Bachelor of Engineering Thesis
Viability of Bamboo Reinforced Concrete for
Residential Housing in Indonesia
By
Timothy Clancy Fergusson-Calwell
2015
Supervisors
Rob Wolff
School of Engineering and Information Technology
Charles Darwin University
Sabaratnam Prathapan
School of Engineering and Information Technology
Charles Darwin University
School of Engineering and Information Technology
Abstract
Reinforced concrete is arguably the most common building material in the world; however the
reinforcement used is steel which is expensive and can be hard to acquire in third world countries.
An alternative cheaper reinforcement material with a high tensile strength is bamboo.
Extensive research through already available literature on bamboo replacing steel as a
reinforcement material in concrete has been conducted. The research was considered and analysed,
establishing clear conclusions that bamboo can in fact be used as reinforcement in a residential
concrete house.
Factors such as tensile strength, availability of bamboo, design calculations, and costing have all
been considered and lead to theoretical viability of bamboo reinforced concrete. However water
absorption is an unfavourable inherent material limitation, which needs to be treated before being
used as a structural material, procedural methods for this treatment have been devised and will be
further tested. The effectiveness of these treatments have been further analysed and discussed,
with a conclusion stating bamboo is in fact a viable replacement for steel, however further research
must still be performed.
Contents
1.
Introduction .................................................................................................................................... 5
2.
Scope ............................................................................................................................................... 6
3.
Literature review............................................................................................................................. 7
3.1.
Concrete .................................................................................................................................. 7
3.1.1.
Overview ......................................................................................................................... 7
3.1.2.
Reinforced concrete ........................................................................................................ 7
3.1.3.
Sustainability of reinforced concrete .............................................................................. 7
3.2.
Bamboo ................................................................................................................................... 9
3.2.1.
Overview ......................................................................................................................... 9
3.2.2.
Limitations..................................................................................................................... 10
3.2.3.
Mechanical properties of bamboo................................................................................ 11
3.2.4.
Selection, Preparations, and Storage ............................................................................ 12
3.3.
Indonesia ............................................................................................................................... 14
3.3.1.
Local bamboo ................................................................................................................ 14
3.3.2.
Common housing examples .......................................................................................... 14
3.3.3.
Extreme weather condition effects .............................................................................. 14
3.3.4.
Industry and by-products .............................................................................................. 15
3.4.
Bamboo Reinforced Concrete ............................................................................................... 16
3.4.1.
4.
5.
Bonding issues............................................................................................................... 16
Design principles ........................................................................................................................... 18
4.1.
Theoretical Viability .............................................................................................................. 18
4.2.
Treatment Considerations .................................................................................................... 18
4.2.1.
Bituminous Paint ........................................................................................................... 18
4.2.2.
Paraffin wax with helical copper wire ........................................................................... 19
4.2.3.
Epoxy with fine sand ..................................................................................................... 19
4.2.4.
Topography manipulation............................................................................................. 19
4.2.5.
Controlled ..................................................................................................................... 19
4.3.
Concrete mix ratio................................................................................................................. 19
4.4.
House design and load bearing ............................................................................................. 19
Cost analysis .................................................................................................................................. 20
5.1.
Availability of bamboo vs. steel ............................................................................................ 20
5.2.
Labour intensity .................................................................................................................... 20
5.3.
Raw materials........................................................................................................................ 20
5.3.1.
Steel Rebar .................................................................................................................... 20
5.3.2.
Bamboo Poles ............................................................................................................... 21
5.3.3.
Treatment materials ..................................................................................................... 21
5.4.
6.
7.
8.
Final cost presumptions ........................................................................................................ 21
5.4.1.
Total cost per 100m comparison .................................................................................. 22
5.4.2.
Cost analysis conclusions .............................................................................................. 22
Laboratory Testing ........................................................................................................................ 23
6.1.
Tensile test ............................................................................................................................ 24
6.2.
Moisture content testing ...................................................................................................... 27
6.3.
Water Saturation Testing ...................................................................................................... 28
6.4.
Pull out test ........................................................................................................................... 29
6.5.
Discussion.............................................................................................................................. 36
Conclusion and Future Work ........................................................................................................ 38
7.1.
Conclusions ........................................................................................................................... 38
7.2.
Future Work .......................................................................................................................... 40
References .................................................................................................................................... 41
Appendices............................................................................................................................................ 44
Appendix I – Results and Calculations .............................................................................................. 44
Cost analysis calculations .............................................................................................................. 44
Theoretical bamboo substitution calculations ............................................................................. 46
Tensile Test Results ....................................................................................................................... 48
Water Saturation Results .............................................................................................................. 48
Pull-out Test Results...................................................................................................................... 49
Appendix II ........................................................................................................................................ 51
1. Introduction
Reinforced concrete is arguably the most common building material in the world. It is highly
industrialised and can be found almost anywhere in the populated world. Concrete structures are so
sustainable they have been replacing even the cheapest construction materials around the world,
including mud and brick houses. Materials and methods to create concrete are very cheap and
economical, however the concrete is most commonly reinforced with steel, which is quite expensive
and often unattainable, in particular to the third world.
Cheaper materials and manufacturing processes which will require less energy are being
investigated, and the attention of researchers and industries have started to fix onto materials such
as vegetal fibres including soil, industry waste, and plant life, due to their sustainability, recyclability,
renewability and lack of heavy costs. However due to the education system in developing countries
being moulded by the programs of industrialised nations, little formal education and research
programs are existing which concern traditional and locally available materials and technologies.
This lack of reliable and technical information about local materials tends to mean that consumers
will mainly use materials with technical information freely available, i.e. already industrialised
materials, which could mean that cheaper alternative materials are being overlooked. A prime
example to this lack of research is for local Indonesian bamboo, which is already in use for many
temporary measures but could perhaps be put to use permanently as reinforcement within concrete
structures.
The focus henceforth is to provide a concise and detailed summary of bamboo as a reinforcement
material in concrete for residential style housing, in Indonesia. Cost is a crucial consideration in
housing design for the poor; therefore attempts to develop a method for bamboo to replace steel
must be cheap, viable and sustainable. This substitution will be actioned in key structural elements
(slabs, walls, columns and beams) of a modest domestic home. Costs must be drastically reduced
however factors such as safety and durability must not be heavily compromised. This process could
ultimately make safer housing much more affordable for the local lower to middle-class Indonesian
resident.
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2. Scope
The objective of this thesis was to test the effect of bamboo as replacement for steel as the
reinforcement in structural concrete, for residential housing in Indonesia.
This was done by analysing and comparing the characteristics of local Indonesian bamboo against
steel whilst performing tests on bamboo where appropriate. The analysis consists of mechanical
tests along with a literature review of previous studies, and the results of the thesis helped
determine the viability of bamboo as a cheap and renewable non-steel reinforcement within
concrete.
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3. Literature review
3.1.
Concrete
3.1.1. Overview
Concrete is a composite material comprised of water, fine and coarse granular aggregates, all
embedded in a rigid medium of cement, which mixes with the water and fills voids among the other
materials and glues them together. Concrete is one of the most durable construction materials on
the planet. It has extremely high compressive strength and provides a superior fire resistance when
compared to other construction materials such as timber or steel.
Concrete is also a very sustainable building practice, having; low waste, low inherent energy
requirements, using some of the most abundant resources on earth, high thermal mass, high service
life, and able to be made with recycled materials.
3.1.2. Reinforced concrete
Concrete has a low tensile strength and ductility, to counteract these properties, reinforcement is
used within the concrete and it becomes a composite. The reinforcement used is most commonly
steel, called ‘rebar’, however steel does not necessarily have to be the reinforcing material. The
reinforcing bars are fixed flaccidly into the concrete before the concrete sets. The most common
practice of reinforcement is to resist tensile stresses, in which case could normally cause
unacceptable cracking or structural failure. Concrete is often in a permanently stressed state
(compression), and to improve performance of the structure whilst under working loads a method
called pre-stressing can be used, such as pre-tensioning. Strong, durable reinforced concrete has
properties including; high relative strength, high toleration of tensile strain, good bond to the
concrete regardless of moisture and pH levels, high thermal compatibility.
3.1.3. Sustainability of reinforced concrete
In comparison to other construction materials, reinforced concrete has a highly diverse amount of
sustainability attributes when compared to materials such as mortar, brick, timber, non-reinforced
concrete, etc.
3.1.3.1.
Environmental
Concrete has a low amount of waste, with components frequently cast with specifics. Recycling can
be done to the little excess that is produced, via cut-outs etc. Enhanced energy efficiency comes
from reduced HVAC costs. Heat is absorbed throughout the day and released at night via concrete’s
inherent thermal mass. Significant amounts of cement can be replaced with industrial by-products
such as blast-furnace slag and silica fume, removing them from landfills.
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3.1.3.2.
Economical
Reinforced concrete has a high level of durability, therefore increasing its service life. Structural and
aesthetic purposes are retained for many decades. Due to this long-term durability, the need of
extensive maintenance is minimized. Due to concretes monolithic approach to design, little to no
joints need to be maintained.
Due to the simplicity of concrete fabrication, it can be made almost anywhere in the world.
Transportation costs can therefore be reduced by using local materials.
3.1.3.3.
Social
Concrete creates safe, secure and comfortable designs whilst providing a high fire resistance along
with low noise transition. Reinforced concrete buildings have the capability to withstand natural
disasters which diminishes disastrous destruction and need for repair/replacement.
Some other factors concrete possess include design flexibility, aesthetic variety and reduced floor
heights in multi-story structures.
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3.2.
Bamboo
3.2.1. Overview
Bamboo is predominantly a variety of giant grass with woody stems. There are two consisting parts
of a bamboo plant, the rhizome which bears the roots and is located underground, and the stem
which grows above ground. When the plant is young the stems are called “shoots”, and when the
plant matures they are called “culms”. It is one of the fastest growing plants in the world with
growth rates reported to be as high as 250cm in 24 hours, however the growth rate does depend on
species, climatic conditions and soil conditions. A typical growth rate, in temperate climates, is 310cm in 24 hours during its growth phase (Panda, 2011). Bamboo plants are distributed into either
runners or clumps. Runners grow in a haphazard fashion and clumps will add new shoots around a
primary culm which grows clump size radially. One clump will produce approximately 15 kilometres
of useable culm in its lifetime (Panda, 2011).
There are over 1000 species of bamboo, and can be found in very diverse climates ranging from
tropics to mountains. Native growth and distribution is as far north as 50oN and as far south as 47oS
which ranges through South East Asia and India, Central Africa and South America. Bamboo can be
grown in almost any soil and can be full size within 12 months provided it is fed well with mulch and
fertilizer (Roach, M. 1996). The root systems of bamboo range from only 30-50cm in depth,
therefore having minimal long term impact on its surrounding environment (Bambooland.com.au,
2014). Along with its extensive accessibility, bamboo has been tested to have an ultimate tensile
strength of approximately 125MPa, which is quite impressive considering it is a natural fibre (Rottke,
E. 2002).
There are many uses of Bamboo, the most common uses include: culinary, medical, paper,
instruments, and construction. Bamboo has been used in modern construction for years, however
often only used for temporary uses such as scaffolding, as bamboo is a natural fibre and is relatively
susceptible to deterioration. New research suggests that if bamboo is chemically, physically and/or
thermally treated, it can suitably replace timber, steel, and other materials in a more permanent
setting such as bridges and housing. Industrially treated bamboo has shown suitability for use within
a composite and has already been successfully utilized for structural and non-structural applications
in construction (Johnson, S. 2010).
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3.2.2. Limitations
Mainstream recognition as a material resource has not yet been widely given to bamboo. Around
the globe, the majority of bamboo is harvested from wild environments, and many bamboo
resources have been overexploited and poorly managed. However the main attributing factor
towards the negative view on bamboo for permanent constructions would be its lack of durability
being a natural material. It is very susceptible to attack by both insects and fungi and its service life
can be as low as 12 months outside sheltering. There are many known treatment methods which
resolve bamboo’s durability limitation, it is water absorption and bonding strength which are the
main concerns when implementing bamboo reinforcement into concrete.
3.2.2.1.
Durability
Bamboo durability heavily depends on the preservation treatment methods. These preservation
methods include smoking, heating, drying, coating with limestone (calcium hydroxide) and more
recently, in addition with these methods, a chemical treatment is applied. The chemical composition
used should have no effect on the bamboo fibre once injected, and should not be washed away by
rain or humidity. No matter the treatments used, drying is a critical process in bamboo conservation.
Bamboo with lower moisture content is much less prone to mould and insect attacks, ideally
moisture content would be below 15%. The most common and effective preservation methods used
globally is drying and then chemical treatment of the bamboo.
3.2.2.2.
Water Absorption
Bamboo has a great capacity to absorb water, so much so that a dimensional variation of up to 20%
was found after a 7 day immersion in fresh water. A decrease in mechanical properties after this
same water absorption was also apparent, due to the development of hydrogen bonding between
the cellulose fibre and water molecules (Che Muda and Sharif, 2013). According to Che Muda and
Sharif, on average tensile strengths recorded a 30% drop, flexural strengths had a 23% drop, and
impact strength experienced a 32% drop. As can be seen from the findings of this previous study, it is
imperative to implement some form of water repellent when using bamboo in a permanent,
structural manner.
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3.2.3. Mechanical properties of bamboo
The material properties of bamboo, as shown below in table 1, gives a good theoretical base for
assumptions and initial calculations as to determine the viability of bamboo for reinforcing concrete.
These properties have been determined by E. Brink and J. Rush, in the U.S. Naval Civil Engineering
laboratory in 1966.
Table 1 – Mechanical properties of bamboo
3.2.3.1.
Mechanical Property
Value
Ultimate compressive strength
55.0 MPa
Allowable compressive stress
27.6 MPa
Ultimate tensile strength
124.1 MPa
Allowable tensile stress
27.6 MPa
Allowable bond stress
344.0 KPa
Modulus of elasticity
17.2 GPa
Elasticity
Due to bamboo’s high level of elasticity, it makes for a very decent building material in earthquake
prone areas. Indonesia as is commonly known, frequently experiences earthquakes which often
damage constructions beyond repair, particularly due to their low elasticity and lateral
reinforcement (Shaw, A. 2012).
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3.2.4. Selection, Preparations, and Storage
3.2.4.1.
Selection and Harvesting
When selecting bamboo culms, the following factors need to be considered as they have a
significant effect on the bamboo’s properties: Do not use bamboo harvested in spring or early
summer, or green unseasoned bamboo, the fibres in these culms generally have increased moisture
content, making them weaker (Johnson, S. 2010). Select the largest diameter culms available, this is
a sign of plant maturity and higher fibre density and strength. Use bamboo of a distinct brown
colour, this warrants the plant is a minimum of three years old (Godbole, V. 1986). As bamboo is a
plant, it goes through a photosynthesis process and during the height of the day this process peaks.
This means that the highest daily level of sap will be present with the sun, therefore making dawn,
dusk, or night the ideal times to harvest (Terra Bamboo, 2014).
3.2.4.2.
Preparation
Sizing
When using bamboo as reinforcement, splints are preferable over whole culms. This is due to the
size of a whole culm and also considering culms are hollow, therefore possessing a higher buckling
failure, which could be possible after load is applied to the concrete, or even due to the self-weight
of the concrete.
Seasoning
After Bamboo is cut, it needs to be dried, seasoned and leached prior to use. This seasoning process
will last two to four weeks, and culms must have regularly spaced support to minimalize warping
(Johnson, S. 2010). Leaching is the removal of sap after harvest, and is done via postharvest
photosynthesis or with force from mechanical treatments. These practices include; pumping water
through freshly cut culms, forcing sap out; immersing culms in running steam; and placing the base
of the culms in water which will leach out the sap and also allow for full consumption of sugars by
the bamboo. Bamboo should be dried slowly and evenly, in the shade. This will avoid the cracking of
external skin membrane, and therefore reduce opportunities for fungal and pest infestations.
Bending
Bamboo can be permanently bent and shaped if heat and pressure is applied (Johnson, S. 2010). This
technique can be used to form the bamboo into ties, stirrups, and to put hooks or pegs into the
bamboo for additional anchorage in the concrete.
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Water-proof coatings
As discussed earlier, bamboo has a high water absorption capacity, and with this added water comes
a decrease in mechanical strength due to excess hydrogen bonding between water molecules and
the cellulose fibre of the bamboo. A water proof coating then becomes apparent and essential, if
bamboo is to be used as a structural material. There are many water replant coatings which can be
considered, such as coal tar, bituminous paint, sodium silicate, epoxy, the list goes on.
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3.3.
Indonesia
3.3.1. Local bamboo
Bamboo flourishes naturally in Indonesia. It is a native plant and its useful properties have been
known for centuries. There are many species native to Indonesia, but the species being considered
shall be Bambusa Blumeana, which is both the tallest and thickest growing bamboo in Indonesia,
growing up to 18 meters tall and 300 millimetres in diameter (Clayton, 2014). This species is already
used for building materials and baskets, and the shoots are eaten. Bambusa Blumeana is scarcely
researched and specific mechanical properties such as tensile and compressive strength are
unknown, along with elastic modulus and even water moisture content capability.
3.3.2. Common housing examples
Traditionally Indonesia used timber housing on stilts as can be seen below in figure 1. But
throughout the 19th and 20th centuries, brick (figure 2) and cement block (figure 3) masonry were
more commonly practiced. It is uncommon for either brick or cement block housing to have
reinforcement of any kind.
Figure 1 (left): ‘Mentawai’ a traditional Indonesian house, Figure 2 (centre): Brick masonry,
Figure 3 (right): Cement block masonry
Image source figure 1: Pelangi Senja - http://panchesatoko.blogspot.com.au/
Image source figure 2 & 3: Earth Odyssey - http://earthodyssey.net/2007/09/indonesia/
3.3.3. Extreme weather condition effects
Indonesia experiences hundreds of earthquakes per year, and cyclones are common due to its
monsoonal climate. On average around 3 earthquakes over magnitude 6 directly hit Indonesia per
year, and roughly 1-2 category 5 cyclones pass through every decade (USGS, 2014). These extreme
weather events wreak havoc on Indonesia’s homes, and often take lives. Recently in 2013, the Aceh
earthquake struck north Sumatra, having a magnitude of 6.1. Almost 16,000 homes were damaged
or destroyed, and 35 lives were lost with 276 being injured (The Jakarta Post, 2013). It was further
noted that approximately 85% of the houses that were damaged, were either brick or cement
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masonry lacking structural reinforcement, or timber stilted homes, with the majority of reinforcedconcrete housing in the area remaining undamaged (BNPB, 2013), proving that reinforcing the
housing will actually provide safer and more sustainable living conditions.
3.3.4. Industry and by-products
3.3.4.1.
Petroleum
The oil and gas industry contributes massively to the Indonesian economy. Hydrocarbon reserves in
Indonesia’s tertiary sedimentary basins are currently at 164.9 trillion cubic feet of gas, and 8.4 billion
barrels of oil (IPA, 2014). This information shows that there is still a large future ahead of the
Indonesian petroleum industry, and therefore if a water-resistant product were to be derived from
the use of petroleum this would be both innovative and cost effective. Paraffin wax is such a
product, which is actually created with a by-product from the refining of lubricating oil. Therefore if
paraffin wax could be exploited as a water repellent treatment for bamboo, this would be majorly
economic and environmental as this by-product material is being recycled. However due to wax
being smooth and having low adhesion, techniques to manipulate the topography of the bamboo
will need to be used as extra adhesive methods. These ideas include adding ribs into the bamboo, or
adding a sandy granular substance into the wax.
3.3.4.2.
Coal
Indonesia also has an enormous coal industry, being the world’s top thermal coal producer and
exporter. Coal production in Indonesia is mostly bituminous and sub-bituminous (Worldcoal.org,
2014). Yet another sustainable by-product from the energy industry can be utilised as an impervious
product for bamboo, bitumen. Considering 85% of Indonesia’s coal is at least sub-bituminous
(Worldcoal.org, 2014), this makes for a great amount of bitumen by-product and would therefore be
a viable and sustainable option as a form of water repellent coating for bamboo. A possible option
would be bituminous paint. It is water based, cheap to manufacture, has high adhesion and is
already commonly used as a waterproofing agent.
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3.4.
Bamboo Reinforced Concrete
The above sections of the literature review provide sufficient background information
demonstrating the viability and sustainability of using bamboo as reinforcement material in
residential concrete housing. However, there is still the issue of water absorption, which effects
bonding, to overcome before confirming this viability.
3.4.1. Bonding issues
3.4.1.1.
Water absorption
As discussed earlier, bamboo has a high capacity for water absorption. When bamboo fibres are
saturated their mechanical properties are dramatically reduced. Along with this mechanical
reduction there is a dimensional variation due to water absorption which, if untreated, can cause
micro cracks during the curing of the concrete, shown in figure 4 below.
Figure 4: Behaviour of Untreated Segment Bamboo as Reinforcement in Concrete (a) Bamboo in
Fresh Concrete, (b) Bamboo during Curing of Concrete and (c) Bamboo after Concrete has Cured.
Image source: International Journal of Scientific & Engineering Research - http://www.ijser.org
Factors which affect bonding, due to water absorption are; adhesive properties of cement
environment; surface friction compression on bamboo due to concrete shrinkage; and shear
resistance of the concrete, via roughness of reinforcement bar and surface form.
Slippage of a reinforcement bar in concrete is prevented by adhesion or a bond between the
materials. Dimensional changes due to (moisture content/water absorption) influence all three of
the above mentioned bonding characteristics, quite brutally. Whilst moulding and curing concrete
the bamboo reinforcement will absorb water from the concrete mix, leading to swelling. Towards
the completion of the curing period, the bamboo will lose its moisture and shrink back to its original
dimensions, therefore leaving voids around itself and resulting in cracking of the concrete (Che
Muda and Sharif, 2013).
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This issue creates severe limitations to the usage of bamboo as a replacement to steel, for concrete
reinforcement. Therefore an effective water-repellent treatment must be executed in order to
improve the bond of bamboo and concrete.
This water-repellent or impervious treatment shall be affected by four defining factors:
1. Topography of bamboo/concrete interface. Particularly if the bamboo is moulded into a
specific shape (hooks, ties, stirrups etc.) this could lead to the treatment having irregular
distribution along the bamboo, therefore creating inconsistent layer sizing which could have
adverse effects on reinforcement results.
2. Adhesion properties of the chosen treatment substance being applied to the bamboo. Must
be adhesive enough as so the bamboo cannot ‘slide’ out of the concrete.
3. Water repellent properties and effectiveness of selected substance.
4. Must cooperate with the alkali-silica reaction which already happens in concrete. This
reaction happens with the cement which is highly alkaline, and aggregate which is reactive
non-crystalline silica (FHWA, 2012).
3.4.1.2.
Adhesion Strength
On top of water absorption being an issue, bamboo’s outer layer has a smooth waxy coat, which will
prevent adhesion. Steel rebar increases adhesion with ‘ribs’ which are added during the
manufacturing process. A similar approach can be taken with bamboo, by first sanding away the
smooth outer coat, and then creating a surface modification. This topography change can be
achieved either by cutting small portions out of the edges of the bamboo, or by helically wrapping
the bamboo in thin wiring.
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4. Design principles
4.1.
Theoretical Viability
Due to known theoretical values as recorded by E. Brink, F. and J. Rush, P. for the U.S Navy, it is
possible to perform calculations, to determine the viability of bamboo reinforced concrete for
essential structural components of a home. These can be done with use of Australian Standards,
AS3600 and AS1170 together with Reinforced and Prestressed Concrete (Y. loo & S. Chowdhury,
2013). Considering beams have the highest amount of tensile strain under normal loading conditions
in comparison to other structural components (beams, columns, slabs and floors), theoretical
calculations have been made on beams with applied residential loading conditions. The residential
loading conditions are in accordance with Australian Standards. These calculations are to determine
whether or not bamboo’s tensile strength will be suitable to provide reinforcement for structural
components in housing.
Calculations can be found in appendix I, and clearly show that bamboo can in fact support these
loading conditions, which therefore theoretically supports bamboo as a reinforcement material.
However these calculations do not take cracking of the concrete into account. If cracking is present,
the concretes durability and strength will be negatively affected. The foremost hurdle of bamboo
reinforced concrete, and the lack of its use, occurs due to bamboos water absorption. This can cause
cracking and a lack of adhesive bonding between the bamboo and the concrete, hence why a
specific impervious treatment is necessary.
4.2.
Treatment Considerations
As has been determined in the literature review, a water resistant treatment will need to be applied
to the bamboo before applying it as reinforcement to concrete. In all cases of treatment
applications, only a thin coating shall be applied. A weaker bond with the concrete may be created
with a thicker coat, due to lubrication of the bamboo. Varying treatments shall be analysed in a pullout bonding test.
4.2.1. Bituminous Paint
Due to its water repellent nature, adhesive qualities, and ability to be locally sourced in Indonesia as
a coal by-product, bituminous paint appears to be the perfect option as a water proofing treatment
for bamboo reinforced concrete. To be applied as a fine layer, either as a brush coat or dip coat.
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4.2.2. Paraffin wax with helical copper wire
Paraffin wax is also a by-product of Indonesian industry, and it has high impervious qualities.
However due to its low level of adhesion, an extra treatment will be necessary as to resist sliding of
the reinforcement within the concrete. This will be in the form of 1.5mm diameter copper wire
helically wrapped around the wax coated bamboo.
4.2.3. Epoxy with fine sand
Epoxy is widely known for its water repellent attributes. Considering epoxy sets with quite a smooth
finish, a low adhesion bond between the bamboo and concrete will be had and it may be possible for
the bamboo to slide out of place. Therefore fine sand will be added immediately after applying the
epoxy coat to increase adhesiveness against the concrete. Only a very fine film of epoxy will be
needed.
4.2.4. Topography manipulation
A trial of the manipulation of bamboo’s surface will be run. This will be untreated bamboo with its
waxy outer skin removed, along with small evenly distributed triangular cuts into the edges of
bamboo made with a v-edged knife. No coating shall be applied and any adhesion differences shall
be monitored on the post-expanded concrete.
4.2.5. Controlled
Finally, a control will be added to the trials. This will simply be untreated bamboo with its outer skin
removed.
4.3.
Concrete mix ratio
Techniques used for concrete construction will not be changed. The concrete mix used however
should be done so with as low percentage of water as possible, resulting in a low slump, however it
still must allow workability. This will be to ensure the moisture absorption into the bamboo is at an
absolute minimum.
4.4.
House design and load bearing
The house design shall be assumed as cement block masonry and shall be a simple rectangular
residential dwelling with symmetrical room positioning which will include 3 bedrooms, 1 bathroom,
1 kitchen and 1 living-room. Load bearing shall reflect the residential loads of AS1170 for structural
design. Further detail can be found in the design calculations in appendix I.
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5. Cost analysis
5.1.
Availability of bamboo vs. steel
As discussed earlier, bamboo is a native plant species to Indonesia and thrives in its natural
environment. It is readily available around Indonesia through many plantations and also grows
independently in the wild. As of 2005 there were 53 different bamboo plantations around Indonesia,
and therefore should be recognised as a highly accessible material within the county (Sulastiningsih,
2012).
Steel on the other hand, is much harder to acquire. There are currently only two major steel
companies of Indonesia, ‘Gunawan Steel Group’ and ‘Krakatau Steel’. These two companies hold a
monopoly of the steel industry in Indonesia, meaning prices are not very competitive (IndoMetal,
2014). In 2011, imported steel rose above 50% of the country’s total consumption, and have
continued to rise and are predicted to keep rising as the countries development is increasing
(IndoMetal, 2014). This shows that the pricing of steel will be unstable and reliant on international
markets as opposed to locally sourced materials. This could see the price and the availability of steel
become inconsistent in Indonesia.
5.2.
Labour intensity
Bamboo reinforcement clearly has a higher level of labour intensity in comparison with steel
reinforcement, as there are more phases it must be put through prior to use. However Indonesian
labour is cheap and considering the skill required for bamboo preparation is relatively low, this price
will be towards the lower end of the labouring cost spectrum. The cost of manual labour in
Indonesia is roughly $150-$180 AUD per month with 10-12 hour days expected, 5-6 days per week
(Oxford Business Group, 2013). As a conservative guide, the maximum wage with the minimum
hours and days worked per week will be used as an hourly wage;
5.3.
Raw materials
5.3.1. Steel Rebar
Domestic rebar prices in Indonesia have been constantly increasing due to scrap supply issues, with
prices averaging at 9,300,000 rupiah per metric ton (Steel Reference Prices (Domestic Markets),
2014) which is currently ≈ 860 AUD, (0.86 AUD per kg) as of September 2014. Assuming 300MPa,
10mm diameter rebar is used; the mass per unit length is 0.617kg/m according to AS4100.
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5.3.2. Bamboo Poles
Pricing of bamboo is dependent on the producer, and which island it is to be sourced from. The
larger Sunda and Maluku islands have a more competitive pricing, with lesser islands being more
expensive due to having less rivalry of producers. Prices for bamboo are commonly charged per 5m
culm as opposed to kg. Indonesian Bambusa Blumeana is relatively light in comparison to other
species, weighing 7.5kg per 5m culm. Typical pricing in Indonesia ranges between 1,800 Rupiah to
10,000 Rupiah per 5m culm (Ladybamboo.org, 2011), translating to 0.02 – 0.12 AUD per kg. For the
purpose of being conservative with the cost analysis, a price of 0.10 AUD per kg will be used.
Bamboo weight per meter:
5.3.3. Treatment materials
Prices of the treatment materials within Indonesia is hard to find, however all materials can be
located on the global trade website www.Alibaba.com and will be used as a reference price. All
prices shown are valid as of September 2014 and are assumed to be bulk ordered therefore inclusive
of freight.
Table 2 - Price list of treatment materials, according to alibaba
Bituminous paint
Paraffin Wax
Epoxy
Fine sand
1.5mm Copper Wire
v-edged knife
5.4.
Can be found from 0.70-1 USD per kg converting to 0.78-1.12 AUD per kg, or
8,424-12,035 Rupiah per kg. Use 0.85 USD/kg, 0.95 AUD per kg.
1 USD per kg (1.12 AUD or 12,035 Rupiah)
2.50 USD per kg (2.80 AUD or 30,087 Rupiah)
0.05 USD per kg (0.056 AUD or 601 Rupiah)
0.06 USD per meter (0.067 AUD or 722 Rupiah)
2 USD each (2.24 AUD or 24,070 Rupiah)
Final cost presumptions
Cost estimation per 100m of final product is to be compared between treatments, with a theoretical
cost viability discussion to conclude the cost analysis. Price comparison will vary over time as the
global market constantly changes, but currency conversion was performed on 19th September 2014
via http://www.xe.com/currencyconverter/ which is when the cost analysis is accurate to, (1 USD =
1.12 AUD = 12,035 Rupiah). Full calculations can be found in appendix I.
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5.4.1. Total cost per 100m comparison
Table 3 – Total treatment cost in AUD per 100m of material
Treatment
Bituminous Paint
Paraffin wax with helical copper wire
Epoxy with Fine Sand
Topography manipulation
Controlled
Steel
Total Cost per 100m (AUD)
$18.11
$46.05
$26.96
$9.59
$5.55
$53.06
5.4.2. Cost analysis conclusions
As can be seen in the above cost analysis, every form of bamboo treatment is at a lower cost than
steel. However, a reasonably lower cost simply isn’t enough to prove viability of the treatment,
there must be a dramatic reduction to compensate for the strength and durability reduction. Both
Bituminous Paint and Epoxy with Fine Sand see drastic reductions in this cost analysis, with
bituminous paint treated bamboo being almost one third the price of steel, and epoxy with fine sand
almost halving the cost per 100m. In conclusion, Paraffin wax does not seem suitable as a
replacement due to its high cost and perhaps unsound technology. Both Bituminous Paint and Epoxy
coatings appear promising and have a large enough price reduction to be feasible. Finally, the
topography manipulated bamboo may cause too much expansion to prove viable, however this will
be further determined after a moisture test specific to Indonesia’s Bambusa Blumeana is conducted.
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6. Laboratory Testing
Research and testing was performed to fully determine bamboo’s viability as a concrete
reinforcement material. Tensile, Moisture content, Water saturation, and pull out testings were
performed with the results presented below.
All testing was performed in Colombia at the Government Municipally of Sabaneta’s testing
laboratory, special thanks to Xiomara Martinez and Carlos Betancur for supervising and helping me
throughout the experiments. Unfortunately the camera used to photograph the experiments was
stolen or misplaced and diagrams have replaced the photos as visual aids.
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6.1.
Tensile test
Tensile test was performed on Indonesia’s Bambusa Blumeana, to determine the ultimate tensile
strength, and therefore ultimately its viability as a reinforcement material.
Three samples from each culm diameter of bamboo were used to create the tensile specimens. As
bamboo is a natural fibre, predictions were that some of the specimens could have performed very
different to others therefore multiple specimens would achieve a higher accuracy in test results.
Nodes were avoided in the 150mm bamboo specimens as to avoid incongruities in results and to
provide a ‘raw’ ultimate tensile strength. A 4-way splitter was used to separate culms into
appropriate splint sizing.
As the manufacture of the specimens was performed by hand, a circular fillet radius from the grip
section to the reduced section was difficult to achieve, and therefore a linear fillet was used as can
be seen in figure 5 below. The reduced section was made to have a width 50% that of the grip
section for all specimens.
Figure 5 – tensile test specimen
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Initially, gripping of the bamboo was a concerning factor, with the smaller diameter culms being
crushed by the clamps (although they were curved) during testing which lead to the ends failing
before the test area. Fortunately larger diameter culmed bamboo were on-hand and available, and
the tensile test was performed with success with the wider bamboo culms, the same notion was
used for the pull out testing.
Full test results can be found in Appendix I, results are outlined below.
Table 4 - Bamboo tensile test results
Culm Diameter
(mm)
40
40
40
60
60
60
80
80
80
Sample
A1
A2
A3
B1
B2
B3
C1
C2
C3
Ultimate Tensile Stress
(MPa)
143.97
119.60
131.57
145.20
159.28
135.65
135.86
172.70
148.02
Graph 1 - Average Tensile Stress vs. Culm Diameter
Ultimate Tensile Stress (MPa)
Average Tensile Stress vs. Culm
Diameter
160
140
120
100
80
40mm Diameter
60
60mm Diameter
40
80mm Diameter
20
0
0
20
40
60
80
100
Culm Diameter (mm)
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Observations
As can be seen in graph 1 above, the average ultimate tensile stress shows a mild increasing trend,
perhaps logarithmic. This trend was expected and is explained earlier within the Literature Review at
Section 3.2.4; plant maturity, culm diameter, and density are all positively correlated with the plants
aging process. Therefore it can be assumed that the plants with the larger culms were older and
more mature, thus had denser fibres and a higher ultimate tensile strength (However once a plant is
fully mature, strength and culm diameters no longer increase).
The ultimate tensile strengths for the three diameters of bamboo trialled were all greater than the
theoretical value of 124.1Mpa as stated in Section 3.2.3, with the all-round average ultimate tensile
strength being 143.54kN. The theoretical viability calculations performed in Section 4.2 used the
theoretical tensile strength value and proved that bamboo was in fact a viable reinforcement
material for structural concrete (residential homes). Therefore a conclusion can be drawn from the
tensile testing and theoretical calculations, that Indonesia’s Bambusa Blumeana is a viable species
for bamboo reinforced concrete, in terms of tensile strength.
An interesting observation of the failure method of the splints was made during the tensile testing.
The inner fibres seemed to fracture in shear along the grain, while the outer fibres elastically
deformed/elongated.
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6.2.
Moisture content testing
A simple oven drying test was performed on the bamboo to determine its initial water content. The
bamboo used had already been open-air dried for a minimum of 3 months i.e. already treated for
structural use. This test is to determine the moisture content of the prepared bamboo, to discover
and confirm relationships between moisture content and performance.
Table 5 – Moisture content of Bambusa Blumeana
Sample
A
B
C
Moisture content (%)
7.84
8.93
9.62
Average
8.80
Observations
As can be seen in table 5, the average moisture content of the three samples is 8.80%, which is
substantially lower than the desired 15% for ideal bamboo strength and durability. A trend was
observed that as the bamboo sample got larger, so did the moisture content. This is explained
earlier, as the plant grows into full maturity, its water content increases. As also outlined in section
3.2.2.1, the mechanical properties of bamboo are drastically lower when the bamboo is saturated.
This test shows that Bambusa Blumeana has naturally lower water content for a bamboo, which
therefore provides more eligibility for use of the species in a structural situation.
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6.3.
Water Saturation Testing
Furthermore a water saturation test was performed on the treated bamboo to evaluate their
impervious properties. Bamboo splints with coatings were initially weighed then submerged in water
for 72 hours. They were then removed from the water chamber and patted dry with paper towels
and then re-weighed to assess any water permeability. Permeability was assessed by the increase in
water mass compared to the initial mass of the samples.
Table 6 – Permeability of applied coatings
Sample
Bituminous paint
Paraffin wax with helical copper wire
Epoxy with fine sand
Control
Permeability (%)
0.00
0.00
0.00
15.71
Observations
As can be seen all coatings had a 0.00% permeability rating with no dimensional changes, therefore
all coatings are fully passable to be used as reinforcement in terms of possible dimensional variation
due to water absorption. The control or un-coated bamboo had a 15.71% increase in weight from
the water, and the perimeter of the splint went from 97mm to 102mm, which is a 4.9 % increase.
The uncoated bamboo’s increase in dimensions was actually lower than expected, as stated in
section 3.2.2.2, variation can be up to 20%.
It should be noted that laboratory temperatures were never much greater than 17o Celsius,
therefore the paraffin wax treatment was constantly in solid state. However it is known that
although melting of paraffin wax does not begin until 56o Celsius, the solid branching alkane chains
of paraffin wax begin to deform with temperatures rising above 33o Celsius and consideration of
Indonesia’s tropical climate should be made (Stainsfile.info, 2007).
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6.4.
Pull out test
Pull-out tests from concrete cylinders were performed on all bamboo considerations included within
the design principles, along with a steel sample as comparison. These pull-out tests determine the
bonding shear stress of each sample, which therefore determines the feasibility of the waterresistant treatment methods. A difficulty rating out of 5 was given to each treatment method for
future comparison and analysis, where 1 being the easiest and 5 being the most difficult (1 is
automatically awarded to the unchanged control bamboo). Figure 6 shows these pull out test
apparatus.
Figure 6: Pull out test apparatus
Image source: NSR-10
Methodology
Bamboo rods covered in varied coatings needed to be prepared prior to pull out testing. Bamboo
poles were first cut to length, 300mm each. A 4-way splitter was used to separate culms into
appropriate splint sizing. The rods were shaped to have one singular node located approximately ¼
(75mm) down the rebar, as the spacing between nodes on Bambusa Blumeana appeared
approximately 250-350mm, and therefore for more real-world-applicable results were obtained.
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Bituminous Paint
Applying the bituminous paint was quite simple. Local warehouse stores supplied a
bituminous paint, ‘Bitubond’ which is quite a heavy and thick paint. The paint was prepared
and put into a paint pressure sprayer, then simply sprayed onto both sides of the bamboo,
with careful inspection as to confirm the whole splint, including edges, was completely
covered. Paint left to dry for 72 hours in the laboratory, only one coating was needed.
Difficulty rating: 2.
Paraffin wax with helical copper wire
Applying this coating proved to be a difficult task in itself. Firstly the paraffin wax was melted
in a large cooking pot over several hours. The copper wire was then helically wrapped
around the bamboo splint, and then dipped into the liquid wax. After solidification and first
inspection, it was noted that there were many inconsistencies with the surface and the now
treated bamboo rebar was far larger than desired (over 200mm perimeter). The reverse
process was applied, with the splint dipped into the liquid wax then wrapped in the wire.
There were far less surface inconsistencies and the bamboo rod was significantly smaller
than the former application. Difficulty rating: 4.
Epoxy with fine sand
This coating had a similar procedure to the bituminous paint. The epoxy was simply placed
into an open container, with the fine sand slowly and carefully mixed in. The original mix of 5
parts epoxy, 1 part fine sand was used and the blend appeared rough enough to suit
adhesion desires. The blend was then loaded into a pressure sprayer and simply sprayed
onto both sides of the bamboo, with careful inspection as to confirm the whole splint,
including edges, was completely covered. The bamboo rebar was left to dry for 72 hours in
the laboratory, only one coating was needed. Difficulty rating: 3.
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Topography manipulation
The process for shaping the topography proved to be a little complicated, as the sizes being
worked with were quite small. It was decided that ½ of the width of the splint was to remain
constant and untampered, with ¼ of width, along each edge allowing for manipulation. A
blunt “rack teeth” shape was carefully carved into the bamboo, with teeth running for
10mm, pitch of the indent ran for 5mm on each side, and the indent itself ran for 5mm. The
final shape can be seen in figure 7 below. Difficulty rating: 5.
Figure 7 – topography manipulation of bamboo rod
16 concrete cylinders were then made using 200x100mm moulds, each with a different coated
bamboo rod immersed 150mm deep through the centre, along with control bamboo and steel
reinforcement for comparison. 3 different diameter sizes were used per bamboo rebar, to analyse
the best diameter for tensile strength to shear bond ratio.
The concrete within the cylinders was constant and a low-moisture 25MPa ARGO mix was used
throughout. Concrete was water cured by immersion, testing was performed at 28 days. Standard
pull out test apparatus was used (NL 4016 X/002 hydraulic pump); application of force was slow and
periodised at 0.5kN per second. Results displayed table 7 and graph 2.
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Table 7 – Pull out test results
Bond Shear Stress
Sample
(MPa)
Failure Method
Bituminous A
2.772
Bamboo failed in tension
Bituminous B
3.695
Bamboo failed in tension
Bituminous C
4.844
Bamboo failed in tension
Paraffin A
0.156
Bamboo rebar slipped and was pulled out
Paraffin B
0.344
Bamboo rebar slipped and was pulled out
Paraffin C
0.228
Bamboo rebar slipped and was pulled out
Epoxy A
1.983
Bamboo failed in tension
Epoxy B
1.022
Bamboo rebar slipped and was pulled out
Epoxy C
4.670
Bamboo failed in tension
Topography A
1.025
Bamboo ribs sheared and rod pulled out
Topography B
0.938
Bamboo ribs sheared and rod pulled out
Topography C
1.345
Bamboo ribs sheared and rod pulled out
Control A
1.555
Bamboo rebar slipped and was pulled out
Control B
1.715
Bamboo rebar slipped and was pulled out
Control C
2.365
Bamboo rebar slipped and was pulled out
Ribbed Steel
8.934
Steel rebar was pulled out with concrete deformation
Reinforcement
Where ‘A’ represents 40mm diameter, ‘B’ represents 60mm, and ‘C’ represents 80mm.
Bonding Shear Stress (MPa)
Graph 2 – Pull out test comparisons
10.000
9.000
8.000
7.000
6.000
5.000
4.000
3.000
2.000
1.000
0.000
Bamboo Reinforced Concrete
20mm Diameter
30mm Diameter
40mm Diameter
Ribbed Steel
Reinforcement
Page 32 of 51
Figure 8 – Example diagram of finished cylinders with embedded bamboo
Observations
Many test results showed that the bamboo failed in tension before slipping and therefore the bond
stress is not ensured, however it was observed that as the bamboo rods failed in tension and did not
simply slide out of place there was indeed some bond created. Therefore the tensile failure value is
used as the maximum bond strength.
Both the bituminous paint and epoxy treated bamboo performed very well in the pull-out test and
proved that acceptable bond strength can be produced with a simple water-proof coating. The
bituminous recorded 4.844MPa at its highest, and the epoxy’s greatest shear was at 4.670MPa, both
these values are slightly above half that of steel’s recorded bond strength. There is no specific set
Australian standard to minimum bond strength between reinforcement and its surrounding
concrete; however AS3600 states a recommendation to a well-bonded interface between the two as
having a minimum of 3.0MPa shear failure. Therefore it can be seen that the bituminous treatment
at 60 and 80mm diameters, along with the epoxy and fine sand blend at 80mm diameter, all qualify
this recommended condition. It should be noted that honey combing occurred in the Epoxy A trial,
this did not appear to affect pull out results at all.
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The paraffin wax treatment yielded poor experimental results. Very low adhesion was achieved
between the concrete and the wax. As the rod was pulled out, the copper wire remained within the
cylinder for all three trials. The design did not perform in a way to suggest the wax as a suitable
coating for the bamboo in a reinforcement situation.
Mild external cracking was present on the concrete cylinders for both 60 and 80mm diameter
specimens of the untreated bamboo rods, both the control and topography manipulation. It is
known that cracking of concrete during the curing process can be caused by multiple factors; excess
water in the mix, rapid drying of the concrete, etc. However it is also known that as bamboo is a
natural fibre it is subject to water absorption resulting in dimension variation, as outlined in Section
3.4.1.1. Considering the other cylinders didn’t experience any visible cracking, it can be assumed the
cracking was due to the dimensional variation in the uncoated bamboo. There could also have been
a rapid drying effect created as the ends of the bamboo rebar were in open-air, creating some
evaporation via water absorption passing through the bamboo and then into the atmosphere,
however the experiment was performed in a cool, dry, and closed laboratory, evaporation speed
would have been minimal. Therefore an educated assumption can be made that the cracking of the
cylinders was in fact due to dimensional variation of the bamboo via water absorption. Aside from
the external cracking of the concrete, the uncoated control bamboo performed quite well, all round
having higher bond strength than the topography manipulated bamboo rods and the paraffin wax
coated rods. This suggests that the topography manipulated rods were simply a waste of time.
Although the control’s greatest bond strength was only 2.365MPa, which does not quite reach the
AS3600’s recommended 3.0MPa, it was still observed to perform better than expected, and still
showed that rebar constructed from untreated Bambusa Blumeana alone was able to create at least
some bond with the concrete, and the expansion/contraction during the curing process only created
minor cracks to the surrounding concrete, without creating a gap for the bamboo to freely move.
The rods were moved around as to monitor any looseness within the cylinder, none was recorded.
As can be seed in graph 2, a general trend of increasing bond strength appears from smaller to larger
diameter. This was expected as bond failure stress is directly proportional to submerged surface
area. In some circumstances however, outlying occurrences were seen. These breaks from the trend,
such as the 60mm diameter results in both the epoxy and topography manipulation, can be
explained by possible experimental errors such as; mistakes during manufacture, non-symmetrical
test pieces causing eccentric loading, grip discrepancies and damage to the bamboo via gripping too
severely.
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Note: Free end slip measurements were not taken, as measuring apparatus such as a linear variable
differential transformer was unavailable. Observations were taken post-experiment to determine
any slip but it was impossible to distinguish due to the miniscule measurements that could be
expected (tenths of millimetres).
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6.5.
Discussion
As was seen throughout section 7, bamboo has a great potential as an alternative reinforcement
material. This section presents a discussion of the tests conducted which investigated the tensile
strength and moisture content of Bambusa Blumeana, permeability of treatment methods, and
bond strength of the designs created.

The tensile strength of Bambusa Blumeana was shown to be higher than that of the given
theoretical value. Multiple test were carried out, as it is difficult to realise the actual strength
in structural members on one specimen due to bamboo being a natural fibre having a high
sensitivity to notches, irregularities in grains, and overall defects in material. Results from
the multiple runs had the bamboo prove its natural tensile strength. However it should be
noted that bamboo previously tested for tensile strength which have included a nodal region
have yielded weaker results than their non-nodal counterparts, although still exhibit the
same failure trends. This detrimental effect caused by the node was reduced as fibre to
volume ratio increased i.e. more mature plants (Correal D and Arbeláez C, 2010). Hence it
may prove beneficial to re-test the bamboo including nodal regions, to get a more accurate
representation of the actual ultimate tensile strength.

Moisture content in the species is low, providing a high level of appropriateness for in terms
of use of Bambusa Blumeana in structural situations, as previously explained.

All applied coatings were determined to have faultless water proofing properties. This was
expected as highly impervious materials were selected. The bamboo’s water absorption
however was unexpectedly low, having a 15.71% increase in weight, and only a 4.9%
increase in dimensions. This low increase in dimensions could lead to acceptability of simple
uncoated Bambusa Blumeana as an alternative reinforcement material, as lower
dimensional variation will lead to less effect on bondage as well as cracking.

The pull-out tests showed that out of all designs, the bituminous paint and epoxy with fine
sand coatings performed the best. The effectiveness of the fine sand is questionable and
perhaps just an epoxy coating should have been used to first determine the bonding
strength of a more simple coating. As bituminous paint had the stronger bond strength with
the lowest effort output per-coating it is therefore concluded the most effective treatment.
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
Although the paraffin wax coating was completely impervious, it also yielded the lowest
bond strength, and failed any reasonable coating expectations.

Topography manipulation made the bamboo rod weaker in shear in comparison to the
control, which is ultimately exertion of effort for a lesser result, therefore also fails
reinforcement treatment expectations. The control bamboo showed promising results in its
bond strength, although they were only very mild surface cracks, cracking was still present in
the uncoated bamboo, showing vulnerability in the curing process.

During the testing there were some recordings taken and suggestions made as to improve
final results and conclusions.
1. Running more trials per coating diameter. As there was a limited time frame,
budget and equipment (cylinder moulds in particular), only one trial per coating
was able to be taken. As is commonly known in the experimental world, the more
trials performed the higher the accuracy, lower the error and outliers may be
eliminated.
2. Re-perform trials with admixes, such as water reducers/retarders, in the concrete.
This would allow for more water use in the concrete to increase workability. For
the uncoated rebar, the flocculation of water molecules could also have a
retarding effect on water transfer to the bamboo (Engr.psu.edu, 2014), therefore
possibly leading to less cracking within the concrete.
3. The pull out testing apparatus along with the tensile test machine were quite
basic, and a more advanced machine which could record not only tensile force
applied, but strain and deformation, end slip measurements, and computer
technology which can analyse this all throughout the experiment should have
been used. This would give a better representation as to the actual behaviour of
the bamboo throughout the tests.
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7. Conclusion and Future Work
The overall purpose to this research thesis was the evaluation of the use of Bambusa Blumeana, an
Indonesian species of bamboo, as a reinforcement material for structural concrete in residential
housing. From previous studies on bamboo and bamboo reinforced concrete, along with laboratory
testing the following conclusions, along with future work recommendations have been established.
7.1.

Conclusions
After extensive research through already available literature on bamboo replacing steel as a
reinforcement material in concrete, clear conclusions that bamboo can in fact be used as
reinforcement in a residential concrete house were made. Factors such as tensile strength,
availability of bamboo, design calculations, and costing have all been considered and this
lead to theoretical viability of bamboo reinforced concrete. However, water absorption is an
unfavourable inherent material limitation which can lead to poor bonding between the
concrete and bamboo, and cracking of the concrete during the curing process. This needs to
be rectified before bamboo can be used as a reinforcement material for concrete.

Laboratory material property tests were performed on Bambusa Blumeana, proving that it
had a high tensile strength as is needed in a reinforcement material. Ultimate tensile stress
reached as high as 172.70MPa. Tests showed that the species had naturally low moisture
content at 8.80%, along with a low water absorption rate and dimensional variation
compared with other bamboos. These material tests concluded that Bambusa Blumeana
appeared to be a suitable species of bamboo to use as a replacement to steel in reinforced
concrete.

Due to the tensile strength of bamboo compared with steel, along with the known fact that
natural fibres hold a tendency to be unpredictable under differing loading conditions, the
reinforcement capabilities of bamboo shall only be considered for small residential houses
with a maximum of 2 stories. Any building with a greater height than this should be strictly
designed to standards with steel reinforcement as to ensure maximum safety.

Laboratory pull-out testing of the bamboo after treatment showed that covering a bamboo
rod with an impervious material does not allow for any water transfer between the rebar
and the concrete mixture during the curing period, therefore eliminating any cracks due to
dimensional increase in the bamboo. The bituminous paint coating, and the epoxy with fine
sand coating both surpassed expectations of bond strength, showed no sign of concrete
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cracking during curing, and had simple application techniques. All of which point to the
liability of these treatments. Un-coated bamboo also had optimistic bond strength, as little
to no bond was expected due to the dimensional change. Further research into modifying
the concrete blend with admixtures could be performed to determine perhaps an even more
simple approach to bamboo reinforced concrete.

The cost analysis performed on the treatment methods and overall process of bamboo
reinforced concrete also showed liability in the replacement method. Although the analysis
was performed via a global trade website, the materials required will be harder to acquire in
3rd world community situations. Factors such as transport pathways and island distribution
need to be considered. Also, the application process for the coatings turned out to be quite
tedious, it was simple but took longer than expected. In a large scale production, applying
coatings by hand will need a large amount of labour and will reduce the cost effectiveness. It
will however be beneficial to the national economy as it will create local jobs. As the
bituminous paint coating can locally be derived from by-products of the already established
coal industry in Indonesia, it is the obvious choice of coating.

Finally, from the above statements, it can be concluded that coated bamboo rods can be
used as a viable form of reinforcement for concrete. The facts that they are a low costing,
easy to manufacture and renewable material make the reinforcement option sustainably
sound. However, this is based on the principles outlined in this thesis, mainly bamboo’s
tensile strength and the use of treatments to provide water absorption resistance. Further
research must be conducted to create a standardised statement confirming the liability of
bamboo reinforced concrete.
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7.2.
Future Work
Conclusions of this thesis state that that bamboo shows potential as a renewable reinforcement
material, however there is still work to be performed on the subject. The following
recommendations have been designed for future work efforts to further research the viability of
bamboo reinforced concrete.

Now that it has been determined that the coatings applied eliminate any size fluctuation
throughout the curing process, the next step shall be designing the implementation of
treated bamboo into structural components. Slabs, beams, columns, and perhaps
foundations could now be designed. Consideration of prior research on timber reinforced
components need to be taken, e.g. previous results on bamboo reinforced beams have been
shown to increase their loading capacity almost 30% when doubly reinforced, along with the
elastic modulus being more than double that of a singly reinforced beam (Sevalia, Siddhpura
and Agrawal, 2013).

After the design process, fabrication and testing of these elements can begin. Factors such
as element cracking and ultimate load strengths should be considered, along with shear
strengths and load combinations.

The life cycle of these components should be considered. No long term effects of the
chemical alkali-silica reaction upon the bamboo have been considered. Further long term
testing needs to be performed to determine the design life of bamboo reinforced concrete.

Depending on the desire of technical results, strain gauges can be placed on the bamboo as
to determine the specific elastic modulus of Bambusa Blumeana. More specific observations
throughout testing may be performed such as elongation distribution during tensile tests.
This will help determine whether bamboo undergoes a uniform elongation whilst under
tension and in turn will provide beneficial information for the design process.

Furthermore, if bamboo reinforced concrete was to be implemented on an industrial scale, a
standardization of material qualities shall have to be arranged. E.g. implementing a
straightness tolerance on bamboo culms to ensure even distribution of load bearing.
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8. References
1. Bambooland.com.au, (2014). Planting & growing guide for bamboo: Information. [online]
Available at: http://www.bambooland.com.au/information/planting-growing-guide-forbamboo [Accessed 29 Jul. 2014].
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Appendices
Appendix I – Results and Calculations
Cost analysis calculations
Table 8 – Bituminous Paint Treatment
Materials
Bamboo
Bituminous Paint
Labour for preparation
Amount
required
100m
3.75kg
3hrs
Total
Calculations
Total cost (AUD)
100m x 0.375kg/m = 37.5 kg
37.5kg x $0.10/kg = $3.75
9.375kg x $0.95/kg = $3.56
3hrs x $3.60/hr = $10.80
$3.75
$3.56
$10.80
$18.11
Table 9 – Paraffin wax with helical copper wire treatment
Materials
Bamboo
Paraffin wax
Copper wire
Labour for preparation
Amount
required
100m
3.75kg
300m
5hrs
Total
Calculations
Total cost (AUD)
100m x 0.375kg/m = 37.5 kg
37.5kg x $0.10/kg = $3.75
3.75kg x $1.12/kg = $4.20
300m x $0.067/m = $20.10
5hrs x $3.60/hr = $18.00
$3.75
Calculations
Total cost (AUD)
100m x 0.375kg/m = 37.5 kg
37.5kg x $0.10/kg = $3.75
3.75kg x $2.80/kg = $10.50
1.875kg x $0.056/kg = $0.11
3.5hrs x $3.60/hr = $12.60
$3.75
$4.20
$20.10
$18.00
$46.05
Table 10 – Epoxy with fine sand treatment
Materials
Bamboo
Epoxy
Fine Sand
Labour for preparation
Amount
required
100m
3.75kg
1.875kg
3.5hrs
Total
$10.50
$0.11
$12.60
$26.96
Table 11 – Topography manipulation treatment
Materials
Bamboo
V-edged knife
Labour for preparation
Amount
required
100m
1 pcs
1 hr
Total
Bamboo Reinforced Concrete
Calculations
Total cost (AUD)
100m x 0.375kg/m = 37.5 kg
37.5kg x $0.10/kg = $3.75
1 x $2.24 = $2.24
1hrs x $3.60/hr = $3.60
$3.75
$2.24
$3.60
$9.59
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Table 12 – Controlled
Materials
Bamboo
Labour for preparation
Amount
required
100m
0.5 hrs
Total
Calculations
Total cost (AUD)
100m x 0.375kg/m = 37.5 kg
37.5kg x $0.10/kg = $3.75
0.5hrs x $3.60/hr = $1.80
$3.75
Calculations
Total cost (AUD)
100m x 0.617kg/m = 61.7kg
61.7kg x $0.86 AUD/kg = $47.51
$53.06
$1.80
$5.55
Table 13 – Steel
Materials
Steel
Amount
required
100m
Total
Bamboo Reinforced Concrete
$53.06
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Theoretical bamboo substitution calculations
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Tensile Test Results
Table 14 – tensile test results
Culm
Splint
Diameter
Thickness
Sample (mm)
(mm)
A1
41
A2
40
A3
40
B1
60
B2
59
B3
62
C1
80
C2
80
C3
82
5
6
6
8
7
8
10
10
12
Grip Section
Width (mm)
15
14
14
21
21
23
28
28
30
Reduced
CrossUltimate
Section Width
Sectional Area Ultimate
Tensile Stress
(mm)
(mm2)
load (kN)
(MPa)
10
188.9
27.2
143.97
9
208.3
24.9
119.60
9
208.3
27.4
131.57
14
424.7
61.7
145.20
13
364.5
58.0
159.28
15
457.4
62.0
135.65
18
714.7
97.1
135.86
18
714.7
123.4
172.70
19
882.2
130.6
148.02
Water Saturation Results
Permeability is assessed by the increase in water mass compared to the initial mass of the samples.
Table 15 – water saturation results
Sample
Bituminous paint
Paraffin wax with
helical copper
wire
Epoxy with fine
sand
Control
Mass before
Mass after
Permeability Perimeter
Perimeter
saturation (g) saturation (g) (%)
before (mm)
after (mm)
0.00
103
103
0.087
0.087
0.00
109
109
0.121
0.079
0.059
Bamboo Reinforced Concrete
0.121
0.079
0.070
0.00
106
106
15.71
97
102
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Pull-out Test Results
Table 16 – pull out test results
Sample
Bituminous A
Bituminous B
Bituminous C
Paraffin A
Paraffin B
Paraffin C
Epoxy A
Epoxy B
Epoxy C
Topography A
Topography B
Topography C
Control A
Control B
Control C
Ribbed Steel
Reinforcement
Culm
Splint
Cross-Sectional Perimeter Ultimate
Bond Shear
Pull-out
Failure Method
Diameter Thickness
Area (mm2)
(mm)
load (kN)
Stress (MPa)
Failure Stress
(mm)
(mm)
(MPa)
40
6
320.4
72
30.1
2.772
93.97 Bamboo failed in tension
60
8
653.5
105
58.0
3.695
88.80 Bamboo failed in tension
80
11
1192.2
137
99.8
4.844
83.72 Bamboo failed in tension
40
5
274.9
85
2.0
0.156
7.22 Bamboo rebar slipped and was pulled out
60
8
653.5
118
6.1
0.344
9.28 Bamboo rebar slipped and was pulled out
80
10
1099.6
150
5.1
0.228
4.66 Bamboo rebar slipped and was pulled out
40
6
320.4
69
20.6
1.983
64.44 Bamboo failed in tension
60
8
653.5
102
15.6
1.022
23.86 Bamboo reo slipped and was pulled out
80
12
1281.8
135
94.4
4.670
73.67 Bamboo failed in tension
40
6
320.4
65
10.1
1.025
31.37 Bamboo ribs sheared and rod pulled out
60
8
653.5
98
13.7
0.938
21.04 Bamboo ribs sheared and rod pulled out
80
10
1099.6
130
26.2
1.345
23.84 Bamboo ribs sheared and rod pulled out
40
5
274.9
66
15.4
1.555
56.00 Bamboo rebar slipped and was pulled out
60
7
582.8
98
25.3
1.715
43.37 Bamboo rebar slipped and was pulled out
80
11
1192.2
131
46.6
2.365
39.09 Bamboo rebar slipped and was pulled out
10
78.5
31
42.1
8.934
536.03 Steel rebar was pulled out
The length of bonded interface for all specimens was 150mm.
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The bonding shear stress was calculated as follows:
Where; τb = Bonding shear stress,
F = Applied pulling force (kN),
A = Surface area of material (total area parallel to applied force vector),
A = L x S, L = Length of bonded interface, S = Perimeter of the bamboo cross-section
The assumption of a uniform bond stress is made throughout the pull-out experiment.
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Appendix II
Acronyms:
HVAC – Heating, ventilation and Air Conditioning
BRC – Bamboo Reinforced concrete
AS1170 – Australian Standards Structural Design Actions
AS3600 – Australian Standards Concrete Structures
AS4100 – Australian Standards Steel Structures
AS4671 – Australian Standards Steel Reinforcing Materials
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