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Cork insulation; a complete illustrated textbook on cork insulation ...

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STRUCTURAL SUGGESTIONS 229<br />

Penetrati<strong>on</strong>.—The Asphalt cement shall be of such c<strong>on</strong>sistency as<br />

to show a penetrati<strong>on</strong> of more than 15 when tested at 32° F. (0° C.)<br />

and less than 70 when tested at 115° F. (46.1° C). (0.2 millimeter<br />

shall be added for each 1.0 per cent, of ash, to give the true pene-<br />

trati<strong>on</strong>.)<br />

Volatilisati<strong>on</strong>.—The loss by volatilizati<strong>on</strong> <strong>on</strong> heating of the Asphalt<br />

cement shall not exceed 1 per cent., the penetrati<strong>on</strong> after heating<br />

shall be not less than 80 per cent, of the original penetrati<strong>on</strong>, and the<br />

ductility after heating shall have been reduced not more than 20 per<br />

cent.<br />

Ductility.—When pulled vertically by a motor at a uniform rate<br />

of 5 cm. per minute in a bath of water, a cylinder of Asphalt cement<br />

1 cm. in diameter at a temperature of 77° F. (25° C.) shall be el<strong>on</strong>-<br />

gated not less than 15 cm. before breaking, and at a temperature of<br />

40° F. (4.5° C.) shall be el<strong>on</strong>gated not less than 3 cm. before breaking.<br />

Outline of the Purpose of Specificati<strong>on</strong>s for Asphalt Cement<br />

for Cold Storage Insulati<strong>on</strong>.<br />

Impurities are a measure of the care with which the Asphalt cement<br />

has been refined and handled. Usually the presence of impurities in<br />

'arge quantities indicates a poor grade of asphalt. Water as an impurity<br />

would act as a diluent and would cause foaming in the kettle. Ash,<br />

3r mineral matter, is not c<strong>on</strong>sidered an impurity if it is a natural c<strong>on</strong>-<br />

stituent of the Asphalt cement, but the cementing value must be fig-<br />

ured <strong>on</strong> the bitumen al<strong>on</strong>e.<br />

Specific Grcznty of the Asphalt cement should be over 1.000 be-<br />

cause Asphalt cements of a pentrati<strong>on</strong> satisfactory for cold storage<br />

<str<strong>on</strong>g>insulati<strong>on</strong></str<strong>on</strong>g> work always have a specific gravity greater than 1.000,<br />

whereas paraffin base and air-blown products frequently have a spe-<br />

j Fixed<br />

:ific gravity less than 1.000.<br />

Carb<strong>on</strong> is to some extent a measure of the chemical c<strong>on</strong>-<br />

i;tituti<strong>on</strong> of an Asphalt cement, and is largely used to determine the<br />

;ource and uniformity of an asphalt. Fixed carb<strong>on</strong> is not free carb<strong>on</strong>,<br />

A^hich latter is practically absent in Asphalt cement, but fixed carb<strong>on</strong><br />

ncludes free carb<strong>on</strong>.<br />

Sulphur and sulphur compounds are ordinarily the cause of the<br />

odor in oils and asphalts, particularly up<strong>on</strong> heating. An Asphalt<br />

i^ement that is low in sulphur compounds is necessary for cold storage<br />

nsulati<strong>on</strong> work.<br />

Solubility in Carb<strong>on</strong> Bisulphide is a measure of the purity of an<br />

A.sphalt cement; and the cementing value, other things being equal, is<br />

proporti<strong>on</strong>al to the CS2 solubility. Any carb<strong>on</strong>aceous material, such<br />

IS coal tar or pitch, is detected by this test.<br />

Melting Point is a measure of the temperature at which the As-<br />

)halt cement will flow readily. The melting point desired is deternined<br />

by the workability of the Asphalt cement <strong>on</strong> <strong>cork</strong>boards when<br />

lipped, and should have a melting point somewhat higher than the<br />

lighest temperature to which it will be subjected in place with<br />

nsulati<strong>on</strong>.

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