RU2286965C1 - Method of manufacturing magnesia binder - Google Patents

Abstract

FIELD: manufacture of building materials.

SUBSTANCE: invention, in particular, relates to manufacturing magnesia binder from high-magnesia rocks: magnesite and brucite containing magnesium hydrosilicates, such as serpentinites, ultrabasites, etc., and also from intentionally composed blend of magnesite with naturally occurring magnesium hydrosilicates. In particular, high-magnesia rocks containing 15-40% magnesium hydrosilicates are crushed into fraction below 60 mm, which is fired for 2-3 h at 1050-1100^oC and then ground into powder, 78-84% of which pass through screen no. 008. Invention can be used in manufacture of slabs and panels for interior facing of buildings, stools, stair steps, and also for manufacturing dry building mixes, heat-insulation materials and articles, and for forming cast-in-place floors.

EFFECT: enabled manufacture of high strength magnesia binder with no trend to cracking and having low linear shrinkage upon solidification, and extended resource of raw materials for magnesia binders.

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Description

The invention relates to the production of building materials, and in particular to a method for producing magnesian binders from waste materials for the production of magnesian refractories, including high-magnesian rocks (magnesite or brucite) and magnesium hydrosilicates - serpentinites, ultrabasites, etc., as well as from a specially formulated charge magnesite with natural magnesium hydrosilicates.

Known raw material mixture to obtain a binder (RU 937396, 04 V 9/06, 1982), containing serpentinite and limestone in the following ratio, wt.%:

Limestone 63 ... 67 Serpentinite 33 ... 37

The firing of this mixture is carried out in a rotary cement kiln at 1400 ° C. The resulting system contains active dicalcium silicate and magnesium oxide mainly in the active form and partially in the bound state in the form of forsterite and magnesioferrite. The specified magnesia cement has a fairly high strength, but requires high firing temperatures (up to 1400 ° C), has a very significant linear shrinkage, in addition, this binder is most effective in the manufacture of refractories.

Also known is the raw material mixture for the manufacture of magnesia binder (RU 2089523, C 04 B 9/00), including dolomite and serpentinized ultrabasite in the following ratio, wt.%:

Dolomite 40 ... 80 Serpentine Ultrabasite 20 ... 60.

The specified mixture is fired at a temperature of 780 ° C for 2 hours. The technical result achieved by using the invention is to reduce the setting time and increase adhesion to wood.

The disadvantage of this solution is the low strength of the stone obtained during hardening of the binder, as well as the limitation of the area of use of the obtained binder (use only in the manufacture of wood-mineral products), which may be associated with high shrinkage in the forming stone during hardening of the binder and cracking in the hard system.

Known astringent (SU 1433924, 04 04 9/00), including components in the following ratio, wt.%:

Magnesium oxide 25-45 Burnt Serpentine 47-67 Magnesium Chloride or Sulfate rest.

This binder provides excellent strength and linear shrinkage during curing. The disadvantage is the additional energy costs for firing serpentine.

Closest to the claimed invention is the method according to patent RU 2245862 (C 04 B 35/03, C 04 B 9/06).

Sludge waste from talc production, containing 73% magnesite, 20% talc, 5% chlorite and 2% other minerals, after rough cleaning, crushing and sorting to a fraction of 0 ... 20 mm, is subjected to preliminary drying, then calcined for 3 hours in an oven at 900 ° C, grind into powder to a fraction of 0.08 mm to obtain magnesia binders. The resulting binder meets the requirements of GOST 1216-87. This method is considered economical, non-waste and environmentally friendly.

However, requirements for binders used in construction are different from the requirements for binders for refractory materials. In addition, data on the quality of products made from the obtained materials are not presented: strength, tendency to crack formation during hardening and the magnitude of linear deformations. The claimed invention solves the problem of obtaining magnesian binder for construction purposes from magnesian rocks with a high content of serpentinite, not suitable for the production of refractories, which has high strength, is not prone to cracking and has low linear shrinkage during hardening.

This goal is achieved due to the fact that in the method for producing magnesian binder high-magnesian rocks containing hydrosilicates-serpentinite 15-40 wt.% Are used as raw materials, which are crushed to a fraction of less than 60 mm, calcined at a temperature of 1050-1100 ° С for 2-3 hours, then grind into powder until passing through a sieve 008 - 78-84 wt.%.

Crushing the rock to a fraction of less than 60 mm ensures the least loss of material during subsequent firing in a rotary kiln.

Firing at a temperature of 1050-1100 ° C for 2 ... 3 hours provides obtaining a magnesian binder of average activity, characterized by high strength indicators, small linear shrinkage and lack of tendency to cracking.

The heat treatment of these magnesian rocks at lower temperatures (with firing times up to 6 ... 8 hours) leads to the formation of an astringent high activity, prone to cracking in the initial stages of hardening and when exposed to water.

An increase in the temperature and firing time leads to a decrease in the activity of the main component of the binder - magnesium oxide due to its crystallization and transition to periclase, which can cause cracking of products based on the binder obtained in the later stages of air hardening (this phenomenon can manifest itself within a year) or storing samples in water (for 7 days).

The chemical composition of the source rocks is shown in table 1, mineralogical - in table 2.

Table 1 Breed The content of oxides, wt.% MgO Fe ₂ O ₃ Cao SiO ₂ RFP Brucite 54 ... 68 0,1 ... 0,2 3.3 ... 6.8 2.1 ... 5.6 26 ... 33 Magnesite 42 ... 47 0.5 ... 1.2 0.5 ... 4.7 0.1 ... 4.8 49 ... 53 table 2 Breed The content of minerals, wt.% Brucite Magnesite Dolomite Calcite Magnesium Hydrosilicates Brucite 57 ... 80 Traces ... 6 Traces ... 7 Traces ... 8 15 ... 30 Magnesite - 52 ... 75 Traces ... 5 Traces ... 6 20 ... 40

The characteristics of the proposed magnesia binders are presented in table 3.

From the data presented in the table it can be seen that the rocks of magnesite and brucite, including serpentinites in the amount of 15 ... 40%, provide high-quality binder only as a result of firing at 1050 ... 1100 ° C and aging at the indicated temperatures for at least 2 and not more than 3 hours. The rocks, including minor impurities of iron, such as brucite, after firing form a binder with high whiteness, which allows us to recommend its use for decorative decorative materials, mineral paints, and putties.

To obtain building products, the binder is thoroughly mixed with aggregates or without them for 1 ... 3 minutes and with an aqueous solution of magnesium chloride (bischofite) with a density of 1.2 g / cm ³ in an amount that provides cast mobility of the mixture, the mixture is poured into molds and leave to harden at temperatures not lower than 10 ° C, preferably at 20 ... 25 ° C.

The invention allows to expand the raw material base for the production of magnesia binder, including by recycling refractory production waste. The invention can be used in the manufacture of plates and panels for the inner cladding of buildings, window sills, stair steps, as well as for the production of dry building mixtures, heat-insulating materials, monolithic floors, etc.

Table 3 No. Breed Firing mode Properties pass through a sieve 008,% Cracking tendency * R *, * MPa Δ ***,% color one Brucite 700 ° C for 2 hours 76 Samples crack and break into blocks when air cured - white 2 Magnesite 81 Samples crack and break into blocks when air cured - Gray 3 Brucite 800 ° C for 2 hours 78 Samples crack and disintegrate into blocks when air cured - white four Magnesite 83 Samples crack and break into blocks when air cured Gray 5 Brucite 900 ° C for 2 hours 75 Samples crack and break up into blocks after 1 day of storage in water 24 white 6 Magnesite 82 Samples crack and break up into blocks after 1 day of storage in water twenty 0.42 Gray 7 Brucite 1000 ° C 2 hours 78 Samples crack and break up into blocks after 1 day of storage in water 56 0.21 white 8 Magnesite 82 Samples crack and break up into blocks after 1 day of storage in water 55 0.18 Gray 9 Brucite 1050 ° C for 2 hours 78 Samples do not crack when stored for more than 7 days in water 74 0,03 white 10 Magnesite 80 Samples do not crack when stored for more than 7 days in water 77 0,025 Gray eleven Brucite 1100 ° C 2 hours 9 Samples do not crack when stored for more than 7 days in water 74 0,027 white 12 Magnesite 2 Samples do not crack when stored for more than 7 days in water 75 0,032 Gray 13 Brucite 1200 '' 'From 2 hours 2 Samples have separate through cracks when stored for more than 2 days in water 42 - white fourteen Magnesite four Samples have separate through cracks when stored for more than 2 days in water 39 - Gray * lozenges made of normal density cement paste

** compressive strength of 2 * 2 * 2 cm cubed samples made of cement paste of normal density, determined at 28 days of air hardening *** deformation (linear shrinkage) of samples in 56 days of air hardening

Claims (1)

A method of producing a magnesian binder, characterized in that high-magnesian rocks containing 15-40 wt.% Magnesium hydrosilicates are crushed to a fraction of less than 60 mm, calcined at a temperature of 1050-1100 ° C for 2-3 hours, then ground to a powder - passage through a sieve 008 - 78-84%.