View
3
Download
0
Category
Preview:
Citation preview
DIAGNOSIS OF BUILDING FAILURES
IN POROUS MATERIALS
Dr Donald Ellsmore
Director, Donald Ellsmore Pty Ltd
Convenor, Australasia Chapter
Association for Preservation Technology
The predominant materials of the built
form of the World Heritage listed sites
of Melaka and George Town Penang,
and many other parts of Asia, are
porous.
Porous materials are stone, bricks,
plasters, wood, clay roofing tiles,
ceramic tiles and some decorative
finishes.
2
All porous materials are affected in
one way or another by water, which
is often an agent of decay.
Water dissolves and washes away
surfaces, it causes wood to expand
and it causes salts to move around
in masonry materials. It is essential
for living organisms, including
vegetation and mould.
3
Water is a dangerous enemy of poorly maintained buildings.
4
In well maintained buildings water is managed for the benefit of the occupants
and the fabric of the buildings.
5
MAKING DECISIONS ABOUT BUILDINGS
• Understand the significance of the building and place –
understand what is most important about it and what should be
conserved.
• Protect authenticity – ensure that all actions are based on an
understanding of authenticity.
• Take all necessary steps to address the issues of greatest
concern – secure the fabric, ensure that use is appropriate for
the place and do not remove significant material or introduce
incompatible new material unless there is no alternative.
• Undertake appropriate maintenance and avoid damage.
6
When MAKING DECISIONS about HERITAGE BUILDINGS
several important matters must be considered.
Significance is a function of history, authenticity, social and community esteem.
7
The inscription of places on the World
Heritage List is based on Universal
Significance – a concept which
embraces tangible and intangible
values.
Tangible values include building
fabric, which should always maintain
its authenticity in order to preserve its
inherent values.
8
The ways of doing things in SE
Asia often differs from Western
ways.
Heritage practice in the East is now
guided by principles that derive
largely from Western practice
though recognising Eastern values
that are inherent in and fundamental
to significance and authenticity of
heritage places.
9
In Western society a concern for the
conservation the authentic fabric of
ancient buildings was raised in the
19th Century by William Morris,
John Ruskin and others. They
established the Society for the
Protection of Ancient Buildings
(SPAB) known as ‘Anti-Scrape’
because of its opposition to
aggressive restoration. The SPAB
approach informs or modern
practices.
10
The Australia ICOMOS
Charter for Places on
Cultural Significance,
1979 (revised 1999) –
developed from the Venice
Charter , 1964.
Principles for the
Conservation of Heritage
Sites in China, 2000.
Hoi An Protocols for Best
Conservation Practice in
ASIA, 2009.
11
In the South East Asian context
authenticity can have a different meaning
from the Western concept.
It may involve continuing customs and
practices.
12
Authenticity of intangible traditions
does not preclude the use in
conservation of traditional
technologies or new science. Both
may be applied to obtain good
outcomes.
13
WHY CONSERVE AUTHENTIC FABRIC?
Authentic fabric is physical evidence of history – it provides access to truth.
14
Authentic fabric can provide a window through which to view history.
15
16
In SE Asia there are many pressures
on heritage places. There is
pressure to obtain economic
benefits, accommodate tourists,
maintain social cohesion and also to
protect places of value to local
communities and to the World
community.
There are issues that are common to
many places.
17
18
Tourism impacts on conservation.
Tourism impacts on clarity of
purpose?
Tourists can overwhelm heritage
places?
19
Good conservation outcomes can be
obtained with careful planning and
the application of heritage
guidelines.
20
Poor conservation outcomes arise
through neglect and lack of
attention to basic maintenance or
through the application of
inappropriate methods and
materials.
21
When it comes to undertaking
heritage works, the important
matters are protection of
significance and authenticity, and
the use of appropriate methods and
materials, based on a correct
understanding of materials
properties.
22
It is tempting to suggest that a good
coat of impervious paint will solve all
problems with porous buildings but the
reality is somewhat different. In fact it
is found that the use of non-porous
paints will often hasten the decay of
traditional buildings made of porous
materials. The care of heritage
buildings requires a clear
understanding of their significance and
their conservation needs.
23
Technologies for fabric
conservation are expanding with
scientific research and by drawing
from continuing traditional
pactices.
24
25
Traditional practices are often the best for use in SE Asian countries.
26
In other places the loss of traditional skills causes a greater focus on new technologies.
BRICKS AND MORTAR
27
Brickwork is normally made with
moderately hard bricks laid in
relatively soft mortar. The role of the
mortar is to bed the bricks and
distribute the loads. It is NOT to stick
the bricks together.
Brickwork deteriorates when it is
exposed to salts and damp and when
hard mortars are used with soft bricks.
28
PLASTERS
29
Traditional plasters are made with
sand and lime and applied in layers.
The top surface layer is usually harder
and smoother than the underlying
layers. Its purpose is to protect and
decorate.
Plasters should not be allowed to
remain damp or they will deteriorate
due to salt activity and fungal decay.
30
In SE Asia there are many fine
examples of stucco illustrating early
cultures including Kmer culture. There
is little difference between the ancient
plasters and those used in more recent
times prior to the introduction of
Portland cement. Modern cement
plasters are different to traditional
plasters and incompatible with soft
bricks and stone.
31
Traditional lime plasters should not be replaced with modern Portland cement.
32
WOOD
33
Wood is a hygroscopic material that
expands when the moisture content
increases, and shrinks when the moisture
content decreases.
Changes in atmospheric moisture content
is one of the principal causes of
deterioration of wood.
The other causes of deterioration are
weathering, or the combined effects of
water and sunlight, and biological decay
in the form on insect attack and fungal
decay.
The constant expansion and
contraction of wood, with changes in
relative humidity, causes the failures
including coating failures, splitting and
in some instances collapse of wooden
structures.
Exposure of wood to sunlight causes
wood to weather and, ultimately, to
deteriorate.
34
Fungal decay in wood.
35
CONCRETE, IRON AND STEEL
36
Most concrete is
reinforced with iron or
steel.
Reinforced concrete is
now used in most large
new structures,
Iron and steel corrode
when exposed to water
and air.
Concrete is relatively
stable but it readily
deteriorates when steel
reinforcement corrodes.
37
Causes of concrete deterioration
include:
• Aggregate expansion
• Corrosion of steel reinforcement
• Chemical damage
• Carbonation
• Chlorides
• Sulphates
• Leaching
• Decalcification
• Sea water
• Bacterial corrosion
• Thermal damage
• Radiation damage
• Physical damage
• Human intervention
The rapid growth of urban centres ,
particularly in S E Asia, has
brought about a looming crisis with
reinforced concrete structures
38
Concrete failure due to corrosion
Concrete surface failure – man made
Concrete failure due to delamination of steel
Concrete surface failure - natural
39
Reaction between alkali and aggregate – is just one form of failure with serious
consequences for some concrete structures.
40
PAINTS AND FINISHES
41
Villa in Phra Nakhon, Bangkok Old Shophouse in Tha Pae, Chiang
Mai
42
Traditional yellow colouring on
French colonial villa in Champasak,
Laos
Traditional yellow colouring on
stucco of French colonial era
temple in Champasak, Laos
43
Modern yellow colouring on 1930s
concrete History Museum in Hanoi
designed by Hebrard
Modern interpretation of traditional yellow
colouring in George Town, Penang
44
The traditional yellow colouring which
has been used for centuries is inexpensive
and simple to make and easy to apply. It
lasts longer than modern coatings and is
far better for the conservation of porous
masonry structures
45
LEARNING AND DOING
46
47
The next generation will benefit from the proper care of our heritage places.
48
Recommended