Civil Engineering Reference
In-Depth Information
parts sand with a grain size of up to 5 mm. The third layer consists of one part
hydraulic lime and three parts sand with a grain size of up to 5 mm, almost the
same mix as the second layer.
Lime cement render
Lime cement render is used a great deal externally. It is somewhat stronger than
lime render and more elastic than pure cement render. From 30-50 per cent of the
binder is usually cement.
Cement render
This is mostly used as an external render in a retaining wall, tanks, pools, etc.,
and can be used on solid concrete walls, concrete blocks, lightweight concrete
blocks, etc. First any cracks or damage to the surface should be smoothed out
with a cement mortar of proportions 1:3, then the surface should be brushed with
a cement gruel of the same mix proportions and finally rendered with a cement
mortar of 1:1 on concrete walls or 1:3 on concrete block or lightweight block
walls. The last treatment can be repeated, giving a surface which is as good as
watertight.
Gypsum rendering
Gypsum rendering is mainly for internal use, especially as a moisture-regulat-
ing layer. This is a common plastering of buildings where brick or concrete
block is the structural material. A mix of one part gypsum to two parts sand is
usual. This sets in 10-30 minutes. Lime can be added to make the gypsum go
further. For stucco work, a mix of three parts liquid lime and one part gypsum
powder is used. More gypsum is needed for relief work in proportions of one
part lime and two parts gypsum. A final coating can be one part lime and one
part marble dust.
Sulphur render
This can be produced by melting sulphur at temperatures from 120-150°C. Sand,
wood flour or the equivalent can be added. It is waterproof but cannot be used
on materials with a high lime content.
Stone surface materials
Natural stone in the form of slate tiles is well-suited to many different uses, e.g.
roof and wall covering and floors. Tiles cut from limestone, marble, syenite,
sandstone and granite can be used as a floor finish, and as internal and external
wall cladding.
