8.4. Glass-ceramic materials

Pyrocerams, slagcerams and stone casting belong to glass-ceramic materials. The general feature of these materials is a presence of both crystalline and glass phases in their structure, which provides high mechanical properties, thermal and anticorrosive resistance, low wearability etc. Glass-ceramic materials are applied for production of proof to the abrasion revetments, responsible parts of structures and others like that. Glass-ceramic pipes use for manufacture of heat exchangers. Due to ability of some glass-ceramic materials to take in slow neutrons and heat resistance they are applied in production of bars of nuclear reactors and for biological protection.

Pyrocerams are products of crystallization of glasses. The process of production of pyrocerams includes the manufacturing of glass of certain composition, forming products from it and special heat treatment. There are technical pyrocerams and slagcerams.

Slagcerams are widely used in construction. Slags of ferrous and non-ferrous metallurgy, and also ash from incineration of anthracite coal are the raw material materials for slagcerams. The production of slagcerams consists in slag glasses melting, forming products from them and their following crystallization. A batch for the making of glasses consists of slag, sand, alkaline and other admixtures. The most effective is the use of molten metallurgical slags that saves to 30…40% amounts of heat, which is outlaid on melting.

Slagcerams as sheets, pressed flags, pipes and other products are manufactured at the plants. Formed products are supplied to crystallizer, where the certain mode of thermal treatment is automatically supported.

Slagcerams differs from the number of construction materials with higher physical and mechanical properties. Due to high strength they approach to cast-iron and steel, though in three times lighter than them (Table 8.4). The heat-resistance of slagcerams is 150...200°C. Indexes of chemical resistance and resistance to abrasion are especially high. Slagcerams can be processed by the different methods: grinding, polishing and cutting.

Basements and facades of buildings are faced by the flags of facial slagceram, also internal walls and partitions, balconies are decorated. Slagceram is an effective material for the stairs, window-sills and other structural elements of buildings. It is applied also for protection of building constructions and apparatus in chemical, mining industry and other industries.

Stone and slag casting is stone product, obtained by melting of igneous or sedimentary rocks and slags, pouring of fusion in forms and heat treatment of products with the purpose of passing of crystallization and destressing.

For the making of stone poured products fusible rocks are used as rule - basalt, diabase and others like that. In the batch admixtures which reduce the temperature of melting and increase ability to crystallization (fluor-spar, dolomite, chromite etc.) are entered.

Table 8.4

Properties of pyrocerams and other construction materials

Index	Pyroceram	Slagceram	Rock glass-ceramic	Window-pane	Granite	Steel
Bulk density, kg/m3	2600… 2900	2600… 2800	2900… 3000	2500… 2600	2600… 2800	7800
Ultimate strength, MPa:
at a compression	800…1000	500…650	700…850	600…700	100…250	420…550
at a bend	100…225	90…130	130…170	60…70	10…15	400…1600
Modulus of elasticity, Е 103, MPa	72…135	90…100	40…50	60…70	8…25	210…220
Acid resistance, %	97,8…98,9	98,8…99,8	99,8	55…58	95…95,5	–
Alkali-resistance, %	–	90…94,7	94…96	98,9	–	–
Wearability, g/cm2	–	0,01	–	0,5…0,6	–	–

Stone poured products are exceeded than natural stone and row of other materials due the density, firmness to the chemical action, resistance to wearing and other properties. Wearing of products from a stone casting in 3...5 times less than granite, basalt or diabase, and equals 0.016...0.1 g/cm², and ultimate compressive strength is 200...400 MPa.

The basic types of stone poured products are flags, pipes and other details, intended for work in severe climatic and other operating terms.

Various products are poured from molten metallurgical slags: stone for roads and floors of industrial buildings, tubing, kerb-stones, anticorroding tiles, pipes etc. The poured products from slag fusion are more economic advantageous, than stone casting, approaching them by mechanical properties. The bulk density of the poured products from slag equals 3000 kg/m³, and ultimate compressive strength is 500 MPa.

Due to wear resistance, heat-resistance and a series of other properties the slag casting exceeds the reinforced concrete and steel. The poured products from a slag are more effective than steel in different linings, for example hoppers for transporting of abrasive materials (ores, agglomerates, crushed stones, sand and etc). Their service life is in 5...6 times longer than steel linings.

The poured paving stones for roads and floors of industrial buildings are not less effective. Service life of highways from a slag poured paving stones between major repairs is twice greater, and performance is cheaper, than asphalt one. Tubings, heat-resistant blocks, chemically proof products are poured from a slag.

Slag products for the decline of internal tensions are reinforced with steel reinforcement. Steel reinforcement prevents cracks formation. Reinforced slag products can be used in place of the precast reinforced concrete, because they have higher strength. However the lack of these products is some decline of strength of steel at the high temperature of slag fusion, and also comparatively high labour intensiveness of production.

For production of the porous slag casting pore-formation of slag fusion is executed. The products of various configurations are formed from porous slag fusion. Depending on the degree of pore-formation the bulk density of poured products is 350...1500 kg/m³, ultimate compressive strength is equal to 1.5...30 MPa.