The type of plaster and mix proportion of its
constituents is chosen, depending on location of surface (exposed or interior),
durability requirements, finishing requirements, and availability of binding
materials. Cement is today the most common plastering material because of its
wide availability and quick application. Although, equally good plasters can be
made with lime, but greater skill and time required for its application has led
to its decline, apart from special applications such as conservation of
heritage buildings.
Grade 43 cement is most suitable for plastering.
Grade 53 cement has a faster setting with a greater heat release, causing
cracks in plaster. Therefore, it should not be used without good quality
control and supervision.
Sand is the major ingredient of plaster and its
quality has a significant influence on performance of plaster and its cost.
Sand for plastering should be clean and not contain minerals, clay, organic
matter and silt. For conventional smooth plaster, all the sand should pass
through a sieve with 2.36-mm opening size. For coarsely textured decorative
work, a larger sieve size of 4.75mm can be used. Oversize particles (and lumps)
should be removed by sieving
If the clay and silt content in sand is more than
10%, then it should be washed before use. If there is any doubt about the
percentage and type of clay in the sand, expert advice should be taken.
For external work and undercoat work, coarse sand
should be used. For finishing coat of plaster, fine sand such as river sand
should be used
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