vinyl acetate / versatate / acrylate, or vinyl acetate / vinyl alcohol and hydroxycarboxylic acid in the following ratio, wt.%:
caustic brucite 21.0-31.5 filler - quartz or granite sand 31.5-53.2 stabilizing and water-retaining additive - alcohol of series C ₁₂ -C ₁₈ 0.5-1.8 complex modifying additive: the specified hydrophobic surfactant copolymer 0.5-1.0 hydroxycarboxylic acid 0.2-1.5 salt component - aqueous solution magnesium chloride rest