Restricted
UNDP/BUR/78/023
Technical Report
BURMA
Preservation and Restoration
of National Monuments and Artifacts
at Selected Sites
Conservation of
Historic Brick Masonry
in Pagan
by J.C. Yarmola
Serial N o . F M R / C C / C H / 8 7 / 2 1 9 ( U N D P )
United Nations Educational,
Scientific and
Cultural Organization
United Nations
Development
Programme
Paris, 1987
BURMA
Preservation and Restoration of National
Monuments and Artifacts at Selected Sites
CONSERVATION OF HISTORIC BRICK
MASONRY IN PAGAN
by
J.C. Yarmola
Report prepared for the Socialist
Republic of the Union of Burma by
the United Nations Educational, Scientific
and Cultural Organization (Unesco)
acting as Executing Agency for the United
Nations Development Programme (UNDP)
United Nations Educational,
Scientific and Cultural
Organization
United Nations
Development
Programme
UNDP/BUR/78/023
Technical Report (Yarmola)
FMR/CC/CH/87/219(UNDP)
6 April 1987
© Unesco 1987
Printed in France
Foreword
The consultant spent one month in Burma from 31 July to 21 August 1986
and visited several monuments in Pagan with U Than Aung, Civil Engineer, and
Pierre Pichard, Architect and Coordinator of the Pagan Programme. Two consultants
were expected from other countries but neither was able to join Burma during that
period.
The restoration of the masonry in Pagan is an imperative necessity.
Every year several temples, monasteries or stupas are lost. The main reason
is poor upkeep of material which has become increasingly fragile with age. The
heavy rains wash away the mud mortar, paintings are damaged, vaults fall in,
stucco decorations become detached from the cornices and the walls and large
sections of walling collapse.
Many of the monuments were damaged by the earthquake that occurred in
July 1975 and need restoring and strengthening for that reason. However, before
any therapy is administered, it is essential that the monuments should be made
damp-proof and water-proof. Initially, therefore, the best advice must be: point
the joints and then, point more joints. Pointing and water-proofing are mainly
necessary on terraces and cornices and at the base of the walls. Pointing is a
very delicate task and will be described in detail below.
- ii TABLE OF CONTENTS
Pages
Foreword
i
THE STRUCTURAL CARACTERISTICS
1
ON MORTARS IN PAGAN BRICK STRUCTURES
3
ON THE INJECTION OF GROUTS
6
RESTORATION AND REINFORCEMENT
8
REPOINTING AND RESTORATION
10
REBUILDING
10
GUIDELINES OR MEMENTO ON THE INJECTION OF GROUTS
11
MEMENTO ON POINTING
15
ON REINFORCED CONCRETE PROTHESIS
18
MEMENTO ON BRICKS
19
ON MAINTENANCE AND REPAIR
19
CONCLUSIONS
20
BUR/78/023 - Preservation and Restoration of Rational Monuments and Artifacts at
Selected Sites - Conservation of Historic Brick Masonry in Pagan
TECHNICAL REPORT
THE STRUCTURAL CHARACTERISTICS
1.
The structural characteristics have been treated in a report drawn up
by the Rangoon Institute of Technology,in January 1983 and quoted by the Institute
of Earthquake Engineering and Engineering Seismology of the "Kiril and Metodij"
University, Skopje, May 1983 (UNDP:Unesco Project BUR/78/023). *
2.
All the structures except the upper parts and the decorations are heavy
and massive. They form walls, pillars and vaults.
Walls and Pillars
3.
The walls and pillars, made of flat bricks, are composed of two "skins"
or facings of stretcher-bricks with very few headers to create a firm liaison with
the core of the wall, or "filler". Although bricks of different dimensions can
be found, even in a single monument, the common average size is 36 cm. x 18 cm. x 6
or 8 cm. Facings are usually 18 cm. thick and very carefully laid, with extremely
thin horizontal joints not more than 0.0> cm, and often bricks in direct contact.
This stretcher-bond, almost without perpeuds, has been obtained, as was common in
early works i n Western Europe, by a concavity in the beds.
In Pagan
the concavity is about 1.5 cm to 2 cm for 18 cm. The upper bed is concave and the
lower bed is level. As a result the mortar is protected by the very thinness of
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the joint in the facade and no water is retained. The
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joints of the core, or filler, are thicker, from 2 cm to
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3 cm. The lack of headers and the difference in thickfl-V^i'tVi -î?c^"i>" £t;V7-v::v ness of the ioints in the core and in the facings are
factors of weakness as the bearing capacity of the core
will most probably not be the same as the bearing
capacity of the facings.
1
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Facing filler
4.
Another difference between the core and the facings is the moisture
content. Both old and new bricks in Pagan are porous and the mortar found was
"clay puddle" or "clay mud". During the monsoon season, the moisture content
varies between the facings and the core and the clay mortar is wet. The humid
clay lubricates the surfaces and, what is more, may cause the clay puddle to swell.
When damp, bricks become fragile and lose part of their bearing capacity. Those
that had fallen from the base of the outer facings had often crumbled because
the dripping effect had made the lower layers of masonry more humid than the others.
Damage was also noticable below.
* Institute of Earthquake Engineering and Engineering Seismology, University
Kiril and Metodij", Methods for repair and strengthening the national monuiaents
in Pagan, Burma, VOL I-V, Skopje - Serial N° 18115 83-30/1-5
- 2 -
Every year several temples, monasteries or stupas are lost. The main reason
is poor upkeep of material which has become increasingly fragile with age.
The heavy rains wash away the mud mortar... large sections of walling collapse.
The "weak" corner of this monastery could not hold up any longer : the base of
the walls, rain-washed and lubricated, gave way on 10 August 1986.
Ten monumen t s
were ruined
in 1983.
- 3 The Vaults
5.
The vaults are of varying shapes.* Burmese vaults are quite original
and their structure is very interesting indeed. They were probably built without
any frame-centring as the voussoirs are laid with thin layers of shaped bricks
about 8 cm thick. The bond of mortar was sufficient to allow an arch, once
completed, to stand by mere compression of the voussoirs.
6.
The walls have no headers, and the perpends are set in a straight line.
In some cases, bricks can be found on end courses as well as in the walls,
probably to ensure better distribution of stresses.
7.
Depending on the span and the rise of the vaults, one, two, or even
three arch-bands or "rolls" are found. Flat arches or "bond lintels" are built
in the same way.
8.
There are no headers in the stretcher-bond of the facings to provide a
better tie to the core, and no headers in the bond of the vaults to fix the flat
arches to the haunches.
9.
The haunches are made of very carefully-cut brick layers and form a
kind of "corbelling" to support some of the weight, probably at the springer level.
10.
In the brickworks of Pagan monuments, the lack of a liaison between the
bond of the facings in walls as well as in vaults and the core, seems to be due to
a strictly geometrical concept and to the tackiness of the mortar used.
11.
Plaster was applied to the bricks after the walls and the vaults had
been re-surfaced with sharp chisels about 2.5 cm wide. This covering protected
the masonry for centuries and very well-built structures still resist the action
of the rain quite well, although the plaster has flaked off as the joints are very
thin.
In structures with joints more than 0.1 cm wide, however, the erosion
effect is very marked. Ten monuments were ruined in 1983. Consequently, it is
essential that the buildings should be kept as dry as possible.
ON MORTARS IN PAGAN BRICK STRUCTURES
12.
Visual investigation has shown that the bricks were laid with a claypuddle and partly sandy mortar, and there is no reason to believe that there was
lime in the batching. However, national specialists imply additivies of organic
origin which have completely vanished after eight centuries.
13.
The internal facings were plastered, and the external facings were
covered with a hard lime mortar to provide stucco decoration, sometimes carved,
sometimes moulded.
*
See "Conventions and Terminology" by Pierre Pichard in the "Inventory of Pagan
Monuments", in preparation, point 9, pages 15 to 18: "Vaults".
- 4-
a) as bricks are still hand-made locally,
any re-building should be carried out with
bricks of same size as those formerly used.
Special moulds should be provided for each
restoration.
b) injection of grouts is the only way to
fill cracks. Prior to injection, masons
should point the cracks with recessed joints.
The colour and the grain of the mortar are
very important.
c) recessed joints with dark mortar might
look better.
The injection of grouts is the only cure
for this disease, but care should be taken
not to create a "strong point" where the
stresses would converge.
Another solution might be to re-build this
part. It would be a matter of "scale".
The cure must not
be worse than the
disease.
*í i
- 5 -
14.
A recipe for an organic additive is given in a Burmese poem: nine
parts of "leather juice" or animal glue from ox-hide; seven parts of a paste made
with the bark of a tree called "UN DUNG" (a kind of LAURUS, the TETRANTERA
LAURFOLIA); two parts of the sap, "the juice" of a sugar-palm tree: "JAGGERING"
or BORASSUS FLABEL1FER; a fruit called "UN TCHIT" and cotton fibre ; and one spoonful
(spoon made from Cocoanut shell) of sesamum oil. After the ingredients were mixed, water
was added as the mason thought fit.
15.
The batching of the mortar was empirical too: take five parts of lime
and six of sand, dry mix, knead with a "variable" quantity of the said paste, with
a pestle moved by the foot, one hundred times for each batch.
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16.
Such a recipe seems excellent for stucco as sand plus lime minerals
turns to a whitish mortar. The mortar used is nearly as red as the bricks themselves and very water-absorbent. Further investigation will be carried out by
laboratory analysis in order to obtain an optimal definition for the batching
of the grouts to be injected.
17.
It is known that the addition of brick-dust to non-hydraulic lime
improves the hydraulic index of the binder with a few soluble salts. "Pink
Roman concrete" was obtained in this way, as the binder was fat lime.
18.
For the organic additives, see the paper by Lauren-Brook Sickels entitled
"Organics Vs Synthetics : their use as Additives in Mortars" "Mortars, cements
and grouts used in the conservation of historic buildings", Report of the Symposium
from 3 to 6 November 198], International Centre for the Study of Preservation and
the Restoration of Cultural Property (ICCROM) Rome, 1981.
19.
Unlike the lime-mortar concrete filler found in many monuments in
Western Europe, the very fine mortar used in Pagan, as said, resembles the claypuddle type. Clay-puddle mortars are also found in France, in rather "cheap"
constructions. The result is a kind of cob-work which can last for centuries
as long as it is kept dry by a roof in good condition or good coping of the
walls, and is whitewashed with lime plaster every year.
ON THE INJECTION OF GROUTS
20.
In the aforementioned ICCROM report (see above para 18), Jean Rocard,
Architect, and Alain Bouineau, Civil Engineer, related their experience in
strengthening masonry made of limestone and clay-puddle. They observed that:
grouts made with bentonite and cement fill cracks and cavities of more than 0.05 cm.
Whereas cob-work required soda silicate grouts. According to Alain Bouineau tests
made with soda silicate and/or potash silicate grouts had shown eood results.
21.
The injection of grouts is a very efficient technique but requires testing
and analysis to determine the exact type of grout or batching, the pressure to be
applied, etc. Bouineau suggested injecting cement or hydraulic-lime grouts first
and silicate grouts next. In the specific case of Pagan brick-masonry this would
have to be discussed carefully. As the mortar is fairly water-proof when wet it
would not allow cement grouts to penetrate and the silicate grouts might meet a
crustof lime or cement. It should be remembered that, in Pagan masonry, the core
of the walls is a bearing wall, not a mere "filler" and the bearing capacity is
high.
22.
Ruined monuments in Pagan showed that while even well-built facings had
crumbled, the core was often still intact. So it might be appropriate to regard
the facings as a kind of "veneer". Although some facings were found standing even
when their base had gone, this merely demonstrated the good cohesion between the
facing and the core. The veneer image seems to be a fair illustration of what
actually happened. However, facings may also become disconnected from the core,
which compromised their stability. In that case borings made for the injection of
Monuments should be kept as
dry as possible.
a) new bricks should be laid with very
thin joints and a carefully chosen
colour of mortar. A "colour-card"
of samples should be made available
to help to determine the exact
batching to be used.
b) priority should go to keeping the
structures dry. Restoration should
concern the bases and then the uppei
parts. Any water within the
structure will spoil plastered
facings both externally and
internally. Mural paintings need
special care.
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- 8 -
grouts can be used for "pinning". As a general observation, it should be
remembered that the decay of all structures starts at the base and at the top
of the walls.
23.
Originally Pagan structures were conceived as follows: plaster provided
the first protection for the wall-facings or "brick veneer", very thin joints
provided the second with a high bearing capacity and the core carried the
principal load with low-pressure stress.
RESTORATION AND REINFORCEMENT
Restoration
24.
Although the Venice Charter* states that any "restoration must be clearly
read", three aspects are essential:
the technical quality of the workmanship;
the homogeneity of the final appearance;
the discretion of the new pattern.
25.
Rational and aesthetic choices frequently conflict as aesthetics is
subjective and physical capacities are objective.
Restoration is not only Repair
26.
Cultural heritage is more than the mere gathering together of structures.
It is a legacy and a testimony of how our ancestors lived in every respect,
materially and spiritually. Cultural heritage can unite all members of a
community or a nation and restoration is a task that must be carried out with the
utmost care.
A Good Repair Job can be a Restoration or merely a Repair
27.
Restoration is a matter of feeling, tact and cultural awareness. It is
very important that all the members of a restoration team should be convinced of
the imperative need for quality and respect for the object to be restored, which
should be regarded as an important masterpiece. Those who work on restoration
programmes must therefore be dedicated to what they do and know why they do it.
If they are well trained they must pass on their know-how to trainees. This idea
is developed in the memorandum on fellowships. Good workers can turn into good
restorers if they are patient and convinced. Again, they may prefer to direct
their activities towards the contemporary construction field. No-one has the
right to judge such choices.
+
"International charter for the conservation and restoration of monuments arid
sites", International Council of Monuments and Sites (ICOMOS), Paris, 1966
- 9-
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Thin recessed joints are required and the colour should be chosen
carefully. The bricks should be clean and no mortar should be left
after the joints have been filled.
Stucco plastering and decoration can be protected by lime-grouting
and repairs.
Restoration is not only repair.
Good restorers must be patient and dedicated.
- 10 -
REPOINTING AND RESTORATION
28.
Repointing joints, treating joints in re-built sections and repairing
cracks are the most delicate parts of the mason-restorer's task. The purpose of
the work, of course, is to make the facings water-proof so as to prevent the rain
from penetrating the structure and washing away the inner mortar. Nevertheless,
repointing should be as discreet as possible and the general pattern of the facings
should be kept. As Pagan brickwork was intended to be plastered.to leave pointed
joints visible would be to alter that pattern as well as the archaeological
authenticity of the document.
29.
The training sessions carried out in the field helped to devise general
guidelines which are set out in the memorandum below. The main ideas on the
technical side are that the new mortar must be fairly weak with about half the
bearing capacity of the bricks. The mortar must be carefully pressed into the
joint, at least one inch deep (2.5 cm), and the colour should match the colour of
the bricks as far as possible. It would be better to have a slightly darker tone
to create the effect of hollow joints than one that is too light. The golden rule
must be thin recessed joints and clean bricks. The masons need buckets and pails,
clean water and brushes to remove mortar which drops on to the brick-faces and
another pail to keep their tools clean. For good results mortar should be applied
to wet bricks.
REBUILDING
30.
Rebuilding is essential around cracks or where parts are missing.
Whenever possible old bricks of the same size and colour as the surrounding bricks
should be used. An easy way to show that part of the brickwork has been rebuilt,
in walls and in vaults, is to set back the new facing about 4 to 6 mm. Again,
this is a matter of tact and subjective appreciation. On the stupa No. 1619 it
was well done. The archaeological decision "to show the scar" must be properly
explained to the masons and treated in harmony, which also depends on sensibility
or subjective judgement.
31.
The modern bricks currently used in rebuilding fit the purpose
technically, although they are of poorer quality, and their size is appropriate.
Consequently the restoration does not falsify the artistic or historic evidence.
For artistic reasons the brick-faces should be of a size close to that of the bricks
in the section to be repaired. This can be obtained in Pagan, where bricks are
still hand-made. Modern bricks are laid with thick joints because they are flat.
Concave faces could be obtained, however, if moulds were provided by the
Construction Corporation. Special care must be taken to avoid over-visible
joints. The thickness, colour and grain of the joint and its finish are all
important. Satisfactory results will be achieved only by practical tests and
training.
Each Part of a Monument has a Pattern of its Own
32.
Once again, it is all a matter of tact. The best solution would be to
use new bricks specially made for the purpose, in fairly limited series. New
bricks should be the same size as the old ones and have concave beds to
- 11 -
accommodate thin joints. They should be of better quality than the bricks
currently provided on the site. v To avoid any confusion in the future between
modern and original bricks, it would be advisable if the new bricks were
stamped with some kind of distinctive seal. The special series should also take
into account the thickness of the layers of bricks, the change in their colour,
and the differences in the joints, which can make repairs look like scars on a
face.
33.
Archaeological authenticity and good engineering designing are not
the only criteria; aesthetical considerations must always be respected in
restoration even though they are subjective.
34.
As the injection of grouts is recommended, repointing is a necessity
which cannot be avoided. The best cure is to keep the structures dry. To gain
time in the challenging task of repointing in order to make the bases and tops of
walls water-proof, a silicone treatment may also be applied. The solution of
profiled asbestos sheets might be considered too, depending on scale.
GUIDELINES OR MEMENTO ON THE INJECTION OF GROUTS
35.
In ancient structures, owing to age and moisture conditions, original
mortar loses its bearing capacity and as a result the bearing and shearing
capacities of the masonry become weaker and weaker. The homogeneity of the
structure, and the distribution of the stresses change, owing to "weak points".
While the injection of grouts is a good technique for reinforcing or strengthening
old masonry, "partial injections" should be avoided as these may create "strong
points" where the stresses may converge and bring about new changes.
36.
Injections can be carried out by gravity, at very low pressure, or at
low pressure with pumps. High pressure is very dangerous and may ruin the
masonry. Injections of grouts develop internal pressure due to:
1)
2)
3)
the pressure of the injection itself;
the hydrostatic pressure of the fluid until the binder sets;
the possible swelling of clay-puddle mortars when damp.
To avoid an excessive rise in hydrostatic pressure, inject slowly, upwards from
the base of the wall, and by horizontal "slices" at the same level. It may happen
that the injected grout will leak from the base of the wall into the ground,
through cracks or pockets in the foundations. An excessive quantity of grout
might provoke such an incident. If it occurs, stop injecting into the masonry
and inject into the soil, if possible on both sides of the foundation. Cement
grouts may be used for faster setting. Then re-inject the masonry before
proceeding upwards. Inject the ground with stabilized cement grout about half a
metre from the foundation; high pressure can be used depending on the nature of
the ground.
37.
Methodical records should be kept of grouting operations, especially in
resotration work. Scale sketches should show the position, depth and angle, of
each point of injection, each boring. Tables should give the quantities of grout
- 12 -
Repointing is very delicate and
important work.
- 13 -
injected with each boring pressure measured at the injection-pipe level, the
time taken for rejection and any other incidents.
Proposal for a model of a record card
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for the grout at the bottom of the injection pipe.
38.
Grouts should never have a higher bearing capacity than the bricks or
stones. "Weak points" should never be replaced by "strong points" where stresses
may converge and change the homogeneity of the horizontal structure of the
monument. Care should be taken to see that the cure is not worse than the disease:
the goal must be to restore the homogeneity of the original structure.
39.
The bearing capacity and porosity, or ratio of voids to the total volume
of the material of all samples as well as samples of grouts should be tested in the
laboratory prior to use. Grouts, like the mortars used to repoint the joints
should have a weaker bearing capacity and be more porous than the bricks.
40.
It should never be forgotten that there is a constant migration of the
moisture rate: over-water-proof or damp-proof grout or mortar may damage the
facings and cause alteration due to the migration of chemical salts.
41.
Another chemical reaction which may cause damage and ruin lime-plaster
coats and mural paintings occurs when cement and lime-plaster meet. There should
be no cement grout in structures decorated with ancient mural paintings. Natural
hydraulic lime-grouts should be used or hydrated lime with an addition of no more
than 107o Portland cement.
42.
Over-water-proof facades will
the inner facade with mura.l paintings.
to set. These binders will not set and
Hydraulic binders, atabilized with clay
used for grouts.
increase the migration of water towards
Both fat lime and hydrated lime need air
harden inside a wall, or only very slowly.
(bentonite) or hydrated lime should be
43.
Friction stresses are weakened by grouts which somehow lubricate the
materials. This should never be forgotten and should be carefully borne in mind
when injecting vaults, where the stresses change considerably.
- 14 -
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Wall facings were not pointed but plastered. Although
repointing is essential to keep mortar dry, it changes
the archaeological authenticity and must be extremely
carefully done. The colour and grain of the mortar can
spoil technically good repointing...
Aesthetic considerations are essential too.
- 15 -
44.
When the walls are made of two facings and a core or filler as in
Pagan monuments, such lubrification added to the different pressures can shiver
the facings and the core and "pinning" may be helpful. In some cases it becomes
a necessity. If the facings are inflated, it is advisable, before grouting the
wall, to tie the facing to the core or both facings together through the core.
Tie-rods or bar-clamps
to tie the facing and
the core of a wall
in t-
MC
"Pins" can be set into the drilled borings in the same way as tie-rods or
bar-clamps, "pig tails" or screwed bars. Cement-stabilized grouts should be
used to seal pins and tie-belts (or rods) to prevent their corrosion by rust,
which will expand and can ruin the masonry.
45.
Leaks from lime or/and cement grouts spot and stain the brick or stone
facings. The surfaces should be washed at once with clean water and brushes. If
spots dry on bricks and prove resistant to washing, a diluted acid solution should
be tried before rinsing again. Sand-blasting should be avoided, so should sanding
machines, as they may erase tool marks of archaeological importance.
On the Penetration of Grouts
46.
Hydraulic lime-grouts do not penetrate cavities or cracks less than
half-a-millimetre wide, which means, virtually, that they cannot penetrate or
impregnate old mortar. Nor can cement-stabilized grouts. Useful additives are
bentonite or teepol, preferably bentonite. Chemical grouts (potash or soda
silicates) impregnate clay-puddle mortar and can improve its bearing and shearing
capacities. But it may happen that chemical salts come to the face of the wall.
Weak sand-blasting can erase such deposits, but the bricks of Pagan monuments are
so soft that it would be advisable to clean them by hand with brushes. In Pagan,
should the temptation of sand-blasting be too strong to be resisted, "restorers"
should proceed on very dry surfaces only. It is not to be recommended.
47.
Joints should be pointed at least three days before the injections are
made; a week would be better to allow the binder of the mortar to set, especially
if it contains lime.
MEMENTO ON POINTING
48.
Beyond the technical importance of pointing the joints, attention should
be drawn to the aesthetical and archaeological importance of the brick walls
which were not pointed in Pagan. Choosing and gauging the mortar is therefore
very delicate. Technically, the mortar should be less damp-proof than the bricks
and have a weaker bearing capacity, as with grouts. On the aesthetical side, an
- 16 -
initial experiment was carried out to define typical mortars as a colour card
for painters. The aim was to obtain a colour range with fairly standardized
samples of mortar, so that colour and grain can be chosen from dry samples, for
mortars turn whitish when dry. Different mortar-mixes have been tested, with
white lime, grey Portland cement, red-brick dust or "sulky" clay and sand.
Samples should be taken systematically and kept to permit a choice between each
colour and grain, whether rough or glossy.
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49,
Mortars can be made with several binders. In Pagan in August 1986 only
hydrated lime and Portland cement were used. Compression tests were to be made
subsequently.
50,
Binders. Since grouts are injected into the walls, no air can help aircured binders to set. Hydraulic lime grouts are required but with minimal
quantities of cement. Air-cured binders are excellent for the mortar used in
repointing. Fat lime gives the best results and is easy to work.
51,
Joints: The joints of much of Pagan brickwork are so thin that one
cannot even stick a needle into them. This is due to the concavity of the lower
bed of the bricks. To point such joints an old saw-blade should be used to lever
If, for structural reasons, these perfect faces have to be grouted, this should be
attempted before repointing. Quite possibly the grout will not leak, but pointing
is necessary to keep the masonry dry. Tests can also be made with clay in order
to inject grouts behind the facings, at low pressure. In this way the ancient
pattern of the outer facings would be kept. Consequently, different techniques
must be tried on different monuments, and practical, physical tests are a very
important part of the restorer's work. To keep the structures damp-proof, the
joints of the upper and outer facings must be pointed regardless of the
strengthening solution ultimately chosen.
Where the internal facings of temples,
walls, pillars and vaults are concerned, if no grouts are to be injected, the
a) brick masonry in Pagan was protected and decorated by a coating
of stucco.
b) infiltrations from the upper parts
wash away the inner mortar, ruin
the brickwork and cause the
plaster to flake off.
c) upper parts and bases are more
severely damaged by humidity than
the middle.
d) the facings in the original brickwork were not pointed.
e) although the appearance of a ruin
may be kept, water must not
penetrate the masonry.
f) thin recessed joints of a chosen
colour would look better even with
modern bricks.
The best cure
is to keep the
structures dry.
- 18 -
joints should not be pointed.
This will let the masonry "breathe".
ON REINFORCED CONCRETE PROTHESIS
52.
Three kinds of prothesis are suggested and even designed:
1) Tie-belts and posts of reinforced concrete set in masonry.
2) Steel ties.
3) Jackets of reinforced concrete, "cement gunnite" as a coating
for pillars or walls.
The purpose of these techniques is to improve the shearing capacity of brickmasonry structures. For the upper parts, the Sikkara and the decorations,
rigidity may be helpful, but in the event of an earthquake, the rigid pieces
might be disrupted from the main body. The idea of a reinforced concrete frame
inside a reconstructed Sikkara is not inacceptable, depending on the skill of
the designers and masons.
53.
Design must be planned on the spot, in a "team approach" by the
designer and the archaeologists and the performers who will have to execute the
work physically. It should be borne in mind that reinforced concrete has the
same coefficient of thermal expansion as iron. The prothesis, therefore, should
not be more than twelve or fifteen metres long. The embedding of steel bars in
concrete is never less than three centimetres thick. A cement binder should be
used for the grout injected round the steel bars to protect the bars from corrosion.
Applying reinforced concrete belts and posts is very delicate. They should not
create "strong" or over-rigid zones that will upset the homogeneity of the
structure.
54.
Reinforcement should be as flexible as possible. Diffusion of
stresses is better than concentration. Moreover, reinforced concrete prothèses
should also be inserted in masonry for aesthetic reasons, not only to avoid
thermal shocks. The facing of the wall covering the reinforced concrete belts
and posts should be built with original bricks carefully set aside for re-use in
the same place.
55.
Jackets are not to be recommended for aesthetic and archaeological
reasons. The pillars are very often adorned with paintings, niches and steatues;
an architectural finishing of the surfaces that will comply with the style of
the monument is a Utopia. What is more, the thickness of jackets would change
the proportions of the pillars as well as the proportions of the corridors and
the doors. Again restoration is not only repair: it is repair and more than
repair. Cultural heritage is a far greater thing than a gathering together of
structures: it is one of the material and spiritual links where a nation finds
its roots. The work must be carried out with constant respect for the monuments.
The masons, engineers, and architects involved in restoration are the keepers of
a tradition of "know-how" in building activities and are responsible for such
maintenance. Structural engineers should look for a concept for strengthening
pillars with ties instead of jackets.
- 19 -
56.
Ties : Ties are necessary to improve the shearing capacity of some
structures. Extreme rigidity is not required and some flexibility is compatible
with the homogeneous structures dealt with here. It is better to have many tierods than one rigid reinforced concrete belt.
MEMENTO ON BRICKS
57.
Porosity: Although the old bricks of Pagan are of very good quality,
they are porous. For centuries they were covered and protected by excellent limeplaster stucco which may have contained organic additives. Some remains of this
protection show that at one time the stupas and temples were white. But the
beauty of the half-ruined red monuments is so intense that no one will agree to
whitewash or plaster them for suitable protection against moisture. Recent
studies on stone conservation in Western Europe have revealed that whitewashing
proved an excellent practice for that purpose as well as for decoration. In
Italy people even washed stones with vegetable oil.
58.
A modern water repellent is silicone. Tests should be made in Pagan,
although silicone usually loses its effect after about twelve years, according
to evidence in France. It might be advisable to make the upper walls and bases
water-proof by using silicone as a temporary protection while the repointing and
eventual injection of grouts are being done. Modern bricks in Pagan are more
porous because they are made of sandy clay and burnt at a low temperature. Even
if better-adapted sizes and shapes can be obtained, there should be an improvement
in quality, otherwise the new bricks may not last as long as the old ones.
59.
Where bricklaying is concerned, practical training must be provided to
show the masons how to make thinner joints. They will have to use wet bricks
so the bricks should be placed in water at night if they are to be used the next
day. This will prevent them from absorbing the water in the mortar.
ON MAINTENANCE AND REPAIR
60.
Equipment such as generators, compressors, drills etc., are resistant
but need regular maintenance, both routine and planned. A dust-free workshop
with brick flooring, a bench and proper fittings to keep tools and spare parts
in very strict order is essential.
To Sum Up:
61.
On grouts: use no cement where there are paintings or lime-plaster.
Bearing capacity tests should be made in the Mandalay laboratory under
the supervision of the director;
Grouts: as above, using the colour card to choose the batching from
dry samples.
On records: before proceeding, take photographs and label; make sketches;
plan the work; talk to the archaeologists; record grouting operations;
and the choice of mortar for the joints.
- 20 -
On safety: Scaffolding - check that the sole-plates are placed
horizontally under the posts; the posts are vertical; the horizontals
are fixed to the posts and not to the horizontals; there are diagonal
braces to brace the wind in both directions; no plank protrudes by
more than one foot, a cantilever means an accident; ladders, toe-boards
and guard-rails are to be installed. Hard hats should be provided.
On electricity: water-proof mains; armoured cables and circuitbreakers (differential) of not more than 30mA for each phase; earth
cable and earth connexion.
62.
Slow and careful work goes farther and will produce better results
than a rush fellowship. Trainees wishing to become junior engineers would
achieve more by practical and theoretical experience (six or eight months)
with contractors and restoration architects, than by long periods in universities
or offices.
CONCLUSION
63.
The conclusion, after a first stay in Pagan, is that steady efforts
and re-organization will be necessary in order to render Pagan monuments dampproof and to maintain them. This might be called "conservation". Before any
work is carried out, however, there must also be a concertation of the archaeological officers and architects of the Department of Archaeology and the engineers
and architects of the Construction Corporation. It should be borne in mind that
the heritage to be preserved is a Burmese heritage and also the heritage of mankind.
It is such a challenge that only a team can win. Once again, it must be
remembered that the cure cannot be worse than the disease.