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      Chapter No. 9

           GLASS General
  Glass has been an important engineering
material, since old times. Glass industry has
progressed very rapidly and new techniques
have been developed with the help of which
glass of any type and quality can be produced.
The methods of glass manufacture            have
changed and improved, resulting in higher
production rates, superior glass, and large sheet
GLASS Classification of Glass
   Glass is a hard brittle, transparent, translucent material. Its
structure is amorphous. It is made by fusion of silica with
varying proportions of oxides of sodium, potassium, calcium,
magnesia, iron and other mineral. All these materials when
melted, form a number of metallic silicates. Hence glass may be
said as a material consisting of a number of metallic silicates.
For the purpose of classification, glass may be grouped into
following four categories.
    Soda-lime glass (Na20, CaO, 6Si02)
    Potash-lime glass (K20 CaO 6 Si02)
    Potash-lead glass (K20, PbO, 6 Si02)
    Common glass.
          GLASS Properties of glass
It   is extremely brittle and is available in beautiful colors.
It   is affected by alkalis, but not by air or water.
It   has amorphous structure.
It   has no definite melting point.
It   can be polished.
It   absorbs, and refracts light.
It   is not easily affected by chemicals.
It   can be cast into any desired shape.
Glass    can be welded by fusion.
       PLASTICS Introduction
       Plastic was invented by Schonbein in 1856. He
named the product as cellulose. John Wesley Hyatt
developed a new material in 1890 and named it celluloid. In
this century Dr. Bakeland, a Belgian scientists, produced a
product known as Bakelite. The most significant
development in plastics occured mainly in the period lying
between two world wars. In 1924 an Austrian Scientist Mr.
Pollak prepared a substance from urea and formaldehyde.
This substance was as transparent as glass.. Now the plastic
has been improved to such an extent that it has assumed
important place as engineering material.
   PLASTICS Composition of Plastic
      It is an organic substance prepared from natural or
synthetic resins in which other materials like fillers,
solvents, plasticizers, might have been added or not. In
general terms, plastics may be stated as compounds of
carbon with other elements such as oxygen, hydrogen
nitrogen. Carbon combines with itself and other elements
and forms more complicated compounds.
           BITUMEN Introduction
       Bituminous materials have been known and used in road
construction since ancient times. They were used as a mortar and
water proofing agents. Early bitumen was of natural origin, found in
pools and lakes: Many of these pools and lakes exist even to-day.
The bitumen lake on the Trinidad island and the Bermudz
deposit in Venezuela are the largest known sources of natural
       Now a days bitumen is mainly used in the construction of
roads. It is also used in building industry inform of timber
preservative, It is also used in so many other fields but its use in
those field is not predominant.
               BITUMEN Bitumen
       As per I.S. 334-1951 bitumen is defined as a non-crystalline
solid or viscous material having adhesive properties, derived from
petroleum either by natural or refinery process. It is substantially
soluble in carbon disulphide.
        The greatest proportion of bitumen is obtained from crude
petroleum. It is obtained by fractional distillation process in which
the simpler components of the crude petroleum such as white spirit,
kerosene, fuel oil, light, medium and heavy lubricating oils which
have lower boiling points are evaporated, leaving behind the
bitumen. It is black or brown in colour. Bitumen may be extracted by
distillation process or cracking process. Mostly distillation process is
     BITUMEN Straight run bitumen.
 The bitumen which has been distilled to a definite viscosity or
penetration without further treatment is known as straight run
bitumen. During processing, by regulating rate of flow and
temperature, bitumen from very soft to a very hard consistency grade
can be produced. Before this bitumen can be used it has to be
processed to reduce its viscosity either by heating, addition of cut, or
emulsifying agent. This bitumen is mostly used for road
      BITUMEN Air blown bitumen.
Special properties can be developed in semi-solid bitumen
by blowing air through the residue, still in hot condition.
This bitumen is sometimes called oxidized bitumen also.
This bitumen is not used in paving mixes, but is a useful
material for roofing, battery boxes, water proofing, etc. It is
widely used, as crack and joint filler material, for concrete
      BITUMEN Cut back bitumen.
       Cut back is defined as a bitumen, whose viscosity has
been reduced by the addition of a volatile diluents. Volatile
diluents are gasoline, kerosene and high boiling-point light
oils. Cut back is used, when it is essential to have a fluid
binder which can be readily poured or sprayed at relatively
low temperature. The important features of a cut back are its
viscosity at the temperature of its use and also the rate at
which it sets. The rate of setting is the rate at which solvent
evaporates from cut back.
            BITUMEN Emulsions.
It is a combination of water, bitumen and an emulsifying
  agent. Bitumen does not dissolve in water. But when heated
  bitumen and water are mixed together and agitated. The
  bitumen disperses in water inform of spherical globules of
  about 2 micron diameter. To prevent bitumen spheres from
  coalescing, an emulsifying agent is added in the emulsion
  which remains dissolved in water. Soap is used mostly as an
  emulsifying agent. Depending upon the stability of the
  protective coating of emulsifying agent the emulsion may be
  classified as Rapid setting (R.S.), Medium setting (MS.) and
  slow setting (S.S.).
             BITUMEN Emulsions.
Emulsions are always stored in air tight drums. It is used
 mostly for the construction of roads. It is not required to be
 heated, before use and as such are very useful for the places'
 where heating of the bitumen has to be avoided. Emulsion is
 mixed with road metal and applied. When emulsion changes
 its colour from brown to black, it is said that emulsion has
 started breaking. As the emulsion starts breaking, it starts
 binding the aggregate. Emulsion can be used for soil
 stabilization, patch repair works of bituminous roads, etc. Its
 main feature is that it can be used in wet conditions also.
        BITUMEN Tests for Bitumen.
In order to ascertain the properties of the bitumen, it may be
  subjected to tests as follows.
  Penetration test.
 This test is used to determine the hardness of the bitumen.
  This test consists of a needle of standard dimension which is
  loaded by 100 gm and made to penetrate vertically in the
  bitumen at 25°C for a period of 5 seconds. The penetration
  of the needle is measured in units of 1/100 cm. Bitumen is
  graded according to the penetration. It is written as 30/40,
  80/100, 60/70, etc. 30/40 grade bitumen means that under
  standard conditions of temperature, the needle penetration
  varies from 0.30 to 0.40 cm.
        BITUMEN Tests for Bitumen.
 Softening point.
This test is done to determine temperature susceptibility of
 the bitumen. This test is done by ring and ball equipment.
 The softening temperature is that temperature at which a ball
 of bitumen will flow vertically for 2.54 cm through the ring
 on which it was placed. This temperature for usual bitumens
 lies between 35°C and 70°C. As per IS 702-1961 bitumen
 has been classified into grades such as 62/25, 75/ 15, 75/30,
 85/25, 85/40. The first figure gives softening temperature in
 degrees centigrade and second figure gives penetration in
 1/100 cm units at 25°C.
        BITUMEN Tests for Bitumen.
Ductility Test.
This test is carried out to ascertain the ductility of the
 bitumen. A standard briquette of bitumen is prepared from
 bitumen and stretched at predetermined rate at 75°C in a
 stretching machine. The distance of stretch of the briquette,
 before it breaks determines the ductility of the bitumen.
 Ductility for various grades of bitumen varies from 5 to 100.
 For satisfactory use in road pavement, value of ductility
 should not be less than 50.
        BITUMEN Tests for Bitumen.
Float test.
This test is carried out to determine the consistency of the
 bitumen. For this test an aluminum float having standard
 sized hole at the bottom is used. The specimen of bitumen to
 be tested is filled in the coller fitted in the hole and
 temperature of the water bath in which this float is left, is
 raised to 50°C. The temperature of the bath is maintained at
 50°C. The time required in seconds for water to force its
 way through bitumen plug is noted. The higher the float test
 value, the stiffer is the bitumen.
       BITUMEN Tests for Bitumen.
Flash point and fire point test.
       Flash point is the lowest temperature at which the
 vapour of a bituminous material momentarily catches fire in
 the form of a flash under specified conditions of test.
       Fire point is the lowest temperature at which
 bituminous material gets ignited and burns under specified
 conditions of test.
       The knowledge of these points is of interest mainly to
 the users, since bitumen must not be heated beyond these
 points. The flash point tells the critical temperature at and
 above which suitable precautions are required to be taken to
 eliminate the danger of fire during heating.

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