Civil Engineering Reference
In-Depth Information
pollution. Its vapour diffusion coefficient is about as high as that of lime products.
Some silicate paints available on the market have a few acrylates added (to a max-
imum of 5 per cent), which harden and form a 'dispersion-silicate paint'. As long
as the surface material contains lime, added acrylate is not actually necessary. It
can also be assumed that the added acrylate shortens the effective life span of the
paint. For pure waterglass paints, pigment has to be added on site; paint with
acrylate additives can be mixed at the factory.
Cement paints
Cement paints were first used in the 1940s and usually consist of Portland
cement and possibly some lime, which is mixed with a small amount of water
and then added to the pigment and water. They give their best results on newly-
struck concrete or fresh render, but can also be used on brick. In durability and
quality they fall somewhere between lime and silicate products. Pure cement
paint is mainly used nowadays for special treatment of pools and various con-
crete structures, with large quantities of added polymers. Cement paints con-
taining lime only have dolomite and cellulose glue added.
Recipe: Original cement paint
5 litres skimmed milk is mixed with 0.5 to 1.5 kg Portland cement and pigments that are
compatible with lime are added up to a maximum of 5 per cent by weight, to make a gruel.
The mixture is suitable for rough wood panelling and masonry. It has to be stirred while
being used. The pigments suited for this paint are chalk for white, English red, ochre and
other earth colours. The paint is very durable. It was used a great deal by American farm-
ers.
Paints with organic binders
Organic binders consist of synthetic resins, protein glue, drying oils, tar, natural
resins, cellulose products, starch and emulsion.
Synthetic resins
As with glues, synthetic resins can be divided into thermoplastic and ther-
mosetting products. Thermoplastic products must have a hardener added
before painting, and include paints and varnishes based on epoxide, acrylate
and urethane (better known as DD-varnish). Alkyde oil paint is the most impor-
tant thermosetting product. The thermosetting products can be dissolved in
