RU2376260C2 - Method of construction materials manufacture based on magnesium oxychloride cement - Google Patents

Abstract

FIELD: construction. ^ SUBSTANCE: method of construction materials production includes mixing of activated powder based on caustic magnesite, magnesium chloride solution and filler. The activated powder is produced by joint milling to specific surface of particles 4000-20000 cm2/g of magnesite caustic powder, tribasic calcium phosphate, silica gel, methylcellulose and construction gypsum at the following ratio of components, wt %: magnesite caustic powder 40-70, tribasic calcium phosphate 1-8, silica gel 3-12, methylcellulose 0.04-0.6, construction gypsum is the remaining. ^ EFFECT: improved strength and water tightness. ^ 4 cl, 5 tbl

Description

The invention relates to the production of building materials and can be used in the manufacture of dry mixes for construction purposes, in the manufacture of monolithic structures: floors, screeds for various floor coverings, plasters, external and internal, as well as for the manufacture of plates and panels for partitions, internal and external cladding buildings, flooring slabs, staircase slabs, window sills, countertops, wall blocks, extrusion beams, panels, partitions, baseboards, doors, etc.

Known gypsum binders are used in construction as dry mixes (finishing and plastering mortars, self-leveling floors, putties, adhesives, etc.) and products (partition panels, ceiling plates and floors). The expansion of the range of mixtures and products from gypsum binders is caused by the low cost in comparison with cements, high fluidity and formability of mixtures, product uniformity, a high degree of workability, sound and heat insulation properties, and fire resistance. The disadvantages of gypsum binders are relatively low strength and low water resistance.

A known method of manufacturing products on a magnesian binder by mixing caustic magnesite powder with a mineral additive, C-3 superplasticizer, an aqueous solution of magnesium chloride, aggregate, followed by molding and curing of the mixture (RU 2121987.1988).

The method allows to increase the strength of products, but to an insufficient degree, since the stratification of the mixture increases, which is not technologically advanced for prefabricated and monolithic structures.

A known method of increasing the water resistance of magnesia material by the introduction of phosphogypsum and liquid glass modified with urea (SU 1560502, 1990). The proposed method slightly increases the water resistance, but in general the water resistance of the samples on a magnesian binder remains at a low level - 0.50-0.55.

Closest to the claimed one is a method of manufacturing building materials on a magnesian binder, in which caustic magnesite is co-milled with quartz and a superplasticizer, and methylcellulose, copolymer redispersible powder and fiber are added to the magnesite-concrete mixture (RU 2222508, 2004). The method provides an increase in strength and an increase in water resistance of products. However, the use of chemically inert quartz sand as a filler and the absence of phosphates reduces the strength and water resistance of products.

The technical result of the claimed invention is the high strength and water resistance of products on a magnesian binder.

This result is achieved due to the fact that in the method of manufacturing building materials on a magnesian binder, comprising mixing an activated powder based on caustic magnesite, a solution of magnesium chloride and aggregate, the activated powder is obtained by co-grinding to a specific surface of particles of 4000-20000 cm ² / g of magnesite powder caustic, tricalcium phosphate, silica gel, methyl cellulose and gypsum in the following ratio of components, wt.%:

caustic magnesite powder 40-70 tricalcium phosphate 1-8 silica gel 3-12 cellulose 0.04-0.6 gypsum building Rest

As a filler, sand and gravel can be used in the following ratio of components, wt.%:

activated powder 10-18 solution of magnesium chloride in water (density 1.15-1.30 g / cm ³ ) 10-18 sand 15-25 crushed stone Rest

or microspheres and expanded clay gravel in the following ratio of components, wt.%:

activated powder 20-30 solution of magnesium chloride in water (density 1.10-1.30 g / cm ³ ) 20-30 microspheres (p = 0.38 g / cm ³ ) 8-12 expanded clay gravel rest

or as a filler, sand of a fraction of 0.2-0.7 mm is used, and a copolymer redispersible powder is additionally introduced into the mixture in the following ratio of components, wt.%:

activated powder 25-30 solution of magnesium chloride in water (density 1.10-1.30 g / cm ³ ) 20-30 copolymer redispersible powder 0.01-1.0 sand rest

Thus, the activation of caustic magnesite powder is performed with gypsum, tricalcium phosphate, silica gel and methyl cellulose. A magnesite-concrete mixture is then prepared by mixing the activated powder, magnesium chloride and aggregate.

While stirring the magnesite-concrete mixture, a pigment (2-5% by weight of the activated powder), copolymer redispersible powder (0.1-1%) and fiber (3-5%) can be added to it.

Inorganic and / or organic aggregate can be added to the activated mass in an amount of 1-90% by weight of the final mixture.

The magnesia mixture is formed, depending on its consistency, using one of the following known methods: casting (standard cone precipitate / OK /> 18 cm); vibration exposure (2 <OK <15); tamping, pressing, vibropressing (hard mixes). When installing monolithic floors, the use of bulk mixtures, vibrating rails, evacuation, smoothing, grouting, etc.

Curing of products can be carried out both in natural normal conditions and in heat treatment. During heat treatment, an additional increase in strength and water resistance occurs. This is due to the property of magnesite concrete made by the proposed method to withstand thermal deformations (damping effect from the use of additives and joint grinding).

The difference from the known methods is not just the combined use of magnesia binder, gypsum and additives, but the use of activated gypsum-magnesia powder with a multifunctional effect, significantly superior to the effects of the known methods.

As a result of the activation of co-grinding of magnesite caustic and gypsum powder during mutual chemisorption, both magnesite and gypsum particles are activated, which further not only increases the speed and completeness of hydration reactions, but also contributes to the formation of new complex compounds based on magnesium oxysulfates and oxychlorides. Joint grinding also increases the degree of hydrolysis and the activity of PO ₄ ^3- .

With the joint grinding of silica gel and magnesite powder during mutual chemisorption, magnesite particles are activated, which further increases the speed and completeness of hydration reactions and ensures the preferential formation of a more stable phase - magnesium trioxychloride. Joint activation also promotes the chemical bonding of magnesium hydrochlorides with a silicate substrate, providing the formation of high-strength water-insoluble compounds. In addition, when grinding silica gel, Si-O-Si bonds are partially destroyed with the formation of -O-Si bonds, which accelerates the interaction of silicates with magnesium hydroxide, and this process is further enhanced in the presence of silicic acid.

The addition of methyl cellulose (cellulose esters) to cement mixtures increases the adhesive and water-holding capacity of the cement paste, and allows the rheological characteristics of the cement paste to be controlled and, accordingly, the form stability and elasticity of the system. In addition, the addition of methyl cellulose reduces macroporosity and promotes the formation of a microporous structure of magnesia stone, which reduces internal stresses and increases strength. The introduction of methyl cellulose eliminates sedimentation of magnesia dough, phase separation of the dough and water separation, sharply increases the uniformity of the formed stone, provides similar properties for magnesite concrete mixtures and magnesite concrete with any aggregates.

The addition of silica gel increases the strength and density of magnesia stone, which is associated with a chemical reaction between silica and magnesium hydroxide. The reaction products fill the pores and also strengthen the contact zones in magnesia concrete.

The addition of copolymer redispersible powders based on vinyl acetate and versatate increases the adhesive ability of the magnesia test, providing high adhesion between magnesite concrete and the base, as well as between the individual layers of magnesite concrete. This is especially important when building monolithic magnesian solid floors. The introduction of these additives in the composition of bulk floors on mineral binders improves the rheological characteristics of the mixture, which increases the spreadability, the ability to self-level and the formation of a smooth smooth surface. In addition, copolymer redispersible powders are well compatible with other additives used for the production of self-leveling masses (superplasticizers, etc.).

The introduction of fiber (polymer or glass fibers) into magnesite-concrete mixtures provides an increase in impact strength and fracture toughness of magnesite-concrete as a result of a sharp decrease in cracking processes and an increase in tensile and bending strength. In addition, the microreinforcing of magnesite concrete with fibers additionally increases its wear resistance.

Both inorganic and organic aggregates can be used as fine (0-5 mm) and coarse (5-40 mm) aggregate. The size of the particles of coarse aggregate should be no more than 1/3 of the thickness of the manufactured products.

The following are used as inorganic aggregate: granite crushed stone, quartz sand, crushed stone, gravel and sand of other rocks; gravel and sand mixture, building sand; crushed stone, gravel and sand; talc; marble, limestone, granite chips; crushed brick, concrete, light aggregates and sowing light aggregates for concrete; crushed slags and sieving of slags of metallurgical and chemical industries that do not contain harmful impurities; flutter waste; asbestos; crushed slag pumice.

The following are used as organic aggregate: wood flour, sawdust, shavings and wood chips of coniferous and deciduous species; shredded guzapaya and cotton stalks; chopped straw; crushed bonfire of flax, kenaf, hemp; shredded tow of fiber flax, kenaf, hemp; rice, millet, barley, sunflower husk, tow and cotton lints, paper waste, etc. The particle size of the organic aggregate depends on the thickness of the manufactured products (not more than 1/3 of the thickness).

Floors and products on a magnesian binder are made of various colors using for coloring by introducing into the composition with stirring the magnesite-concrete mixture alkali-resistant mineral building pigments: chalk, minium, ocher, chromium oxide, titanium oxide, zinc oxide, ultramarine, soot, umber, manganese oxide, phthalocyanine pigments, etc.

The following materials were used as initial components (components) of the mixture of building products.

Caustic magnesite powder ПМКМк - 75, ПМКМк - 83 or ПМКк-87 produced by OJSC "Plant Magnesite" (Satka, Chelyabinsk Region). Chemical composition according to GOST 2642.2-86 ... 2642.8-86 is presented,%: MgO 78.9; CO ₂ 3.85; CaO 3.24; H ₂ O 1.85; SiO ₂ 3.28; (Al ₂ O ₃ + Fe ₂ O ₃ ) 2.65; SO ₄ 0.20; p.p. - 6.03. Powder density 3.29 g / cm ³ , residue on sieve No. 02-3.6%, passage through mesh No. 009 - 88.3%. Start of setting 0-45 minutes, end - 4-12 min All indicators correspond to GOST 1216-87.

Technical magnesium chloride (bischofite) according to GOST 7759-73 produced by PA Kaustik (Volgograd), the dry matter content of MgCl ₂ × 6H ₂ O is 93.8%. An aqueous solution of magnesium chloride was applied with a density of 1,100-1,310 g / cm ³ .

Microspheres - manufacturer: TPP No. 22 (Moscow region). Physical properties: bulk density 0.3735 g / cm ³ ; humidity ≈ 8%; strength ≈ 20 MPa; fraction ≈ 50-150 microns; impurities> 1 mm ≈ 1-2% by weight; Mohs hardness 5-6; melting point 1300 ° C; pH in water is 6-8.

Microspheres (cenospheres) are small hollow solid particles that are formed as a part of fly ash during coal burning at thermal power plants. Fly ash (slag) after burning coal is pumped into pits filled with water, where light and heavy fractions are separated. Light particles (microspheres) with a density of 0.40-0.70 g / cm ³ float to the surface. Microspheres serve as a filler in the manufacture of products from plastics, gypsum, ceramics, lightweight cements, and other building materials. Products with the addition of microspheres have increased wear resistance, lightness and high insulating properties. In addition, the use of microspheres as fillers significantly reduces the cost of production.

Building plaster of the G-5 brand of the Perm factory according to GOST 125-79. Properties of building gypsum: gypsum grade according to GOST 125-79 G-5 A111; true density 2.44 g / cm ³ ; the residue on sieve No. 02 - 1.4%; specific surface area according to PSH-2 - 320 m ² / kg.

Methyl cellulose — Tylose MH 60010P4, Walocel MKX 400PP 20, Culminal C 8350 and Culminal C 8564, which are instant cellulose esters, were used as additives based on cellulose esters. "Tylose MH 60010P4" is manufactured by the company "Clariant GmbH" (Germany). Walocel MKX 400PP 20 is manufactured by Wolff Walsrode (Bayer) (Germany). Culminal C 8350 and Culminal C 8564 are manufactured by Aqvalon (Germany).

Fiber was used in two types. The first one is chopped glass thread of the EU-10 TW 5 and EU-10 TW 10 brands, manufactured by OJSC Tverstekloplastik according to TU5952-052-00204961-98. The length of the filament was 5 and 10 mm, respectively, diameter was 9.7 microns, and the content of SiO ₂ was 53-54.8%. The second type is polypropylene monofilament Fibrin 23 (FIBREX) of the company "Business and Building System Group SPB" with a length of 6 mm and a diameter of 18 microns.

The following two groups of finished products with highly adhesive adhesive ability were used as additives of copolymer redispersible powders:

First group:

"DM 1140P" is a vinyl acetate / ethylene monomer system;

“LDM 202 IP” is a vinyl acetate / versatate monomer system;

"LDM 2080" is a vinyl acetate / versatate / acrylate monomer system.

All additives of the first group are water-soluble powders of film-forming adhesives, manufactured by Clariant GmbH (Germany).

The second group is represented by Vinnapas dispersion powders based on a copolymer of vinyl acetate and ethylene: Vinnapas RE 523 Z; Vinnapas RE 525 Z; Vinnapas RE 5011 L. All additives of the second group are manufactured by Wacker Polimer Sistems GmbH & Co.KG (Wacker-Chemie GmbH).

Comparative tests were carried out on magnesite concrete samples without additives (control composition), samples obtained by the analogous method and samples in accordance with the invention.

Table 1 The components of the activated powder according to the proposed method Components No. of compounds one 2 3 four 5 Magnesite powder 40,0 47.5 55.0 62.5 70.0 Tricalcium phosphate 1,0 2,4 3.8 5.2 6.6 Kremnegel 3.0 5.0 7.0 9.0 11.0 Cellulose 0.1 0.2 0.3 0.4 0.5 Gypsum plaster 55.9 44.9 33.9 22.9 11.9

No additional control composition (0). The magnesite-concrete mixture was prepared by mixing magnesite powder (15%), coarse and fine coater, and an aqueous solution of magnesium chloride.

Analogue (a). The activated powder was prepared by joint grinding of caustic magnesite powder in an amount of 70%, superplasticizer C-3 in an amount of 1% and quartz sand in an amount of 29% to a specific surface of 12000 cm / g. The activated powder was introduced into the magnesite-concrete mixture in an amount of 15%.

The proposed method (p). The activated powder was prepared by co-grinding the components indicated in Table 1 to a specific surface of 12,000 cm ^{2 /} g. The activated powder was introduced into the composition of the magnesite-concrete mixture in an amount of 15%.

A method of manufacturing building products on a magnesian binder consists in preparing, dosing and mixing caustic magnesite powder (activated for the proposed method and for an analog; non-activated for control) with aggregates followed by mixing with magnesium chloride with a density of 1.10-1.30 g / cm ³ with stirring until a homogeneous concrete mixture is obtained. The density of the bischofite working solution was calculated from the content of active MgO. The laid mixture was leveled, compacted by vibration (3 s), after which it was cured at a temperature of 20 ± 2 ° C for 10 hours. Then the samples were unformed and stored under the same conditions for 28 days.

Bending and compression strengths are determined according to GOST 18105-86. The water resistance coefficient is defined as the ratio of the compressive strength of 28-day-old samples aged 3 days in water to the strength of control samples.

The compositions of the mixtures and the results of testing the strength and water resistance of magnesite concrete are shown in Table 2.

Analysis of the data showed an undoubted advantage of the proposed method in the entire range of activated powder compositions. Compounds No. 3, 4 have a particularly clear advantage - the compressive strength is higher by 50% of the control, by 28% of the analogue; bending strength - respectively 80 and 40%; water resistance - by 40 and 15%.

table 2 Type of powder Components, wt.% Strength, 28 days Coef. water resistance Powder Bischofite solution Density, g / cm ³ Sand Crushed stone Compression Bend PMK counter. fifteen fifteen 1.24 twenty fifty 40.5 7.4 0.58 Analogue fifteen fifteen 1.22 twenty fifty 47.8 9.3 0.72 No. 1 fifteen fifteen 1,165 twenty fifty 51.5 9.9 0.70 Number 2 fifteen fifteen 1.185 twenty fifty 56.0 10,4 0.80 Number 3 fifteen fifteen 1,210 twenty fifty 61.2 13,2 0.82 Number 4 fifteen fifteen 1,225 twenty fifty 60.8 13.5 0.80 Number 5 fifteen fifteen 1,245 twenty fifty 54.5 13.0 0.72

Next, the product compositions were prepared according to the control method (o), the analogue method (a) and the proposed method (p).

No additional control composition (0). The magnesite-concrete mixture was prepared by mixing magnesite powder in an amount of 10-18%, coarse and fine coater, and an aqueous solution of magnesium chloride.

Analogue (a). The activated powder was prepared by co-grinding the caustic magnesite powder in an amount of 70%, C-3 superplasticizer in an amount of 1% and quartz sand in an amount of 29% to a specific surface

12000 cm ² / g (composition of the greatest strength). The activated powder was introduced into the composition of the magnesite-concrete mixture in an amount of 10-18%.

The proposed method (p). The activated powder was prepared by co-milling the caustic magnesite powder in an amount of 50%, tricalcium phosphate in an amount of 4%, silica gel in an amount of 8%, methyl cellulose in an amount of 0.40%, gypsum gypsum in an amount of 37.6% to a specific surface of 12,000 cm ² / g. The activated powder was introduced into the composition of the magnesite-concrete mixture in an amount of 10-18%.

Compositions for the manufacture of products according to the control method (k), the method of analogue (a) and the proposed method (p) and the results of comparative tests are shown in Table 3.

Analysis of the data shows the advantages of the proposed method. The compressive strength at the age of 28 days is 20-30% higher compared to the analogue, 30-40% higher than the control non-additive magnesite concrete, tensile bending - 20-45 and 70-90%, respectively, and water resistance coefficient - by 10-20 and 30-40%.

A visual improvement in the uniformity of the mixture and the surface quality of the samples according to the proposed method was also noted.

The compositions of lightweight concrete products obtained by the control method (o), the analogue method (a) and the proposed method (p) are shown in Table 4.

Analysis of the data shows the advantages of the proposed method for lightweight concrete products. The compressive strength at the age of 28 days is 20-30% higher than that of the analogue, 30-40% higher than the control non-additive magnesite concrete, tensile bending - 20-45 and 70-90%, respectively, and water resistance coefficient - by 10 -20 and 30-40%.

A visual improvement in the uniformity of the mixture and the surface quality of the samples according to the proposed method was also noted.

For a mortar bulk magnesia mixture (compositions are shown in Table 5), the increase in strength according to the proposed method compared to the analogue was 15–20% in compressive strength, 30–50% in tensile bending, and 15–30% in water resistance.

Thus, it was found (Tables 2-5) that the proposed method for the manufacture of building products on a magnesian binder has advantages over the analogue method for all types of materials on a magnesian binder.

Claims (4)

1. A method of producing building materials on a magnesian binder, comprising mixing an activated powder based on caustic magnesite, a solution of magnesium chloride and aggregate, characterized in that the activated powder is obtained by co-grinding to a specific surface of particles of 4000-20000 cm ² / g of caustic, tricalcium phosphate magnesite powder , silica gel, methyl cellulose and gypsum in the following ratio of components, wt.%:
caustic magnesite powder 40-70 tricalcium phosphate 1-8 silica gel 3-12 cellulose 0.04-0.6 gypsum building rest 2. The method according to claim 1, characterized in that sand and gravel are used as aggregate in the following ratio of components, wt.%:
activated powder 10-18 solution of magnesium chloride in water density 1.15-1.30 g / cm ³ 10-18 sand 15-25 crushed stone rest 3. The method according to claim 1, characterized in that the microspheres and expanded clay gravel are used as a filler in the following ratio of components, wt.%:
activated powder 20-30 solution of magnesium chloride in water density of 1.10-1.30 g / cm ³ 20-30 microspheres p = 0.38 g / cm ³ 8-12 expanded clay gravel rest 4. The method according to claim 1, characterized in that the sand fraction of 0.2-0.7 mm is used as a filler, and a copolymer redispersible powder is additionally introduced into the mixture in the following ratio of components, wt.%:
activated powder 25-30 solution of magnesium chloride in water density of 1.12-1.30 g / cm ³ 20-30 copolymer redispersible powder 0.01-1.0 sand rest