Building Materials, Third Edition

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 Geotextiles may be placed on one or both sides of the geomemebres
(Synthetic liner) to protect it from installation and design stresses. Such lining systems are
gaining popularity in hazardous and non-hazardous waste landfills. They replace conventional
sand/clay protective layers. Geotextiles are also commonly used in leachate collection and
detection systems in waste disposal facilities. They function as fluid transmission and/or relief
layers.

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Sand-lime bricks can be used as a substitute for clay bricks. They are prepared where suitable
clay for the manufacture of bricks is not available. They are also used for ornamental works.
These bricks are in very wide use in Russia and West Germany. In India these bricks have not
gained much ground although, some structures have been made in Kerala state using sand-
lime bricks.
Sand-lime bricks are made from a lean mixture of slaked lime and fine siliceous sand,
moulded under mechanical pressure and hardened under steam pressure. Constituents of
these bricks are sand, lime, water and colouring pigment. They consist of 88 of 92% of sand, 8
to 12% of lime and 0.2 to 0.3% pigment. Water containing soluble salts or organic matter more
than 0.25%, should not be used in the manufacture of these bricks. Sea water is totally unfit.

Manufacture The sand should be free from clay or mica. It should all pass a 20 mesh and
three-fourths of it should be retained on 100-mesh. If the grains run larger than a 20-mesh, the
coarse particles must be screened out or reduced in a tube mill. A high-calcium lime is preferred
to a brown or dolomitic lime owing to the rapidity with which the high-calcium lime hardens.
The requisite percentage of lime varies between 4 to 10 per cent. Generally the lime is slaked
before mixing with the sand by placing it beneath the brick cars in the hardening cylinder and
allowing the steam to act upon it. Often the sand and lime are mixed dry in a tube mill and the
mixture is then tempered in a special type of pug mill. In some plants the quick lime is slaked