RU2748199C1 - Raw mixture for production of building ceramic products - Google Patents

Abstract

FIELD: building materials.

SUBSTANCE: invention relates to the production of clinker and facing bricks and stones by the method of semi-dry molding. The raw mixture contains components in the following ratio, wt. %: low-melting clay - 25-29, ash-and-slag mixture - 15-20, chamotte-kaolin dust - 35-45, crushed burnt rocks - 15-25.

EFFECT: increased strength and frost resistance of ceramic products.

3 cl, 3 dwg, 4 tbl

Description

The invention relates to building materials and can be used for the production of building ceramics, mainly clinker and facing bricks and stone by the method of semi-dry molding.

State of the art.

Known raw mixtures for the manufacture of building ceramic products contain clay plastic raw materials and man-made waste, which are used in different quantities, in wt%, products of combustion of solid carbon-containing raw materials, such as: burnt rocks -30-50 (RU 2483042, IPC С04В 33/135 publ. 27.05.2013) [1], shale ash - 30-50 (RU 2555170, IPC С04В 33/132 publ. 10.07.2015) [2], heap "red"-10-64; black heap - 10-64 (RU 2568458, IPC С04В 33/138 publ. 20.11.2015) [3], burnt rocks -25-38 (RU 2593284, IPC С04В 33/135; С04В 33/132 publ. 10.08 . 2016) [4], TPP ash - 50-60 and carbon black -0.5-2.0 (RU 2532933, IPC С04В 33/135, publ. 20.11.2014) [5], ash from coal combustion -20 -90 (RU 2387617, IPC С04В 33/135, publ. 04/27/2010) [6]. Ceramic mass (RU 2496742, IPC С04В 33/135 publ. 10/27/2013) [7] contains low-melting clay and technogenic waste with a particle size of less than 0.315 mm, consisting of fly ash from TPP - 80 wt.% And dust entrainment from alumina calcination furnaces - 20 wt.%, With the ratio SiO ₂ : Al ₂ O ₃ = 1: 1, with the following ratio of components, wt.%: Low-melting clay - 85-90; the specified man-made waste - 10-15. Bricks made from these raw materials by dry molding have a maximum compressive strength of 47.1 MPa.

The known solution makes it possible to use the resulting mixtures of burnt and unburned rocks at the stated ratio for the production of ceramic bricks and ceramic stones by semi-dry pressing, and also to reduce their density. As a result, a compressive strength of 19.2 MPa was obtained for the finished product, frost resistance of 75 cycles, density of 1380 kg / m ³ , water absorption of more than 6, which is typical for ordinary bricks.

As follows from the prior art, the difference in the compositions of the used technogenic raw materials affects the physicochemical processes during mixing, molding and sintering of the raw materials and, consequently, the physical and mechanical characteristics of the finished product, which include mechanical compressive strength, frost resistance, water absorption , density. The difficulty in achieving high values of the physical and mechanical indicators of the quality of ceramic products lies in the choice of charge components that provide for a given concentration of joint interaction, in which, during molding and firing, the structure of a ceramic shard is formed and the required amount of minerals is formed, providing high strength and frost resistance of products with a low content of low-melting clay.

Brief description of the invention

The objective of the present invention is to develop a raw mixture for the manufacture of building ceramic products of grades 500 and 600, which have high values of physical and mechanical quality indicators, namely, values of mechanical compressive strength of 52.8-64.5 MPa and frost resistance of 300 cycles.

The present invention relates to the composition of the raw material mixture for the manufacture of building ceramic products, which contains low-melting clay and, as man-made waste, ash and slag mixture, chamotte-kaolin dust and burned-out rocks with the following ratio of initial components, wt. %: low-melting clay 29-25, ash-and-slag mixture 15-20, fireclay-coaline dust 35-45, crushed burnt rocks 15-25.

In a preferred embodiment:

- the particle size of crushed burnt rock is no more than 2 mm;

- the particle size of the ash and slag mixture is no more than 2 mm.

The claimed qualitative and quantitative composition of the components of the raw mixture provides a joint interaction, in which, during molding and firing, the structure of a ceramic shard is formed and the required amount of minerals is formed, affecting the increase in the strength and frost resistance of products with a low content of low-melting clay.

The present invention is illustrated by tables and photographs of the microstructure of a ceramic shard, where:

Table 1. Chemical composition of raw materials.

Table 2. Compositions of the raw mixture.

Table 3. Physical and mechanical indicators of the quality of ceramic bricks obtained from the raw mixture according to the present invention.

Table 4. Comparison of technical characteristics of ceramic products from known raw mixes and products according to the present invention.

FIG. 1. Photo of the microstructure of a ceramic shard from the raw mixture according to the claimed invention: magnification - 220 x; resolution - 400 µm.

FIG. 2. Photo of the microstructure of a ceramic shard from the raw mixture according to the claimed invention magnification: magnification - 1000 x; resolution - 50 µm.

FIG. 3. Photo of the crushing and screening complex for the processing of burnt rock from the waste dump of mine No. 26, Gukovo, Rostov region.

Detailed description of the invention.

Characteristics of the initial ingredients that make up the claimed raw mix for the manufacture of ceramic building products:

Low-melting clay is represented by a hydromica component with a minor admixture of kaolinite and montmorillonite. The dusty fraction is represented mainly by silica, calcium carbonate, iron oxides, and the sandy fraction is represented by quartz. According to the degree of plasticity, this clay belongs to the group of medium plastic, the number of plasticity is 23.0-26.2%, according to the sensitivity to drying - to the group of highly sensitive clay raw materials. Low-melting clay in the composition of the raw mix is introduced as a binder of non-plastic materials.

Ash and slag mixture is a product of coal combustion in boiler furnaces at temperatures above 1000 ° C, up to 1700 ° C. The ash and slag mixture contains up to 30% fly ash with a specific surface area of 300-350 m ² / kg. Burnt rocks are a product of long-term self-burning of inter-coal rocks associated with coal mining, stored on the surface in dumps. Self-firing of rocks in ovals occurs relatively evenly at temperatures above 1000 ° C and lasts for several years.

Burned rocks and ash-and-slag mixtures are inherently non-plastic materials. The chemical composition of the starting ingredients is shown in table. one.

Table 1. Chemical composition of raw materials

Type of raw material Mass fraction of components, wt% SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO TiO ₂ P ₂ O ₅ ∑ (K ₂ O,
Na ₂ O) SO ₃
total p.p. Low-melting clay 57.88 12.35 4.42 8.48 1.94 0.16 0.37 3.44 0.21 10.14 Ash-slag mixture 53.96 21.73 8.30 3.72 2.08 0.55 0.25 3.51 0.77 5.13 Burnt rock 54.77 22.18 7.21 1.16 1.47 0.78 0.33 3.85 1.73 4.92

LOI - loss on ignition

In terms of chemical, granulometric and phase-mineralogical composition, these wastes are largely identical to natural mineral raw materials.

In the composition of the raw material charge for facing ceramic bricks and stones, ash and slag mixture and burnt rocks play the role of a lean additive and micro-filler, improve the granulometric composition of the charge, and reduce the sensitivity of clay raw materials to drying.

The presence of spherical particles in the grain composition of the ash-and-slag mixture creates a plasticizing effect that improves the molding of products.

Burned rocks and ash-and-slag mixtures contain metakaolinite, reactive modifications of silica, alumina, iron oxides arising during firing in dumps or boiler furnaces. The presence of these active components contributes to the formation of strong contacts, the formation of a spatial structural frame of the composition during drying, which turns into a homogeneous structure of a ceramic shard during firing.

Chamotte-kaolin dust is formed during the burning of kaolin to obtain chamotte. The grain size is 15-180 microns. The content of silicon dioxide mass. %: 49-55; aluminum oxide 40-42; iron oxide 0.4-2.5. The phase composition of fine chamotte-kaolin dust is dominated by kaolinite, metakaolinite, silica, glass - 78-86%, mullite - 7-12%; corundum -7-9%. This component in the composition of the charge is a lean additive and a carrier of alumina and glass phase. The presence of a glass phase in chamotte improves the sinterability of the charge and lowers the firing temperature of the products.

This is confirmed by the high indicators of the physical and mechanical properties of ceramic masses and images of the microstructure of a ceramic shard. The photographs (Fig. 1 and Fig. 2) show samples of a sintered ceramic shard of a homogeneous structure. Of the crystalline phases in the ceramic structure, quartz, anorthite, mullite, and wollastonite have been identified. The increased amount of glass phase allows us to conclude that the formation of a dense ceramic shard is completed.

An example of a specific implementation.

The manufacture of ceramic products is carried out as follows. Burnt rocks of the mine dump and slag of the ash-and-slag mixture are subjected to crushing, grinding and fractionation to fractions of no more than 2 mm, which ensures a dense and compact packing of particles in the raw mixture. The moisture content of the lean additives is 2-3%. Crushing, crushing and fractionation of the burnt rock is carried out on the crushing production line directly at the mine dump, as shown in Fig. 3.

All components of the raw mix are mixed in accordance with the recipe and moistened to a moisture content of 7-9%.

Semi-dry molding of samples is carried out at a specific pressure of 30-35 MPa. The maximum firing temperature of samples is 970-1100 ° C. Exposure at maximum temperature is 1.5 hours.

As shown in table 2, the prepared compositions of the raw mixture 2, 3, 4 represent the content of the starting ingredients in the claimed range, the content of the starting components, and the compositions 1, 5 represent the outside of the claimed range.

Table 2. Compositions of raw mix

Components Compositions one 2 3 four five Low-melting clay 26 twenty 22.5 25 nineteen Ash and slag mixture fourteen twenty 17.5 fifteen 21 Fireclay kaolin dust 46 35 40 45 34 Burnt rocks fourteen 25 twenty fifteen 26

The structural and mechanical properties of ceramic bricks begin to form in the process of compaction of the raw mix and are fixed during firing. A ceramic brick model can be represented as a multicomponent composition consisting of clay and emaciated ingredients. The dispersed reinforcing component is quartz grains that form the quartz strengthening skeleton of the composition. The source of quartz grains is burnt rocks and ash and slag mixture. Clay is a technological bond at the stage of formation of coagulation structures during pressing and condensation-crystallization ceramic shards during firing.

A significant influence on the physical and mechanical properties of the ceramic material is influenced by the granulometric composition of quartz-containing wastes included in the composition of the raw mixture. The formation of the structure of the raw mix begins when the components are compacted under pressure. The grains of the largest fraction form the skeleton of the composition, the voids of which are filled by the next fraction, i.e. fine grains, including fly ash and chamotte-kaolin dust, fill the voids between the coarser grains. Fly ash of a zooslag mixture with a spherical shape of particles as a plasticizer facilitates the movement of grains and their contact. When the structure is compacted by applying pressure, the contact surface between the grains of the composition increases. Moisture in the form of a clay colloidal suspension is squeezed onto the surface of the contacting particles (coating effect), cementing them. As noted above, the composition of burnt rocks and ash-and-slag mixture, due to their formation, contains reactive components. When assessing the activity of these materials, they are classified as highly active additives. This provides the effect of physical and chemical contact between the grains. Such contact in the frame is much stronger than the usual mechanical interaction.

At the last stage of pressing, the structure is maximally compacted due to the further development of contact surfaces. The structure is consolidated and the ceramic shard is formed during firing. In this case, the presence of a glass phase is of great importance. The source of the latter in the composition of the raw material mixture is low-melting clay, aluminosilicate glass of the ash-and-slag mixture, chamotte-kaolin dust and partially the presence of alkaline earth and alkaline oxides of burnt rocks. An increase in the glass phase and the appearance of low-melting eutectics intensify the sintering of the charge. The quartz skeleton is involved in the sintering process due to the formation of reactive interlayers on the grain surface. Under the influence of surface tension forces, the particles converge and the material compresses. The sintering mechanism takes place as a liquid-solid phase. The liquid phase dissolves particles of solid phases and new crystalline phases crystallize from the melt. During firing, new compounds are formed based on the components of the raw mixture, and the ceramic mass acquires the properties of a stone-like material.

The greatest indicators of strength, frost resistance of a ceramic shard are associated with the presence of mullite, anorthite. Dehydrated clay minerals in the form of metakaolinite are present in the composition of burnt rocks and ash-slag mixture and chamotte-kaolin dust. During firing, metakaolinite decomposes into highly active oxides Al ₂ O ₃ and SiO ₂ , which contributes to the formation of an increased amount of mullite and anorthite. Mullite, as a mineral synthesized during firing (in dumps or boilers), is also present in the composition of the original burnt rocks and ash-and-slag mixture. Mullite also contains chamotte-kaolin dust. In addition, chamotte-kaolin dust is a carrier of an additional amount of Al ₂ O ₃ for the formation of anorthite. The presence of these minerals (mullite and anorthite) significantly increases the mechanical strength and frost resistance of ceramic bricks. In addition, the wollastonite, which is present in the original non-plastic materials of the mixture and formed during firing, reduces volumetric changes, internal stresses and shrinkage of the ceramic shard.

The introduction of complex additives to clay intensifies the sintering of the charge due to the appearance of low-melting eutectics and an increase in the glassy phase. The selected composition of lean additives helps to reduce the volumetric changes in the composition and the stability of the forming structure of the composition at all stages of the technological process. Samples from the compositions of the ceramic mass of the proposed technical solution have a sintered ceramic shard of a homogeneous structure. As a result of the joint interaction of the charge components during molding and firing, the structure of a ceramic shard is formed and the required amount of minerals is formed, providing high strength and frost resistance of products with a low content of low-melting clay. This is confirmed by high indicators of physical and mechanical properties of ceramic masses and photographs of the microstructure of a ceramic shard. In FIG. 1 and FIG. 2 shows photographs of the microstructure of a sintered ceramic shard, which indicate the homogeneity of the structure obtained. Of the crystalline phases in the ceramic structure, quartz, anorthite, mullite, and wollastonite have been identified. The increased amount of glass phase allows us to conclude that the formation of a dense ceramic shard is completed. Table 3 shows the physical and mechanical characteristics of the quality of ceramic bricks obtained from the raw mixture according to the present invention. Measurement of mechanical strength in compression, MPa, mechanical strength in bending, in MPa, frost resistance, in cycles, water absorption, in% was carried out according to the methods described in GOST [8-10].

As follows from the table. 3, a ceramic product obtained from the claimed composition of the raw mixture (compositions 2, 3, 5) has high values of compressive strength, bending strength, frost resistance, low water absorption, which ensures the manufacture of building ceramic products of grades 500 and 600, clinker bricks, stone.

Within the limits of the claimed ratios of the ingredients of the raw mixture, the highest strength values of 52.8-64.5 MPa, frost resistance of 300 cycles and low water absorption values of 2.97-3.87 are achieved, which corresponds to GOST [8].

Table 3. Physical and mechanical indicators of the quality of ceramic bricks obtained from the raw mixture according to the present invention.

Indicators Indicator values for formulations one 2 3 four five Compressive strength, in MPa 41.4 52.8 57.7 64.5 36.4 Flexural strength, in MPa 3.85 5.53 5.85 6.25 3.25 Frost resistance, cycles 200 300 300 300 175 Water absorption, in% 6.13 3.87 3.29 2.97 7.49

Table 4 shows a comparison of the physical and mechanical indicators of the quality of known ceramic products and ceramic bricks obtained from the raw mixture according to the present invention.

Table. 4. Comparison of physical and mechanical parameters of the quality of known ceramic products and ceramic bricks obtained from the raw mixture according to the present invention.

Name
indicator RU 2496742 RU 2568458 RU 2555170 RU 2593284 Product of the present invention Compressive strength, MPa 19.2 19.2 19.8 19.8 64.5 Bending strength, in MPa _ _ _ _ 6, 25 Frost resistance, in cycles 94 70 99 107 300 Water absorption, in% 18.3 2.97 Density, in kg / m ³ 1380 1180 1830

As follows from table 4, the use of the inventive raw mixture provides high quality indicators of ceramic building products, which are not achieved by the known compositions of the raw mixture from the prior art. In addition, in the proposed raw mixture, 75% of the composition is made up of ingredients from technogenic raw materials. The use of waste in the composition of the raw mixture for the production of ceramic products makes it possible to reduce the negative impact of technogenic raw materials on the environment and to reduce the cost of production, since materials from technogenic raw materials are 25-35% cheaper than natural materials, and to expand the raw material base for ceramic materials. The invention has been mastered on an industrial scale.

Information sources:

1. RU 2483042, IPC С04В 33/135 publ. 27.05. 2013.

2. RU 2555170, IPC С04В 33/132 publ. 10.07. 2015.

3. RU 2568458, IPC С04В 33/138 publ. 20.11.2015.

4. RU 2593284, IPC С04В 33/135; С04В 33/132 publ. 10.08. 2016.

5. RU 2532933, IPC С04В 33/135, publ. 20.11.2014.

6. RU 2387617, IPC С04В 33/135, publ. 04/27/2010.

7. RU 2496742, IPC С04В 33/135 publ. 10/27/2013.

8. GOST 530-2012. Ceramic bricks and stones. General technical conditions. Date of introduction 2013-07-01.

9.GOST 8462-85. Wall materials. Methods for determining ultimate strength in compression and bending. Date of introduction 1985-07-01

10. GOST 7025-91. Ceramic and silicate bricks and stones. Methods for determining water absorption, density and frost resistance control. Date of introduction 1991-07-01

Authors:

Buravchuk Nina Ivanovna

Guryanova Olga Vladlenovna

Claims (3)

1. Raw material mixture for the manufacture of building ceramic products, containing low-melting clay and as man-made waste ash and slag mixture, chamotte-kaolin dust and burnt rocks with the following ratio of initial components, wt. %: low-melting clay 25-29, ash-and-slag mixture 15-20, chamotte-kaolin dust 35-45, crushed burnt rocks 15-25. 2. Raw mixture according to claim 1, characterized in that the particle size of the burnt rock is no more than 2 mm. 3. Raw mixture according to claim 1, characterized in that the particle size of the ash and slag mixture is no more than 2 mm.

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