|
REHABILITATION OF THE MOSTAR |
|
|
|
NEWSLETTER 10
APRIL 30, 2003 MOSTAR, BOSNIA AND HERZEGOVINA |
||
|
Pouring the lead into channels LEAD Lead is known from ancient times (~ 1000. years B.C.). Its name comes
from Latin word plumbum which means fluid silver.
Leaded cramps It’s a soft, bleary grey
metal which tarnishes on air from created protective layer of oxide and
carbonate. It is resistant to corrosion and liquefiable only in oxidizing
acids, like nitrite acid. It’s melting point is low, 327,4°C;
significant amounts of poisonous lead vapour vaporize from melted lead even
much below the melting point (1750°C).
Test pouring of
dowels with lead §
In
the fine grained porous Eolithic surface of Tenelija the lead flows on a film
of air on the stone surface pores: polishing of the channels is not necessary
to encourage flow but it can be of help in problematic areas like low
gradient channels. §
Mortar
layer in the stone joints will not interfere with channels for lead pouring,
and will not obstruct them.
Thermometer So, as you can
see from above mentioned, great care should be given for the lead melting and
pouring. This final step of the stone assembling is very important for the
durability of the whole construction. If the temperature of lead is under the
370°C, there is a possibility that the
channels become stocked by the cooling lead, and if it is over 430°C, later cracks are possible.
Returning the
unused lead into the vessel That was the reason for ordering special
melting equipment. It consists of the metal vessel, easy to carry and
equipped with the thermometer and metal can for pouring the lead into the
gaps. It was made in workshop in Korčula, by Mr Vladimir Šeparović artist and
expert in metal treatment. Placing the rest of the stone blocks in that
row was continued the same day. As it is planed, mounting of one arch row
should be finished each day. It started with first five rows on the left
bank, in order to equalize with the level on the right bank, where the rows
weren’t even demounted because their condition was satisfying. After reaching
the same level on both sides, alternately masonry will start. That way, weight
and forces will be able to dispose smoothly. At the same time, lateral walls,
fillings and inner rib will be filled.
Placing the stone Necessary materials for all of these phases
are already determined and prepared. They all were chosen first by their
visual characteristics, and after that sent to the laboratory for further
tests and examinations. For most of the materials, several samples had to be
chosen for the laboratory tests, so only one of them could be approved. All of them now have satisfied the quality
compliance tests.
Principle of rows assembling
Pouring
of lead into dowels On the same place, in Komos, after chiselling of row is finished and
its dimensions verified, holes for cramps and dowels are chiselled. Dowels
are built into the blocks from upper side and poured with lead. After the
Supervision finishes the inspection of row dimensions and chiselling quality,
blocks are sent to the
Leaded
dowels, ready to be built in Great attention is given not to damage the
blocks during transport, because by damaging a single block in a row we would
have to start chiselling the entire row again. Knowing that the blocks are
expensive and valuable, and that every repeated procedure means great delay
in dynamic plan – precaution measures that are undertaken for safer transport
are enormous.
Transport of blocks |
Before proceeding to assembling works, it has to be pointed out that
stones, (following ancient technique), should be connected with mortar and
with additional metal strengthening devices that are anchored to stones by
melted lead poured in purposely built slots (gaps). For the above reason special expertise and devices for managing the
lead are required and the following matters should be underlined: §
Lead is strongly toxic: for melting and pouring
works, adequate safety precautions are necessary. §
It will be necessary to pour lead both off-site, and
on-site. The risk of fire that may be caused during lead melting will be
strongly limited by protecting the wooden deck. §
Lead should be perfectly melted (370 – 420”C) before
it is poured directly into stone channels with no waiting and no different
route, this to avoid premature solidification. Vessel for melting of lead §
Exact composition of lead to be used will be
determined and tested with the Quality Compliance Tests. §
No water (not even hot water) will be preliminary
poured in stone channels or slots to avoid vapour explosion when lead is
poured: stone should be perfectly dry. §
No thermal shock is suffered by the Tenelija stone
due to lead pouring. §
Stone channels and slots should be accurately
cleaned from stone powder before lead is poured. §
Prior the pour any trace of dirty or slag should be
removed from the surface of the liquid lead. Ceremony of placing the first
stone PLACING THE FIRST STONE INTO THE ARCH OF THE BRIDGE On 14.04.2003, at Attendant guests Many guests attended the ceremony, the mayor
of Mostar Mr. Hamdija Jahić, deputy mayor Mr. Ljubo Beslić, director of Project
Coordination Unit Mr. Rusmir Ćišić, project manager Mr. Tihomir Rozić, representatives
of Supervision, of Contractor, and many journalists and TV networks. A large
number of citizens of Mostar came and enhanced this grate moment with their
presence. Delegation
on the centering
Ablation of blocks on the
spot In Komos, blocks are chiselled by rows: by templates prepared in advance
for upstream and downstream forehead of the row, rough treatment of the stone
is done first and then refined one. This procedure is very precise, because
we know that the millimetre accuracy is required. No mistakes in this phase
are allowed, because the assembling precision of the entire arch fully depends
on this step.
Chiselling of rows in
Komos Every stone-cutter has its identification card and we know precisely
for which phase he is qualified and what he can do. The best ones are working
on finalisation of the visible stone surface, because it has to be the exact
copy of the one that used to be on the old Supervision team is strictly following all of these works.
A row with chiselled holes
for dowels WEB CAMERA Novelty in presentation of reconstruction of
the
Camera
on the left bank This is a common project of BH telecom and
Bihnet, and their pages are available on the following addresses: http://www.starimost.telecom.ba/indexie.htm i http://www.stari.bih.net.ba/indexie.htm
Background
for the web page WEB PAGE In the last Newsletter, we
announced that our web page is in the process of construction. Now we are
happy to be able to give you its correct address: The page is in two languages: from home page
you can enter Bosnian and English version. In column ABOUT US you can get
basic information about the company and the list of the most important bridges
built so far. In the column CONTACT you can get address of the company or
make a contact, and PRESS contains Newsletters and slide show which presents
all that Contractor has done to date. Addresses of the World Bank, UNESCO and PCU
you can find under LINKS. PHOTO GALLERY has photos of different phases of
reconstruction and FAQ answers frequently asked questions to the Contractor. |
|
This NEWSLETTER
was made in accordance with prevailing articles of the Contract No
002/2002 about the Rehabilitation of the