Современные проблемы промышленного и гражданского строительства на занятиях английского языка. Кузьмина Е.В. - 25 стр.

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Lime Mortar – This is a mixture of quick lime and sand, in the proportion

of a part lime to 2 or 3 parts sand in addition to water. It is the principal

material used for bedding and jointing bricks, stones, etc. The slaked lime is

mixed with the sand and water either by hand or in a mortar mill. The period of

slaking, composition and strength of mortar depends upon the class of lime

used.

Non-hydraulic Lime Mortars must be well slaked before use. This type

can be stored in a heap for several days after mixing, provided the surface is

smoothed over with a shovel to, minimize carbonation by the exclusion of as

much air as possible. As such mortars can only harden when exposed to the

atmosphere, a relatively large proportion of sand must be added to the lime to

assist in the penetration of air for this reason the proportion of sand may be as

high as 4 parts by volume of sand to 1 part lime. These mortars are not suitable

for work below ground level, especially if the ground is water-logged.

Hydraulic Lime Mortars should be used within an hour after being mixed.

Any mortar which has stiffened and cannot be knocked up by means of a trowel

to a sufficiently plastic condition should never be used. The proportion of lime

to aggregate ranges from 1 part lime to from 2 to 3.5 parts sand, and common

mixture being 1:3. These are excellent mortars for all purposes and are

particularly suited for work below the ground level and in exposed positions.

Magnesian and Dolomitic Lime Mortars have a slow-setting an action and

should therefore be slaked for several hours before use. Their properties and

uses are somewhat similar those of hydraulic lime mortars.

Black Mortars. - Ashes or clinkers from furnaces are crushed finely and

ground with the lime in a mortar mill to produce a cheap and strong mortar,

known as black mortar. The ashes should be free from unburnt coal and dust. A

common proportion is 1 part lime to 3 parts ashes or clinker. They are hard-

setting mortars and are suitable for internal walls and for brickwork and

masonry where the color is not objected to.

Cement Mortars. - It is stronger than lime mortar and is used in the

construction for external walls. Cement mortar is now extensively used during

winter, owing to as relatively quick-setting property. It must be used