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There are two types of cement: Grey cement - used only for construction
purposes, and White cement - for a variety of uses like mosaic flooring,
in cement paints, and as a primer for paints, etc. Grey cement costs
more than white cement because the production costs and excise duty
are higher. White cement also sets faster. For grey cement, the
strength after 28 days of setting is taken as the final strength.
White cement achieves this strength in about three days time.
The cement has to be fine in texture. It should be smooth, dry
and cool to touch. Fineness gives more strength to cement because
the chemical reactions take place faster. Do not buy cement which
is in rough, granular lumps. This indicates it has been exposed
to moisture. Cement is now available in grades and is easier to
buy . For eg: 53 grade cement implies that a cube of cement can
withstand a pressure of 530 kgs per square centimetre. You can check
this on a compressing machine. This is called the breaking strength
of cement. Good cement hardens faster. You can therefore remove
the scaffolding / formwork sooner than usual. You save on centering
and labour costs, and your building is ready much faster.
HOW
TO BUY MARBLE
Marble has qualities and advantages over other stone materials.
It is more durable, attractive and is available in various colours
- white, yellow, red, black and green, which can be used to match
any kind of decor.
 When
used for flooring, it provides a highly elegant finish which is
hard, durable, dust free and suits Indian climatic conditions.
Marble possesses great reflective qualities and its crystalline
structure gives it a bright lustre. Marble is broadly classified
into two categories - white and coloured. For exterior finishes,
sound marble with uniform quality should be used. If the marble
contains flaws, voids, is discoloured by veins and lines, it should
be treated for soundness by spraying surface treatment compounds.
Good marble should comply with the following requirements:
1.If immersed in cold water for 24
hours the marble should not gain more than 0.4% in weight.
2.On Moh's scale (a scale of 1 to 10 to measure hardness
of solid materials, where talc, the softest material occupies No.1
position, and diamond, the hardest material is No.10), hardness
of marble should measure more than 3.
3.When you buy marble slabs and tiles see that they are square
edged. Tiles and slabs are available in the following finishes:
Sand abrasive finish - a flat non-reflective surface.
Hone finish: a velvet smooth finish with little or no gloss.
Polished finish: a highly glossy finished surface which brings out
the full colour and character of marble .
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