Asbestos and Clay Products

7/26/2019 Asbestos and Clay Products

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ASBESTOS

A number of different minerals containing varying

amounts of silicon, oxygen, calcium and magnesium

qualify as form asbestos but all have one feature in

common, a structure based on long-chain molecules

containing the repeating unit (Si4!!" -#


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AS$%S&S AS A

'%A&' 'A)A*+ung cancerAsbestosis (a chronic

inflammation of the lungs"

$S%&% *+./&S /0&A10102 AS$%S&S

1. Raw asbestos fibres 3ere used as insulation %xample ac5ing for 3alls

and floors 1nsulation of batteries

2. Asbestos textiles 3ere used in belting for conveying hot materials, friction

materials, and as electrical and thermal insulation

3. Asbestos paper 3as used as electrical and thermal insulation and for fire

protection in military helmets, armored car roofs


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4. Asbestos-cement products contained up to 678 ortland cement 'ere the

strong asbestos fibres 3ere used to strengthen the product as 3ell as to

improve thermal insulation properties

5. Asbestos reinforced and filled plastics included both thermoplastic andthermosetting types to 3hich asbestos 3as added as loose fibre, 3oven

textile or paper


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*%/A.&10S 0 %0/.0&%*102

AS$%S&S

1f dealing 3ith the ra3 fibre and 3oven forms of it, protective clothing

should be 3orn, including a respirator, rubber gloves and gumboots

+rilling and cutting of asbestos-cement and other composites should only

be underta5en if the surface can be 5ept 3et and continual damping do3n

is possible to prevent the formation of air-borne dust 9achining processes should only be permitted if adequate exhaust systems

are available to ta5e off the dust-laden air


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CLAY PRODUCTS

&he mineral kaolinite, from 3hich high-quality porcelain is

manufactured ure 5aolinite is an alumino-silicate of the

formula Al:;:Si::':, but natural clays vary 3idely in

composition


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?/ Since ra3

fireclay is relatively expensive, crushed used firebric5 (5no3n as @grog@" isadded to ne3 clay, partly for reasons of economy but also to reduce shrin5age

of the product during firing


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S'A102 /A= *+./&S (i) The plaster mould is flled with slip

(ii) a layer o clay particles collects on the mould surace aswater is absorbed by the mould

(iii) when the shell is thick enough, excess slip is pouredaway

(iv) the resultant 'casting' is removed rom the dry mould

beore being urther dried and fred'.


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'=+*AS&1/


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&'% '%A&-&*%A&9%0& < /A= *+./&S

1. Drin! in 3hich the 3or5 is loaded on to rac5s in large ovens and thetemperature then raised to about !:>?/ in an atmospheresaturated wit"

water #apour. &he humidity is then very gradually reduced so that 3ater

evaporates slo3ly and evenly from the 3or5

2. $irin! is usually carried out in long gas- or electrically-heated tunnel

5ilns through 3hich the 3or5 moves very slo3ly to3ards the hottest one(about !7>>?/", then into the cooling one through 3hich the 3or5 again

moves very slo3ly before being discharged

Asbestos and Clay Products

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