22 VIQIT espsgsev2yxi
Where durable natural stone is not available at reasonable cost, artificial stone, also known as
cast stone becomes the choice. Artificial stone is made with cement and natural aggregates of
the crushed stone and sand with desired surface finish. Suitable colouring pigments may be
added. However, colouring should not exceed 15 per cent by volume. Cement and aggregates
are mixed in proportion of 1:3.
Artificial stone can be moulded into the most intricate forms, cast into any size, reinforced
to have higher strength, are most suitable for face work, since grooves, rebates, etc., can be cast
easily and are economical. Some of the artificial stones available are as follows:
g
f are cast at site in the construction of piers or cast in moulds for steps, window
sills, etc.
are prepared by mixing soda silicate with cement to provide decorative flooring.
These are also known as chemical stones. These have compressive strength of about 32 N/mm^2.
are granite pieces with the surfaces hardened by keeping immersed in soda
silicate for about two months.
f
X Granite and diorite are impregnated with prepared or refined tar to form
bituminous stone. These are used for providing noise, wear and dust resistant stone surfaces.
s
X Finely crushed granite is washed carefully and mixed with Portland cement.
The mix is moulded in desired shape and then steam cured for 24 hours. The cured blocks are
immersed in silicate tanks for three days. These stones are similar to Victoria stones.
e
w can be either pre-cast or cast-in-situ. These are made from portland gypsum
cement and sand. In the precast variety, the cast-stone is removed after three days. On the fifth
day of casting these are treated with a solution, liquid fluorite of magnesia. It is then washed
and wrapped in paper for 24 hours and then once again treated with the liquid. After one
month the stone is polished by rubbing emery over the surface with a linen rag ball dipped in
mixture of lime water and silicate of potash and then the process is repeated without emery. It
is used for external works. Cast-in-situ variety is made by laying the mix on canvas, in thickness
about 1.5 mm more than the required thickness of the stone. The surface is rubbed over and the
airholes are filled with mix. Grinding is done by hand or machine. The surface is then rubbed
with a polishing stone. Final rubbing is done with a ball of wool moistened with alum water
dipped into a 1:3 mix of hartshorn powder and diatomite.
q
is produced by moulding a mixture of iron slag and portland cement. These are
used as flag stones, surface drains, etc.
QIU evsgesyx2yp2yxi
Of the total amount of stone quarried for the building industry, about 75 per cent are used
directly for concrete constructions and road making, the balance find applications in the
manufacture of cement and other binding materials, in the chemical industry, as metallurgical
fluxes, and for making wall from natural stones.