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34
UNIT 6
TEXT A. Gas concrete.
Lime and silica are ground together to very fine limits. The siliceous
material can vary considerably in its composition. Much use is made of such
waste materials as fly ash from power-stations, blast furnace slag, as well as
natural pozzolanas, pumice, etc. The degree of foaming in the gas concrete, and
thus its specific gravity, is determined by the amount of aluminium powder or
other agent added. The practical limits of the final density are between 13 and
90 Ib. Per cu. ft. If he gas concrete is allowed to harden on its own, it usually
takes about three weeks before, the final strength is achieved. It is more
customary to accelerate the setting of the gas concrete by steam hardening it in
autoclaves with superheated steam at about 140 Ib. per sq. in. The steam
hardening process takes about 15-20 hr. Air-cured gas concrete can be used for
the manufacture of special components for the refrigeration industry. Such
blocks are cast to special dimensions.
Gas concrete can be cast horizontally to form roomsized outer wall units.
It is possible to incorporate electric conduit pipes, piping for the cold and
hot water systems and also drainage pipes. The units usually include windows
and doors, and are reinforced by embedding steel mesh in the mix.
Gas concrete can be used as thermally insulating floor screeds or as an
additional thermally insulating layer a top of concrete roof.
Cast gas concrete is often used as the thermally insulating layer in
“sandwich wall” units.
Gas concrete is often used as a thermally insulating layer when casting
buildings by a continuous easting technique.
Text B. Steam treatment process to produce thermoplastic materials and
hydraulic cements
This invention relates to the manufacture of thermoplastic materials and
hydraulic cements from certain glass compositions. More particularly, this
invention relates to the manufacture of such products through the steam
treatment of glass powders in the alkali metal silicate composition field.
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