RU2231505C1 - Ceramic mass for making wall and facing articles - Google Patents

Abstract

FIELD: building materials.

SUBSTANCE: invention relates to wall and facing ceramics and can be used in manufacturing heat-insulating and decorative materials. Ceramic mass for making wall and facing articles comprises the following components, wt.-%: clay, 40-95; foam glass grits, 5-60; sulfite-yeast dried mash, above 100% of dried mixture, 0.3-0.5. The composition provides reducing heat conductivity, diminishing drying and firing shrinkage and reducing density of wall and ceramic articles also in retaining and enhancing their strength.

EFFECT: improved and valuable properties of mass.

3 tbl, 2 ex

Description

The invention relates to wall and facing ceramics and can be used in the production of heat-insulating and decorative materials - tiles, blocks, wall panels, etc.

Known mass for the manufacture of ceramic products, including fusible and refractory clay, quartz sand and cullet as smooths [1].

On the basis of the known mixture ceramic products are obtained by casting, molding, pressing and subsequent firing at a temperature of 1000 ... 1100 ° C. The resulting ceramic products have compressive strength up to 15 MPa and a wide sintering range of 80 ... 100 ° C.

Along with the indicated advantages, there are also significant disadvantages that significantly worsen the technological and operational qualities of the products obtained, in particular:

1) a high coefficient of thermal conductivity (0.90 ... 0.94 W / m · K), which leads to an increase in the consumption of building materials in construction;

2) large shrinkage during the drying and firing of ceramic products (20.5 ... 27.0 vol.%), This makes it difficult to obtain materials with specified geometric parameters;

3) high density (1840 ... 1960 kg / m ³ ), which requires an increase in the cost of materials at the manufacturing stage and, as a consequence, makes the mass of wall structures heavier.

The closest ceramic mass in comparison with the claimed is a ceramic mass [2], which includes the following components, wt.%: Refractory clay 20 ... 90; low-melting clay 1.2 ... 62.0; skull (ground battle of products) 0.5 ... 2.0; cullet 2.5 ... 3.6; low-calcium brown coal ash 0.3 ... 10.5; expanded vermiculite sand with a particle size of not more than 2.5 mm 3.0 ... 4.4; sulphite-yeast mash (dry) in excess of 100% dry mix - 0.3 ... 0.5.

From a mixture of known composition receive facing ceramic materials with improved decorative characteristics. The introduction into the composition of the raw material mixture of expanded vermiculite sand and low-calcium lignite ash allows to slightly reduce the density of products (up to 1620 ... 1680 kg / m ³ ) and their thermal conductivity (up to 0.78 ... 0.82 W / m · K) ; the introduction of the skull (ground battle of products) also reduces shrinkage during drying and firing (up to 18.2 ... 21.4 vol.%). In the known mixture, vermiculite sand, low-calcium brown ash and skull (ground battle of products) are thinning materials, and cullet is smooth.

Along with these advantages, there are significant disadvantages. The disadvantages of the prototype are the high coefficient of thermal conductivity, high shrinkage during drying and firing, the increased density of the resulting wall ceramic products.

The present invention solves the problem of reducing thermal conductivity, reducing shrinkage during drying and firing, as well as reducing the density of wall ceramic products while maintaining and increasing strength.

To achieve this goal, the ceramic mass for wall and facing products, including clay, thinning components, melt and dry yeast mash, according to the proposed solution, contains fine foamed glass with a grain size of 0.1 ... 2.5 mm for thinning components and melt. the following ratio of components, wt.%:

clay 40 ... 95

foam glass grit 5 ... 60

sulphite-yeast mash (dry) in excess of 100% dry mix 0.3 ... 0.5

Characterization of mass components

1. Refractory clay of the Lukoshkinskoye field. TU 21-4434-84. Refractoriness 1430 ... 1570 ° С. Plasticity 9 ... 12. The color after firing is red. The chemical composition of loam in the Tula region. presented in table. 1.

2. Fusible clay (loam) of the Tula region. Refractoriness 1200 ... 1230 ° С. Plasticity 17. The color after firing is light red. The chemical composition of the clay Lukoshkinskoye deposits are given in table. 1.

3. Foam glass according to TU 5914-003-02066339-98 "Heat-insulating materials and products", produced in BSTU. The initial foam glass with a density of 150 ... 200 kg / m ^{3 was} crushed in a jaw crusher and sieved through a sieve with a hole diameter of 2.5 mm. The residue on the sieve was crushed and again additionally sieved on a sieve with a hole diameter of 2.5 mm. To remove dust fractions, crushed foamglass passing through a 2.5 mm sieve was placed on a sieve with a mesh size of 0.1 mm and vibrated until the dust spill stopped. Thus, in the inventive composition of the raw material mixture used foamed glass grits with a size of 0.1 ... 2.5 mm and a bulk density of 260 kg / m ³ . For the preparation of grains, you can use trimming and battle blocks of foam glass. The chemical composition of the foam glass is given in table. 1.

4. Sulphite-yeast mash (SDB). Adopted as a plasticizer in order to increase the strength of pressed semi-finished products and increase crack resistance during drying and pressing according to TU 81-04-546-79. SDB was introduced with mixing water in the form of an aqueous solution of 3 and 5% concentration.

Under industrial conditions, the composition of the ceramic mass in the form of a press powder is prepared in a known manner. For example, finely ground dry clay raw materials are dosed, sifted through a sieve with a mesh diameter of not more than 1 mm, foam glass grains are added in the ratio by dry weight indicated in the table. 2. A mixture of dry components is moistened with a 5% SDB solution to a moisture content of 6 ... 10%, similarly to [2], mixed until homogeneous. The mixture is formed by semi-dry pressing under pressure.

Products are dried to a residual moisture content of 0.5 ... 2%, similarly to [2], and then fired at a temperature of 900 ... 950 ° C.

Example 1. Weighed previously dried crushed and sieved through a sieve with a hole size of 1 mm Lukoshkinsky clay in the amount of 6.0 kg (table. 2, mixture 1), 4.0 kg of crushed foam glass sifted through a sieve with a diameter size was added to this clay cells of 2.5 mm and 0.1 mm remaining on the sieve.

These two components were mixed in a laboratory screw mixer and at the same time a 5% aqueous solution of SDB in the amount of 1 kg (0.5% SDB in excess of 100% dry mix) was fed while mixing. Semi-dry mass was formed by pressing on a hydraulic press under a specific pressure of 10 MPa.

The formed samples in the form of tiles with a size of 192 × 142 × 9 mm and cylinders with a diameter and height of 50 mm (the last samples were intended to determine the compressive strength) were dried to a residual moisture content of 2%, and then fired at a maximum temperature of 950 ° C with exposure 2 hours, i.e. The production conditions for building red brick were modeled. After cooling, material samples were tested for strength, water absorption, thermal conductivity; the density and shrinkage value were determined during drying and firing. The decorative properties of the samples were visually determined. The test results are given in table. 3 (mixture 1).

Example 2. Weighed pre-dried crushed and sifted through a sieve with a hole size of 1 mm Tula loam in the amount of 6.0 kg (Table 2, mixture 3), 4.0 kg of crushed foam glass sifted through a sieve with a diameter size was added to this loam cells of 2.5 mm and 0.1 mm remaining on the sieve.

These two components were mixed in a laboratory screw mixer and at the same time a 5% aqueous solution of SDB in the amount of 1 kg (0.5% in excess of 100% dry mixture) was fed while mixing. Semi-dry mass was formed by pressing on a hydraulic press under a specific pressure of 10 MPa.

The formed samples in the form of tiles with a size of 192 × 142 × 9 mm and cylinders with a diameter and height of 50 mm were dried to a residual moisture content of 2%, and then fired at a maximum temperature of 900 ° C for 2 hours. After cooling, material samples were tested for strength, water absorption, thermal conductivity; the density and shrinkage value were determined during drying and firing. The decorative properties of the samples were visually determined. The test results are given in table. 3 (mixture 3).

The ratios of the raw components and the firing temperature of the ceramic masses in examples 1 and 2 (Table 1, mixtures 1-3) were selected from the experimental series of samples as the most rational in terms of microstructure and physicomechanical properties of the obtained wall ceramic products.

In a similar way, all other mixtures of the proposed ceramic mass were prepared and all, respectively, on its basis samples of wall materials and tiles, including grains of foam glass exceeding the grain size, compositions 8-9, as well as the known mass composition 10 (prototype), Results properties are given in table. 3. The experiments were carried out in laboratory conditions BSTU.

Data analysis table. 3 test results of the properties of samples of wall and facing ceramics made from the compositions of the proposed mass, shows the following:

1. All mixtures 1-7 meet the requirements of GOST 7025-91 "Brick and ceramic and silicate stones".

2. Introduction to the composition of the claimed mass of grains of foam glass as a thinner component and flux allows you to get high-quality ceramic materials.

3. With a decrease in the dose of foamed glass grains, the thermal conductivity coefficient, density, and the total shrinkage during drying and firing slightly decrease compared to the prototype, but the strength of the samples significantly (by 2–3 times) (mixtures 5 and 6). A further decrease in the dose of foamed glass grains is impractical, because the resulting ceramic materials slightly exceed the quality characteristics of the prototype.

4. With an increase in the dose of foamed glass grains, the density, thermal conductivity and shrinkage of ceramic materials decrease, however, their strength decreases due to an increase in the friability of the structural skeleton (mixture 7), a further increase in the dose of grains in the mass is impractical because there is a decrease in the strength of the obtained ceramic materials due to the appearance of melts.

5. The use of foamed glass pellets with a particle size of less than 0.1 mm does not allow to obtain ceramic products of low density and with a reduced coefficient of thermal conductivity, because dusty particles of foam glass do not contribute to the creation of a porous structure of ceramic materials (mixture 8).

6. The use of foamed glass with a particle size of more than 2.5 mm is also impractical, because the resulting system of large pores contributes to the occurrence of convective heat transfer in them, which reduces the thermal insulation characteristics of the materials obtained (mixture 9), when firing such a mass, serious structural defects, friability, and melts, which reduce the strength characteristics, worsen the appearance of the products.

The inventive composition of the ceramic mass in comparison with the prototype has the following advantages:

1) thermal insulation properties are more than doubled;

2) the density while maintaining the required physical and mechanical characteristics and the amount of water absorption (10 ... 12%) is reduced by 30%;

3) ceramic masses during drying and firing have minimal shrinkage.

The physicochemical nature of the technical solution to achieve this is as follows: foam glass due to low bulk density (400 ... 450 kg / m ³ ), occupying the volume of the raw material mass, forms the porous structure of the raw material, and the total surface of these particles is high due to the developed surface and therefore, the conditions for interaction with clay particles are very effective. During firing, the foam glass goes into the liquid phase, actively interacting with clay particles over the entire surface of the pore. By this time, the clay component of the mass creates a strong structural skeleton of the material, which prevents the thermal shrinkage of the product. In the process of isothermal exposure at a maximum temperature for 1.5 ... 2 hours, the finished glass phase leads to an acceleration of mullite formation reactions with subsequent crystallization of mullite on the pore walls and their reinforcement (proved by microscopic and petrographic studies). Reinforcement, high density of pore walls prevent crack formation of the obtained glass-ceramic materials, this explains their high strength and low water absorption (10 ... 12%). Ensuring uniform closed porosity in the ceramic material leads to a decrease in the thermal conductivity coefficient by almost half compared with the prototype.

Traditional methods for reducing the density of ceramic products involve the use of burnable additives (wood flour, sawdust). In such products there is a significant amount of microcracks and weak contacts in the places of pore formation, which leads to low strength and high water absorption.

The authors first discovered the unknown behavior of foamed glass grains in combination with refractory and low-melting clays and SDB in the claimed amounts, consisting in the porosity and hardening of the macrostructure of the sintered mass, which makes it possible to obtain building materials with a reduced density without reducing the strength characteristics.

It was impossible to predict the behavior of foamed glass pellets when used in combination with refractory and low-melting clays and SDB in the claimed quantitative proportions and sizes of the pellets at the filing date of the application, because It is well known that grains are a low-melting component, causing compaction and, as a consequence, weighting of the ceramic mass.

The resulting wall and cladding products have good decorative indicators - they look like natural tuff materials, and products from white-burning clay are shell rock. To achieve a greater decorative effect, an additional introduction of pigments into the composition of the raw ceramic material is allowed.

The use of the inventive ceramic mass in the building materials industry will also solve the problem of recycling a significant part of the waste foam.

Literature

1. Auth. testimonial. No. 814964, 1981.

2. RF patent No. 2099307, 1997.

Claims (1)

Ceramic mass for wall and facing products, including clay, thinning components, melt and dry yeast mash, characterized in that as thinning components and smoothing contains foam glass grains with a grain size of 0.1-2.5 mm in the following ratio, wt .%: Clay 40-95 Foam of glass foam 5-60 Dry sulphite yeast mash over 100% dry mix 0.3-0.5