RRR f
2w is ironstone slag impregnated with tar oils. It is impervious to water and used in
road pavement.
2' is a composition of limestone and coaltar. It is heated before use.
2w is used for road pavement. Soft rock materials such as limestones blast
furnance cinder, etc. are heated in a furnace and then mixed with boiling coal tar, pitch and
creosote oil. The mix is applied in road soon after cooling and rolled.
IVR sgr
Most pitches used in building are obtained either as the residue of the direct distillation of
crude tar produced by the high temperature carbonization of coal as a waste product.
However, by fluxing back such pitch residues with high boiling coal tar distillates the material
can be suitably conditioned to give products of desired softening points for a number of
particular uses.
Coal tar pitch is classified on the basis of softening point into four grades as given in
Table 18.1.
2IV I 22g22q
h w 2
e272
2
2
2
2272
2 2@w A @w A
PUH"g2QHH"g
@w A2@w A
2
RS&SS" I(PH&I(QH R V PS H(SH
2
2
SV&TV" I(PP&I(QP R V PV H(SH
r2
2
UH&VH" I(PP&I(QP Q R QH H(US
r2
VP&WP" I(PV&I(QV & & QS H(VH
g
Carbon 75%
Hydrogen 8%
Oxygen 16%
Nitrogen 1%
Ash and sulphur Little
Pitch is extensively used as ingredient in a number of water proofing, protective and
binding compounds in masonry, timber and steel structures. It is also used in the manufacture
of tar felt and flooring mastics, and as a base for coal tar paints designed mainly for cold
applications. The pitch paints set by drying of the solvent.
IVS erev
Asphalt is a natural or artificial mixture in which bitumen is associated with inert mineral
matter. It is black or brownish black in colour. At temperature between 50–100°C it is in liquid
state whereas at temperature less than this it remains in solid state. Because it is a thermoplastic
material it softens as it is heated and hardens as it is cooled. It is the basic paving material in
use today.