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Artificial Stones

Where durable natural stone is not available at reasonable cost, artificial stones, 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:
  1. Concrete Block are cast at site in the construction of piers or cast in moulds for steps, window sills, etc.
  2. Ransom Stone 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 .
  3. Victoria Stone are granite pieces with the surfaces hardened by keeping immersed in soda silicate for about two months.
  4. Bituminous Stone: 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.
  5. Imperial Stone: 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.
  6. Artificial Marble 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 2 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.
  7. Garlic Stone is produced by moulding a mixture of iron slag and portland cement. These are used as flag stones, surface drains, etc.
  8. Mosaic tiles: Pre-Cast concrete tiles with marble chips at top surface are known as tiles. They are available in different shades and widely adopted at present.
  9. Terrazo: This is a mixture of marble chips and cement. It is used for bathrooms residential buildings, temples etc.

Advantages of artificial stones:

  1. Cavities  may be kept in artificial stones to convey pipes, electric wires etc.
  2. Grooves can be kept in artificial stone while it is being cast which are useful for fixing various fittings.
  3. It can cast in desired shape
  4. It can be made in a single piece and hence trouble of getting large blocks of stone for lintels, beams etc is avoided.
  5. It can be made stronger than natural stone
  6. It is cheap and economical
  7. It is more durable than natural stone
  8. Natural bed is absent  in  artificial  stones  and  hence, the question of taking precautions with respect to the natural bed of stones does not arise.

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