Page 185 - CW E-Magazine (8-4-2025)

Free to Die

remove most possible liquids and do not Overbridges on main roads of cities Rs. 3,500-crore. All small and large
produce tar at all. Their residue is petro- Of late there is a trend to construct vehicle owners paid heavy toll for over
leum coke. Those who do not distill overbridges on all major intersections 25 years.
hydrocarbons to the last drop, produce of cities. Currently, what is being done
between 3-5% tar of the refi ned crude. is construction of very strong bridges A simpler idea is to create round-
We fi nd the grog gets separated from to carry heavy traffi c and allow small abouts on both sides of the highway as
the tar in the fi rst rain. This happens due vehicles to pass under it. The bridge is shown in the image. The main traffi c
to poor wetting of the grog with tar. Lot required to handle large vehicles like 28 should be ‘VIP’ traffi c and given prefe-
of research has been done on this pro- toner trucks, heavy earth moving equip- rence, just like in railways. It should
blem, and anti-stripping agents are ment, industrial equipment, windmills not be diverted in any direction. For
recommended to be used in tar. This and its components, heavy machinery example, all bridges from Dadar to
happened in India as far back as 1975 and (mainly imported), etc. The bridge is Thane – particularly the ones at a sim-
anti-stripping agent has been specifi ed required to be strong enough to handle ple crossings like Ghatkopar, Vikhroli,
since then. However, the contractors do these. Once the bridge is in place, there Bhandup and Mulund – should not be
not oblige, fearing very long life of the is not much space left for heavy objects rebuilt whenever they go out of service.
roads. It is diffi cult to monitor correct to move under the bridge. Theoretically, Instead, an overhead bridge should
addition and use of right materials. there is nothing wrong with this model. be provided with two roundabouts on
But it causes a lot of inconvenience to both sides. Additional space should be
Government can force the refi ne-
ries to add antistripping agents to the tar users who have to continuously go up bought from residents if required. An
and come down. This hampers speed. action like this will need long-term
to improve compliance. Once added, it In a city like Mumbai, which has strictly planning, even extending to 100 or 200
cannot be removed.
north south movement, the cost of years. But such a plan has to be in place.
There are other options too. construction and the time taken for con-
 Refi neries can also add 2% natural struction is unreasonable. I understand, Flow of water should be the highest
rubber latex to the tar in hot con- Mumbai city’s 55 fl yovers costed over priority
dition before it is packed. This has At times I am surprised to see the
made a huge difference to roads in skills of artisans engaged in the job
Kerala. of road construction. They seem to be
 I have also studied the possibility completely devoid of common sense.
of placing a thin layer of dry Ordi- If a person working on the construction
nary Portland Cement (OPC) on the B D C of a drain notices that the hole provi-
tar road. For this, cement powder ded for fl ow of water is about 15 cm
should be spread on freshly pre- A A
pared road and then rolled over. This
layer can be just about 1-mm thick.
Thus, cement consumption would Plan for changing direction on highways
be about 2-3 kg per m of road. This A, A’ – Highway
2
B & C are circles for cross over, may have signals for monitoring
layer should be applied only in win- D – Overbridge for light traffi c
ter or summer season. Over a period, above the level of the road, why does
the cement gets embedded in the he continue his work? It reminds me
tar. Whenever it rains or the cement of a story of two workmen. One was
comes in contact with water, it hard- digging a hole in the ground and other
ens and provides a very long life to C was fi lling the holes. Amused, a passer-
the road surface because of its very by asked the reason. He was shocked
high abrasion resistance. Refi neries D to hear the answer that they were sup-
can also consider a special grade B posed to be a team of three persons and
of tar enriched with grey cement to A A were to plant trees in the holes. But as
provide improved life to roads for the second workman had not reported
the top-coats of the road, probably on duty, they were doing their job
at no extra cost as grey cement costs without planting the trees. This is an
only 10% of the price of the tar. If adequate space is not available in some places, over example of mindless working! V.C. Malshe
bridges can be constructed at an angle

Chemical Weekly April 8, 2025 185

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