Stone and cast stone

Unit 6

BUILDING STONE

a)granite	b)stone cladding	c) the great Zimbabwe kingdom, the 11th century

LEAD-IN  

Figure 6.1

1 Match the terms with definitions:

1. rock	a) hard solid non-metallic mineral matter of which rock is made, especially as a building material
2. stone	b) a building component, such as a block or lintel, made from cast concrete with a facing that resembles natural stone
3. marble	c) a very hard, granular, crystalline, igneous rock consisting mainly of quartz, mica, and feldspar and often used as a building stone
4. granite	d) any natural material, hard or soft (e.g. clay), having a distinctive mineral composition
5. cast stone	e) a hard crystalline metamorphic form of limestone, typically white with coloured mottlings or streaks, which may be polished and is used in sculpture and architecture

2 Read the advertisements and in two minutes be ready to speculate on stone applications. What are other areas of stone applications?

a) Все знают, что натуральный камень очень часто используют для наружной отделки, ведь более подходящего материала для этого дела не придумаешь: природные камни, обладающие высокими коэффициентами прочности, могут прослужить вам не одну сотню лет.

b) Искусственный камень - широкие возможности для дизайнера. Он экологичен, доступен, легок, прост в монтаже, производится в близком от места строительства регионе и имеет широкую цветовую гамму, а его формы и фактуры идеально имитируют природные.

c) В современном строительстве все чаще для утепления используется базальтовые утеплители. Базальтовая вата, которая лежит в основе популярных утеплителей, отличается высокими изоляционными показателями, которые определяются изначально низкой теплопроводностью самих волокон и присутствующей в структуре влаги. Кроме того, утеплитель базальтовый не поддерживает горение и не выделяет токсичные вещества при нагревании, посему может использоваться для защиты промышленных трубопроводов.

3 Discuss the following proverbs:

“Leave no stone unturned.” (Euripides)  

A rolling stone gathers no moss. (Proverb)  

• Write a paraphrase of each proverb. • Say whether you agree or not, and why.

READING  

4 a) Transcribe the following words:

igneous, metamorphic, sedimentary, plutonic, granite, pumice, dolerite, bedding planes, calcium carbonate, silica, iron dioxide, dolomite, calcareous, siliceous, ferruginous, quartzite, ochre.

b) In what context do you think the following words and phrases will appear in the text?

•natural rocks •sophisticated use •magma •solidification •aggregates •by the weathering and erosion •strength and durability •range in colour •recrystallisation of older rocks •metamorphosed •flooring material

с) Read the text and check your answers:

The term stone refers to natural rocks after their removal from the earth’s crust. The significance of stone as a building material is illustrated by widespread prehistoric evidence and its sophisticated use in the early civilisations of the world, including the Egyptians, the Incas of Peru and the Mayans of Central America. Geologically, all rocks can be classified into one of three groups: igneous, metamorphic and sedimentary, according to the natural processes by which they were produced within or on the earth’s surface.

Igneous rocks are the oldest, having been formed by the solidification of the molten core of the earth or magma. They form about 95% of the earth’s crust, which is up to 16 km thick. Depending on whether solidification occurred slowly within the earth’s crust or rapidly at the surface, the igneous rocks are defined as plutonic or volcanic, respectively. In the plutonic rocks, slow cooling from the molten state allowed large crystals to grow, which are characteristic of the granites. Volcanic rocks such as pumice and basalt are fine-grained and individual crystals cannot be distinguished by eye; thus, the stones are visually less interesting. Dolerites, formed by an intermediate rate of cooling, exhibit a medium-grained structure.

Basalt is a fine-grained stone nearly as hard as granite. It can be melted at 2400 °C and cast into tile units which are deep steel grey in colour. Annealing in a furnace produces a hard virtually maintenance-free, shiny textured surface flecked with shades of green, red and bronze.

Although basalt and dolerite have not been used widely as building stones they are frequently used as aggregates, and cast basalt is now being used as a reconstituted stone.

Sedimentary rocks are produced by the weathering and erosion of older rocks. The natural bedding planes associated with the formation of the deposits may be thick or thin but are potentially weak; this is used to advantage in the quarrying process. In masonry, to obtain maximum strength and durability, stones should be laid to their natural bed except for cornices, sills and string courses which should be edge-bedded.

Deposits of sand cemented together by calcium carbonate, silica, iron oxide and dolomite produce calcareous, siliceous, ferruginous and dolomitic sandstones, respectively. Depending on the nature of the original sand deposit, the sandstones may be fine or coarse in texture. Sandstones range in colour from white, buff and grey through to brown and shades of red depending on the natural cement; they are generally frost-resistant.

Limestones consist mainly of calcium carbonate, either crystallised from solution as calcite or formed from accumulations of fossilised shells deposited by various sea organisms.They are generally classified according to their mode of formation. Many colours are available ranging from off-white, buff, cream, grey and blue.

Metamorphic rocks are formed by the recrystallisation of older rocks, when subjected to intense heat or pressure or both, within the earth’s crust. Clay is metamorphosed to slate, limestone to marble and sandstone to quartzite.

Slate is derived from fine-grained sand-free clay sediments. Slate can be split into thin sections (typically 4–10 mm for roofing slates) giving a natural riven finish, or it may be sawn, sanded, fine rubbed, honed, polished, flame textured or bush hammered.

Marble is metamorphosed limestone in which the calcium carbonate has been recrystallised into a mosaic of approximately equal-sized calcite crystals. The process, if complete, will remove all traces of fossils, the size of the crystals being largely dependent on the duration of the process.

Quartzite is metamorphosed sandstone. The grains of quartz are recrystallised into a matrix of quartz, producing a durable and very hard-wearing stone used mainly as a flooring material. The presence of mica allows the material to be split along smooth cleavage planes, producing a riven finish. Quartzite is available in white, grey, grey-green, blue-grey and ochre colours.

5 Read the text again and answer the questions that follow (1-10):

1. What does the term “stone” refer to?

2. How long has stone been used as a building material?

3. How can all rocks be classified geologically?

4. What is igneous rock?

5. What is the difference between plutonic and volcanic rocks? Give the examples of stones.

6. How are sedimentary rocks produced? What stones are defined as sedimentary?

7. Metamorphic rocks are formed by recrystallisation of young rocks, aren’t they?

8. Can you describe slate?

9. What happens to limestone when metamorphosed?

10. What is quartzite usually used as? Why?

Follow-up

6 a) Find the synonyms for the following words:

excavation, quickly, feature, recognize, show, reconstructed, tint, enable, composed of, aggregation, nearly, equal in size, finish, long-lived.

Дата добавления: 2014-11-29