Basic types of ceramic materials

Masonry materials. Masonry materials are the most considerable for construction among ceramic products. They can be divided by the type of products at bricks, blocks and panels; by destination - at ordinary (for building of external and internal walls) and facing (for facing of walls); by the method of manufacture - on the products of the soft-mud and dry pressing; by heat engineering properties and density - at effective ceramics with average density <1400 kg/m³; conditionally effective - with average density equals 1400-1600 kg/m³ and ordinary - with average density ³1600 kg/m³.

A ceramic brick (Fig.7.7) has a form of rectangular parallelepiped and different standard sizes (Table 7.3).

Standard sizes of brick

Bricks may also be classified as solid (less than 25% perforations by volume, although the brick may be "frogged," having indentations on one of the longer faces), perforated (containing a pattern of small holes through the brick removing no more than 25% of the volume), cellular (containing a pattern of holes removing more than 20% of the volume, but closed on one face), or hollow (containing a pattern of large holes removing more than 25% of the brick's volume).

Blocks may be solid, cellular or hollow. Blocks have a much greater range of sizes. Standard coordinating sizes in length and height (in mm) include 400×200, 450×150, 450×200, 450×225, 450×300, 600×150, 600×200, and 600×225; depths (work size, mm) include 60, 75, 90, 100, 115, 140, 150, 190, 200, 225, and 250.

The minimal compressive strength of bricks and blocks produced in the USA and European Union is about 7 MPa. Strength can be changed according to the field of application. Usually, in England common house brick has the strength in a range of 20–40 MPa.

House walls from the solid brick with density 1700-1900 kg/m³, as a rule, have a thickness up to 2.5 bricks. If apply the hollow bricks with density 1300-1450 kg/m³, thickness of wall is diminished on half-brick, weight on 35%, consumption of mortar on 45%. At application of ceramic blocks, consumptions of materials and labour are diminished at 20-30% comparatively with an ordinary ceramic brick.

Water absorption of solid bricks should be no less than 8%, hollow bricks no less than 6%. Frost-resistance of common house brick in the saturated water state can be in the range of 15-50 cycles of freezing and thawing.

For a bricks and blocks the row of other indexes are also standardized: size of hollows, deviation from sizes, number of the damaged corners and edges, amount of cracks, etc.

Overfired and insufficiently fired ceramics should be rejected as defective. Products, which have the lime impurities, should be also rejected due to ability of cracking at steam treatment.

Large wall blocks and panels belong to industrial ceramic masonry materials (Fig. 7.8).

Large blocks are made from a solid or hollow bricks and blocks on the special plants with filling of seams by cement-sand mortar. In order that mortar hardened quickly, blocks are steamed. Application of wall blocks enables to decrease the total labour consumption on the erection of walls, and also to reduce the construction terms. Basic defects of the of large blocks use are plenty of nominal sizes, complication of installation and increase of cement content.

Most radically the task of industrial application of ceramic bricks and blocks decides making from them at the plant of panels from which then walls are installed. By construction panels are divided on one-, multi-layered, continuous and with cuts; by purpose - for external and internal walls; by the type of loadings, what they are taken up - on bearings, self-bearings and partitions. Nominal sizes of panels are determined by the construction of building for which they are intended.

Depending on the number of floors and loading which is perceived, they are designed by thick in one, one and a half and two bricks. Panels are reinforced by the horizontal and vertical welded steel frameworks.

Labour consumption for the construction of walls from ceramic panels essentially decreases comparatively with the same at the monolithic bricking.

Ceramics for roofs and facings. Basic ceramic material for roofs is a roof tile; its main positive features are high strength and longevity. So, if the normative term of service of roll materials is 15 years, steel sheet 25, asbestos cement - 30 years, tiles - 80 years. The lacks of tile are its large weight (35-70 kg/m²), fragility, necessity in large inclination of roof. Small-size and hand method of layering of tile predetermines large labor intensiveness of arranging of tiling. Due to the increasing of issue of industrial roofing materials application of roof tiles is diminished. The variety of roof tiles (Fig.7.9) is manufactured.

- Flat tiles - the simplest type, which are laid in regular overlapping rows. An example of it is the "beaver-tail" tile. This profile is suitable for stone and wooden tiles, and most recently, solar cells.

- Imbrex and tegula, an ancient Roman pattern of curved and flat tiles that make rain channels on a roof

- Roman tiles - flat in the middle, with a concave curve at one end at a convex curve at the other, to allow interlocking.

- Pantiles - with an S-shaped profile, allowing adjacent tiles to interlock. These result in a ridged pattern resembling a ploughed field. An example of this is the "double Roman" tile, dating from the late 19th century in England and USA.

- Mission or barrel tiles are semi-cylindrical tiles made by forming clay around a curved surface, often a log or one's thigh, and laid in alternating columns of convex and concave tiles.

Roof tiles are 'hung' from the framework of a roof by fixing them with nails. The tiles are usually hung in parallel rows, with each row overlapping the row below it to exclude rainwater and to cover the nails that hold the row below.

There are also roof tiles for special positions, particularly where the planes of the several pitches meet. They include ridge, hip and valley tiles.

A roof tiles have to maintain the destructive loading 800-1400 N, its frost-resistance should be not less than 25 cycles of freezing and thawing.

Ceramic materials for facings are divided into products for facing of facades and internal facing. A face bricks and blocks, facade tiles, carpet ceramics, terracotta details belong to the products intended for facing of facades of buildings.

The most effective materials for facing of facades are face ceramic bricks and blocks, which execute the functions of masonry and facing materials at the same time. They are produced solid, perforated, cellular and hollow with the same strength as the ordinary masonry materials. White or ordinary clays are used for facing products making. Water absorption of products from white clay is 6-12%; from ordinary clay is no more than 14%. There are additional requirements in relation to homogeneity of raw material and color for the fired products.

Besides the one-layered a double-layered bricks are produced. They have facing layers in thick 3-5 mm. From white and colored clays the decorative facing surface of bricks and blocks is obtained by engobe coating or glazing. A glaze unlike engobe during a firing melts and forms a brilliant glassy layer. Engobed surface is dull.

Facade tiles depending on sizes are divided into large- and fine-size, on the methods of fixing - embedded, which are set simultaneously with construction of walls and attached, which are set on mortar after the building of walls.

Tiles are produced of many nominal sizes. The large-size tiles of square and rectangular forms can be manufactured. A facing surface of tiles can be smooth and shiny, rough or fluted, one- and multicolored, with a pattern, glazed and unglazed. The frost-resistance of tiles can achieved 50 cycles of freezing and thawing, water absorption - up to 4%.

By coordinating sizes (a coordinating size includes a total size of nominal size of tile and width of mortar seam which are 4-8 mm). Usually they can be from 50х50 mm to 300х150 mm (thickness 7 or 9 mm).

Fine-size tiles can be supplied also in carpets. In this case they are glued by a facing side on a paper. The sizes of carpets should be related to the sizes of constructions which are faced.

Tiles for internal facing are produced square (100× 100, 150×150 and 200×200 mm, etc), rectangular (150×25, 150×75, 150×100, 200×100 and 200×150 mm, etc) and shaped (for the corners of facing, cornices and plinths). Most widespread tiles are covered by transparent or opaque glaze. Tiles for internal facing are applied in dwelling houses, public-service centers and industrial buildings with large humidity or with enhanced hygiene and sanitary requirements.

Floor tile should have a high density, strength, abrasion resistance. The clays which are well sintering with admixtures of fluxing agents and pigments are used for their production.

Water absorption of the unglazed tiles should be no more than 3.5%, glazed – 4.5%, loss of weight at abrasion no more than 0.06 g/sm². Tiles for a floor by a form are square, rectangular, three -, five-, six-, octahedral and figured. A facing surface of tiles can be smooth and shiny, fluted, stamped and multicolored, figured, marble-like.

Ceramic tiles may be painted and glazed. Small mosaic tiles may be laid in various patterns. Floor tiles are usually set on mortar, consisting of sand, cement and often a latex additive for extra adhesion. The spaces between the tiles are filled with sanded or unsanded floor grout.

The unglazed, natural are painted ceramics with water absorption of 8-10% belong to terracotta. Bas-reliefs, cornices and other details of the architectural decoration are made of terracotta.

Ceramic pipes. Drain-pipes are applied for arranging of the closed drainage-systems. Drain-pipes can be cylinder, six- and octahedral forms with different internal diameters.

Drain-pipes are produced unglazed, with smooth internal surface, water absorption 12-18% and frost-resistance (if Required) not less than 15 cycles. During a test pipes should maintain hydraulic pressure not less than 0.05 MPa and destructive effort not less as 1.5-2.0 MPa.

Efficiency of drain-pipe is determined by the amount of water which is taken by it for time unit.

Unlike drain-pipes, sewage-pipes belong to the dense sintered ceramics. They are produced as hollow cylinders with a bell, with an internal diameter 125-600 mm and length 300-1200 mm. For the increase of watertightness and chemical resistance, and also diminishing of resistance flowing of liquids, sewage-pipes are covered from outside and from within by a glaze.

Basic quality indexes of sewage-pipes are following: possible external loading 2 -3·10⁴ N/m; hydraulic pressure not less than 0.2 MPa, water absorption not less than 9-11%; acid resistance not less than 90%.

Heat-resistant and acid-proof ceramics. For ordinary refractories a fire-resistance should be 1580-1770°С; high fire-resistant refractories – 1770-2000°С; the highest fire-resistance refractories - over 2000°С. Fire-resistance is measured accordingly to the softening temperature of the pyroscopes, specially made from ceramic mixture, which have a form of the three-cornered cut away pyramid, and also by optical and electric pyrometers.

Typical refractoriness are dinas, quartz and chamotte ones. They differ by a raw materials and methods of making. Dines refractories are obtained by the firing of quartz materials, as a rule, at a lime on a clay copula. Quartz refractories are made by melting of natural quartz, chamotte - by the firing of fire-clays.

Singularities of dinas refractories are a heat-resistance and low firmness against the action of most slag. They are not used for the lining of stokers; and are applied for construction of glass-work, steel-smelting, coke and other furnaces.

Among the high fire-resistant materials alumina, dolomite, chromic, carborundum refractories are applied the widest; highest fire-resistance - magnesite, chromic-magnesite, zirconium, graphite are used. Products from clean oxides and unoxygen compounds - nitrids, borids, carbides, silicides, etc have a highest fire-resistance and other valuable properties.

Ceramic refractories are made as a bricks of different forms and sizes.

For protection of building constructions and equipment which work under the conditions of acid aggressive environments, in particularly at the lining of chimneys, an acid-proof brick is used. It is made rectangular, radial and shaped from plastic refractory or heat-resistant clays of the proper chemical composition, which do not contain the impurities of gypsum, sulphuric pyrites, and carbonates.

Ceramic products are transported in containers, which provide their safety, mechanized loading and unloading.

Date: 2015-12-18; view: 1169