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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


Charles Darwin University


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. Bonding issues ............................................................................................................... 16

4. 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

5. 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. Final cost presumptions ........................................................................................................ 21

5.4.1. Total cost per 100m comparison .................................................................................. 22

5.4.2. Cost analysis conclusions .............................................................................................. 22

6. 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

7. Conclusion and Future Work ........................................................................................................ 38

7.1. Conclusions ........................................................................................................................... 38

7.2. Future Work .......................................................................................................................... 40

8. 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

Bamboo Reinforced Concrete Page 5 of 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.


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.


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.


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.


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 3-

10cm 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).


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.


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

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

3.2.3.1. 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).


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.


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.


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

http://panchesatoko.blogspot.com.au/

http://earthodyssey.net/2007/09/indonesia/


masonry lacking structural reinforcement, or timber stilted homes, with the majority of reinforced-

concrete 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.


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).

http://www.ijser.org/


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.


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 pull-

out 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.


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.


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.


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 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.

Paraffin Wax 1 USD per kg (1.12 AUD or 12,035 Rupiah)

Epoxy 2.50 USD per kg (2.80 AUD or 30,087 Rupiah)

Fine sand 0.05 USD per kg (0.056 AUD or 601 Rupiah)

1.5mm Copper Wire 0.06 USD per meter (0.067 AUD or 722 Rupiah)

v-edged knife 2 USD each (2.24 AUD or 24,070 Rupiah)

5.4. 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.

http://www.alibaba.com/

http://www.xe.com/currencyconverter/


5.4.1. Total cost per 100m comparison

Table 3 – Total treatment cost in AUD per 100m of material

Treatment Total Cost per 100m (AUD)

Bituminous Paint $18.11

Paraffin wax with helical copper wire $46.05

Epoxy with Fine Sand $26.96

Topography manipulation $9.59

Controlled $5.55

Steel $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.


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.


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


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

Sample Culm Diameter

(mm) Ultimate Tensile Stress

(MPa)

A1 40 143.97

A2 40 119.60

A3 40 131.57

B1 60 145.20

B2 60 159.28

B3 60 135.65

C1 80 135.86

C2 80 172.70

C3 80 148.02

Graph 1 - Average Tensile Stress vs. Culm Diameter

0

20

40

60

80

100

120

140

160

0 20 40 60 80 100

Ult

imat

e T

en

sile

Str

ess

(M

Pa)

Culm Diameter (mm)

Average Tensile Stress vs. Culm Diameter

40mm Diameter

60mm Diameter

80mm Diameter


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.


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 Moisture content (%)

A 7.84

B 8.93

C 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.


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 Permeability (%)

Bituminous paint 0.00

Paraffin wax with helical copper wire 0.00

Epoxy with fine sand 0.00

Control 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).


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 water-

resistant 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.


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.


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.


Table 7 – Pull out test results

Sample Bond Shear Stress

(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 Reinforcement

8.934 Steel rebar was pulled out with concrete deformation

Where ‘A’ represents 40mm diameter, ‘B’ represents 60mm, and ‘C’ represents 80mm.

Graph 2 – Pull out test comparisons

0.000

1.000

2.000

3.000

4.000

5.000

6.000

7.000

8.000

9.000

10.000

Bo

nd

ing

She

ar S

tre

ss (

MP

a)

20mm Diameter

30mm Diameter

40mm Diameter

Ribbed SteelReinforcement


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.


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.


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).


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.


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.


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


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.


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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Appendices

Appendix I – Results and Calculations

Cost analysis calculations

Table 8 – Bituminous Paint Treatment

Materials Amount required

Calculations Total cost (AUD)

Bamboo 100m 100m x 0.375kg/m = 37.5 kg 37.5kg x $0.10/kg = $3.75

$3.75

Bituminous Paint 3.75kg 9.375kg x $0.95/kg = $3.56 $3.56

Labour for preparation 3hrs 3hrs x $3.60/hr = $10.80 $10.80

Total $18.11

Table 9 – Paraffin wax with helical copper wire treatment




$3.75

Paraffin wax 3.75kg 3.75kg x $1.12/kg = $4.20 $4.20

Copper wire 300m 300m x $0.067/m = $20.10 $20.10

Labour for preparation 5hrs 5hrs x $3.60/hr = $18.00 $18.00

Total $46.05

Table 10 – Epoxy with fine sand treatment




$3.75

Epoxy 3.75kg 3.75kg x $2.80/kg = $10.50 $10.50

Fine Sand 1.875kg 1.875kg x $0.056/kg = $0.11 $0.11

Labour for preparation 3.5hrs 3.5hrs x $3.60/hr = $12.60 $12.60

Total $26.96

Table 11 – Topography manipulation treatment




$3.75

V-edged knife 1 pcs 1 x $2.24 = $2.24 $2.24

Labour for preparation 1 hr 1hrs x $3.60/hr = $3.60 $3.60

Total $9.59


Table 12 – Controlled




$3.75

Labour for preparation 0.5 hrs 0.5hrs x $3.60/hr = $1.80 $1.80

Total $5.55

Table 13 – Steel



Steel 100m 100m x 0.617kg/m = 61.7kg 61.7kg x $0.86 AUD/kg = $47.51

$53.06

Total $53.06


Theoretical bamboo substitution calculations



Tensile Test Results

Table 14 – tensile test results

Sample

Culm Diameter (mm)

Splint Thickness (mm)

Grip Section Width (mm)

Reduced Section Width (mm)

Cross-Sectional Area (mm2)

Ultimate load (kN)

Ultimate Tensile Stress (MPa)

A1 41 5 15 10 188.9 27.2 143.97

A2 40 6 14 9 208.3 24.9 119.60

A3 40 6 14 9 208.3 27.4 131.57

B1 60 8 21 14 424.7 61.7 145.20

B2 59 7 21 13 364.5 58.0 159.28

B3 62 8 23 15 457.4 62.0 135.65

C1 80 10 28 18 714.7 97.1 135.86

C2 80 10 28 18 714.7 123.4 172.70

C3 82 12 30 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 Mass before saturation (g)

Mass after saturation (g)

Permeability (%)

Perimeter before (mm)

Perimeter after (mm)

Bituminous paint 0.087 0.087 0.00 103 103

Paraffin wax with helical copper wire 0.121 0.121

0.00 109 109

Epoxy with fine sand 0.079 0.079

0.00 106 106

Control 0.059 0.070 15.71 97 102


Pull-out Test Results

Table 16 – pull out test results

Sample Culm Diameter (mm)

Splint Thickness (mm)

Cross-Sectional Area (mm2)

Perimeter (mm)

Ultimate load (kN)

Bond Shear Stress (MPa)

Pull-out Failure Stress (MPa)

Failure Method

Bituminous A 40 6 320.4 72 30.1 2.772 93.97 Bamboo failed in tension

Bituminous B 60 8 653.5 105 58.0 3.695 88.80 Bamboo failed in tension

Bituminous C 80 11 1192.2 137 99.8 4.844 83.72 Bamboo failed in tension

Paraffin A 40 5 274.9 85 2.0 0.156 7.22 Bamboo rebar slipped and was pulled out

Paraffin B 60 8 653.5 118 6.1 0.344 9.28 Bamboo rebar slipped and was pulled out

Paraffin C 80 10 1099.6 150 5.1 0.228 4.66 Bamboo rebar slipped and was pulled out

Epoxy A 40 6 320.4 69 20.6 1.983 64.44 Bamboo failed in tension

Epoxy B 60 8 653.5 102 15.6 1.022 23.86 Bamboo reo slipped and was pulled out

Epoxy C 80 12 1281.8 135 94.4 4.670 73.67 Bamboo failed in tension

Topography A 40 6 320.4 65 10.1 1.025 31.37 Bamboo ribs sheared and rod pulled out

Topography B 60 8 653.5 98 13.7 0.938 21.04 Bamboo ribs sheared and rod pulled out

Topography C 80 10 1099.6 130 26.2 1.345 23.84 Bamboo ribs sheared and rod pulled out

Control A 40 5 274.9 66 15.4 1.555 56.00 Bamboo rebar slipped and was pulled out

Control B 60 7 582.8 98 25.3 1.715 43.37 Bamboo rebar slipped and was pulled out

Control C 80 11 1192.2 131 46.6 2.365 39.09 Bamboo rebar slipped and was pulled out

Ribbed Steel Reinforcement

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.


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.


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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