RU2374206C1 - Raw mixture for making ceramic objects - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to production of ceramic objects for construction purposes and can be used in making bricks, building tiles, roofing tiles, large-sized wall blocks, paving objects. The raw mixture for making ceramic construction objects contains natural sand, blast-furnace and/or steel-smelting slag, where SiO₂ content in the mixture lies between 70 and 85%, with the following ratio of components, wt %: natural sand - 60 to 80; blast-furnace slag - 0 to 40; steel-smelting slag - 0 to 40; soluble glass - 0 to 5. The method of making ceramic construction objects from the said raw mixture involves preparation of the raw mixture, moulding objects and calcination. The raw mixture undergoes combined grinding to particle size of 20 to 50 mcm. Moulding is done at pressure ranging from 35 to 150 MPa, and calcination is done in the following procedure: raising temperature to 500°C at a rate of 150 to 200°C/hour, then to 1050 to 1150°C at a rate of 65 to 150°C/hour, maintaining temperature of 1150°C for 1 to 2 hours, and then cooling at a rate of 100 to 150°C/hour.

EFFECT: increased compression strength and frost-resistance of the material, use of natural sand as the main component of the raw mixture and recycling various wastes (blast-furnace and steel-smelting slag).

2 cl, 3 tbl, 1 ex

Description

The present invention relates to the production of ceramic products for construction purposes and can be used in the manufacture of bricks, ceramic stones, tiles, large-sized wall blocks, paving products.

A large number of inventions are known (Patents RU 2194680, 2284307, 2304123, 2287504) related to the compositions of ceramic mixtures and methods for the production of ceramic products based on them, but one of the main components in the composition of the raw mix is clay. One of the objectives of the invention is the exclusion of the clay component from the mixture.

A known raw material mixture comprising a quartz component in the form of wastes from the enrichment of ferruginous quartzites or muscovite mica, a nepheline additive in the form of nepheline concentrate or wastes from the enrichment of apatite-nepheline ores, cullet and sulphite-alcohol bard at a particle size of less than 0.05 mm and their ratio, wt.% : enrichment waste for ferruginous quartzite or muscovite mica 69.85-79.32, nepheline concentrate or enrichment waste for apatitenefelin ores 7.26-10.83, cullet 8.36-22.38, sulphite-alcohol stillage 0.5-5.0. The use of ceramic mass allows to obtain wall brick products having a porosity of 40.7-44.2% and a thermal conductivity of 0.29-0.32 W / m · K, bending strength of 4.5-8.3, compressive strength of 31-46 MPa, water absorption of 20.3-21.6% (Patent RU 2230047 )

Also known is the invention used in the manufacture of bricks, ceramic stones, tiles, large blocks. According to the invention, the manufacture of building products is carried out by preparing a molding mass, consisting, wt.%: 0.1-50.0 sand, 3.4-15.0 calcium oxide, 0.1-4.0 curing activator in the form of caustic or calcined soda, ammonium salt or mixtures of these substances, into which 0.1-4.0 sodium silicate is introduced in the form of water glass, and clay, plastic molding of products and their heat treatment, including the stages of preliminary drying to a moisture content of 10.0-11.5% at a temperature of 60-70 ° C, heat-moisture treatment in a closed atmosphere saturated steam at a temperature of 100-105 ° C for two hours and subsequent drying with a gradual decrease in humidity. Subsequent drying is carried out in the process of a gradual rise in temperature from 105-130 ° C for 8-10 hours to a residual moisture content of 1.0-1.5%. The molding material is prepared in three stages: at the first stage, preliminary mixing of the components of the molding mixture is carried out, at the second stage, it is aged for 12-24 hours until quenching of calcium oxide and clay hydrolysis are completed, and at the third stage, the molding mixture is finally processed to impart homogeneity, feeding into a vacuum press after fine grinding and grinding. The implementation of the claimed invention allows to reduce the cost of production and improve the quality of products (Patent RU 2225379).

The disadvantage of analogues is the complexity of the process and insufficiently high strength characteristics of the obtained ceramic products.

The closest analogue of the claimed invention is a molding mass of silica-containing binder, which is used as an alkali metal or ammonium hydroxide, and silica-based aggregate, which is used as river, sea, quarry sand, granite, basalt, etc. (Patent RU 2283818). The disadvantage of this analogue is the use of alkali-containing hydroxides that require special alkali-resistant lining of equipment and reduce the water resistance of the resulting building products.

Closest to the proposed raw mix and method of manufacturing ceramic products according to the technical nature and the achieved effect are the raw mix and manufacturing method according to patent RU 2287501.

According to the patent, the raw material mixture contains silica fume and an aluminosilicate component, which is used as a heat-treated carbonized loam with a CaO + MgO content of 10-11%, as well as carbon-containing Al-production waste - electrostatic dust, with the following ratio of components, wt.%:

silica fume 60.9-70.5 heat treated loam 20.4-26.1 dust of electrostatic precipitators 9.1-13.0

The disadvantage of the prototype is the relatively low values of compressive strength (18.4-27.2 MPa) and frost resistance (85-175 cycles) of the material and high values of water absorption (28.0-38.5%).

The objective of the present invention is to develop the composition of the ceramic mixture and the creation of a method that allows to obtain ceramic material for construction purposes with increased strength properties, while also setting the goal of using natural sand as the main component, since the building material is intended for regions poor in other raw materials (in in particular, regions of the Far North), and the disposal of various production wastes (blast furnace and steelmaking slag, ash and slag TPP).

The technical result is achieved in that the proposed raw material mixture contains silica and aluminosilicate components and is characterized in that in order to provide increased compressive strength up to 130-160 MPa, it includes various natural sands as silica-containing component - quartz, river, marine, building, as aluminum-containing component blast furnace and / or steelmaking slag, and the content of SiO ₂ in the mixture is at least 70-85% in the following ratio of components, wt.%:

natural sand 60-80 blast furnace slag 0-40 steelmaking slag 0-40 soluble glass 0-5.

Used natural sand contains SiO _{2 of} at least 93%, aluminum oxide in the amount of 2%, oxides of iron, titanium, potassium, calcium can be present in the sand. A quartz-like solid solution based on high-temperature quartz is present as the main crystalline phase; inclusions of kaolinite, feldspar, and rutile are found. The granulometric composition of sand is represented by grains depending on the type of sand from 100 to 300 microns, according to laser dispersion analysis, the specific surface area of grains is from 0.075 to 0.3 m ² / g.

Blast furnace slag has the following chemical composition, wt.%: SiO ₂ - 42.5; Al ₂ O ₃ - 8.0; CaO - 42.6; MgO - 4.4; Fe ₂ O ₃ - 0.4; SO ₃ - 2,1, is basically a glassy mixture of coarse and fine fractions of light gray in color from 1 to 30 mm. According to the petrographic analysis, the glass content in the sample is 99.0%; inclusions of ore mineral, probably magnetite and a silicate phase of plagioclase of technogenic origin, are found. Large pieces have a porous structure and a conchoid fracture.

Steelmaking slag is a heterogeneous mixture in size and composition. The size of the pieces is from 1 to 20 mm, partially magnetic. Pieces of a porous structure prevail. It has the following chemical composition, wt.%: SiO ₂ - 36.8; Al ₂ O ₃ - 5.4; CaO - 33.1; MgO - 5.5; Fe ₂ O ₃ - 13.2; SO ₃ - 0.6.

According to the petrographic analysis, the slag has a mainly crystalline structure, heterogeneous and complex in mineralogical composition. The X-ray phase analysis revealed the abundance of crystalline phases present in the steelmaking slag: there is quartz with d = 3.58, as in quartz sand, pyroxene solid solutions similar in composition to diopside, fayalite, wollastonite, and magnetite γ - Fe.

The choice of metallurgical slag is due to the fact that during sintering upon receipt of ceramic products, the slag provides a liquid-phase sintering mechanism, due to the fact that blast furnace slag is a vitreous phase, which at the early stage of sintering becomes liquid, and steelmaking slag due to a significant amount of iron oxides It melts at sintering temperatures and also plays the role of a component that envelops grains of sand and binds them in the future into a strong monolith.

It is advisable to increase the strength of the raw material to use a silicate block in an amount up to 5%. When preparing the raw mix, it is desirable that its moisture content is 3-5%.

The combination of quartz sand, blast furnace and / or steelmaking slag with the addition of soluble glass causes the formation of high-strength durable ceramic products when firing using the proposed method.

Closest to the proposed method according to the technical essence and the achieved effect is the method according to patent RU 2287501, which includes preparing a raw mix, molding, drying, firing the product at a temperature of 875 and 950 ° C, characterized in that before preparing the charge carbonized loam is crushed and subjected to heat treatment at 500 ° C. The disadvantage of the prototype is that according to the above method, ceramic materials are obtained having relatively low values of strength and frost resistance and high values of water absorption.

The technical result of the proposed method is achieved by pre-conducting joint grinding of the raw material mixture to a dispersion of 30-50 microns, pressing is carried out at a pressure of at least 35-150 MPa, firing is carried out according to the following mode: heating to 500 ° C at a speed of 150-200 ° C / hour, then to 1050-1150 ° C at a speed of 65-150 ° C / hour, holding at a firing temperature of 1-2 hours, cooling at a speed of 100-150 ° C / hour.

The achievement of the claimed technical result is confirmed by the following examples. The compositions of the raw mixes are shown in table 1.

Example 1

To prepare the raw material mixture, natural sand from the Far North region and blast furnace slag of the metallurgical plant are used. Dose the components in a ratio of 60/40 and carry out their joint grinding in a planetary mill with corundum balls to a specific surface of 1.5 m ² / g with a predominance of particles with a size of 20 μm. The resulting mixture is moistened with water to a moisture content of not more than 3%, and samples are formed by semi-dry pressing at a pressure of 150 MPa to determine bending strength, compressive strength, ceramic properties, and frost resistance. The firing is carried out according to the following mode: raising the temperature to 500 ° C at a speed of 200 ° C / h, then to 1150 ° C at a speed of 150 ° C / h, holding at 1150 ° C for 1 hour, cooling at a speed of 150 ° C / h .

Other embodiments of the invention are disclosed in tables 1, 3.

Table 1 The composition of the raw mixes No. Sand Blast furnace slag Steel Slag Soluble glass one 60 40 - - 2 60 40 - 3 3 70 thirty - - four 70 thirty - 5 5 85 fifteen - - 6 70 - thirty - 7 70 fifteen fifteen -

The selected combinations of raw materials (silica sand and blast furnace slag, silica sand and steelmaking slag, silica sand and a mixture of slag: blast furnace and steelmaking) in the ratio of 60/40 and 70/30 in the presence and presence of soluble glass provide ceramic products with strength on bending above 70 MPa and compressive strength above 130-160 MPa, water absorption below 1%, as evidenced by the data in table 2. The presence of soluble glass in the raw mix increases the strength of the raw material and reduces the percentage of rejects.

The amount of sand above 80% leads to a decrease in the strength characteristics of the resulting material.

The sand content in the raw material mixture of less than 60% does not meet the intended purpose.

table 2 Strength and ceramic properties of materials obtained on the basis of the inventive ceramic mixtures of the present method Mix No. Type of grinding S mixture
m ² / g Firing ° C σ _bending , MPa σ _compression , MPa Density, kg / m ³ Water absorption,% Frost-resistant
bone cycles one joint 1,5 1150 80 160 2470 0.3 250 one separated 1150 43 105 2000 15.0 150 2 joint 1.35 1150 85 150 2450 0.4 - 3 joint 1,5 1150 70 135 2300 0.7 - four joint 1.4 1150 65 145 2350 1,0 - 5 joint 1,6 1150 40 102 2010 12.5 - 6 joint 1.42 1050 75 158 2400 0.8 - 7 joint 1.55 1100 87 165 2430 0.25 270 Proto-
type of 950 22.8 1340 33.1 175

The selected range of firing temperatures ensures the participation of the liquid phase in the sintering processes, which gives the final material high ceramic and strength properties.

When using blast furnace slag, the firing temperature should not be higher than 1150 ° С, since at higher temperatures (1200 ° С and higher) foaming and fusion of the samples are observed. At temperatures below 1050 ° C, complete sintering does not occur and the _bending σ does not exceed 30 MPa.

When using steelmaking slags, the firing temperature should not be higher than 1100 ° С, at a higher temperature they melt.

Table 3 Effect of firing temperature on the strength and ceramic properties of the materials obtained No. T-firing, ° C Bending Strength, MPa Water absorption,% Porosity,% Density, kg / m 1-a 1000 23.0 18.6 36.0 1900 1-b 1050 31,0 13.0 25.6 1970 1-in 1100 51.5 10,4 23.5 2250 1 g 1150 80 0.3 0.75 2470 1-d 1200 Foaming and melting of a sample

An important technological parameter is the rate of temperature rise in the sintering interval, determined by high-temperature dilatometry. At a speed of less than 65 ° C / hour, it is energetically disadvantageous to conduct the regime; at a rate of rise above 150 ° C / hour, product shrinkage unevenly takes place. This is especially important for bulky products.

Thus, the claimed composition and method have the following advantages:

- provide ceramic materials with high strength characteristics and frost resistance;

- use a cheap, non-deficient raw material component - natural sand (river, sea, building, quartz) in an amount of at least 60%;

- industrial waste - blast furnace and steelmaking slags are introduced into the composition of the raw material mixture as a binder grain of sand;

- open up the possibility of creating the production of ceramic products for construction purposes in regions poor in raw materials, in particular in the regions of the far North of Russia, and exclude expensive transportation.

Claims (2)

1. The raw material mixture for the manufacture of building ceramic products containing silica and aluminum-containing components, characterized in that to provide increased compressive strength up to 130-160 MPa, it includes natural sand as a silica-containing component, blast-furnace and / or steel-making component as an aluminum-containing component slag, and the SiO2 content in the mixture is 70-85% in the following ratio of components, wt.%:
natural sand 60-80 blast furnace slag 0-40 steelmaking slag 0-40 soluble glass 0-5 2. A method of manufacturing building ceramic products from a raw mix according to claim 1, comprising preparing a raw mix, molding products and firing, characterized in that the raw mix is co-milled before dispersion to 20-50 microns, pressing is carried out at a pressure of 35-150 MPa , firing is carried out according to the following mode: raising the temperature to 500 ° C at a speed of 150-200 ° C / h, then to 1050-1150 ° C at a speed of 65-150 ° C / h, holding at 1150 ° C - 1-2 hours cooling at a speed of 100-150 ° C / h.