Bamboo Reinforced Concrete – Properties, Mix Proportion, Design and Construction

Bamboo reinforced concrete construction follows same design, mix proportions and construction techniques as used for steel reinforced. Just steel reinforcement is replaced with bamboo reinforcement. Properties of bamboo reinforcement, mix proportion of concrete, design and construction technique with bamboo reinforced concrete is discussed in this article.

Nature’s material, bamboo has been widely used for many purposes. Mainly as a strength bearing material. It is used for building shelters from an earlier time.

Bamboo has used for scaffolding works, formwork supporting stands and many in building construction works. These are limited to medium-large projects.

Even though existence of bamboo has been found from centuries, bamboo as reinforcement material is an innovation in the civil engineering construction field. This innovation was based on Clemson’s study that has been conducted in the Clemson Agricultural College.

Bamboo is a biodegradable and renewable in nature. It is energy efficient as it is of natural origin and environmentally sustainable in nature. These properties have forced to use this in the construction field for centuries.

The details on how bamboo is efficient in replacement for steel reinforcement in concrete are discussed in the following sections.

Significance of Bamboo Reinforced Concrete

The steel as a reinforcing material is a demand that is increasing day by day in most of the developing countries. There is situations when the production is not found enough to face the demand for steel.

Hence it is essential to have an alternative that is worth compared to steel. Bamboo is found in abundant, they are resilient and hence these can face the demand as a reinforcing material and become an ideal replacement for steel.

The tensile strength property which is the main requirement of a reinforcing material is seen appreciable for bamboo, compared with other materials including steel. The structure of bamboo from its origin gives this property.

The hollow tubular structure has high resistance against wind forces when it is in natural habitat. Working on the weak points of bamboo and bringing up an innovation of bamboo as a structural steel replacement, would be a great alternative.

Bamboo as Reinforcement for Concrete Construction

The material used as a reinforcement in concrete should show all the essential properties to make the element structurally active under load. In the case of steel, we manufacture steel to the desired proportion and test for the basic strength values as a quality check.

Similarly, the process must be done for bamboo too. Bamboo is found in nature, they have in different species. Each species differs in their characteristics, texture, thickness and strength. Hence it is essential to know which species is best for reinforcing and which is not.

Selection of Bamboo for Reinforced Concrete Construction

Selection of bamboo for reinforcement can be done based on these factors

• Color and Age – Employ bamboo having an evident brown color. This shows the age of bamboo to be at least 3 years.
• Diameter – Use the one with long large culms
• Harvesting – Try to avoid those bamboos that are cut either during spring or summer seasons.
• Species – Among 1500 species of bamboo, the best one must checked, tested to satisfy the requirement as a reinforcing material.

Material Properties of Bamboo for Reinforced Concrete

Bamboo is by its origin an orthotropic material. It posses fibers within it. It gains high strength along the fibers and low strength in the transverse direction.

The bamboo has a structure of a composite material with cellulose fibers aligned across the length. It has high thick fibers near to the outer length of the bamboo, which is the main reason why they resist huge wind forces.

Fig.1: Schematic Diagram of a Bamboo with centroid axis ‘Z’ and height ‘L’

Figure-1 shows a schematic diagram of a bamboo sample. The node that is seen in the bamboo are represented by n. It is subjected to a lateral load ‘p’ causing a maximum moment at the support. It forms a cantilever arrangement.

Water Absorption Property of Bamboo

The main requirement of bamboo when used in reinforcement is the concern for water absorption. The water absorption capacity was studied in various species. Among which Dendrocalamus giganteus, known simply as DG and Bambusa vulgaris hard, BVS are the ones which absorbed less water. The rate of water absorption can also be reduced by certain treatment.

Fig. Water Absorption Rate of different bamboo species with time

To increase its effectiveness in impermeability certain treatment has been carried out. The treatment substance in incorporated in the bamboo material should consider three primary factors:

1. The materials adhesion property towards bamboo and concrete
2. The formation of rough surface on the bamboo for perfect bonding
3. The water repelling property of the treatment substance

Bamboo Strength towards Bonding

As in the case of steel rebar with ribs in it, which facilitate proper bonding with the concrete, bamboo too should have proper adhesion with the concrete.

The bonding strength is based on this adhesive property of cement and the compressive forces that are formed on the surface of the reinforcing bars. An untreated bamboo affects the bonding strength in the following manner:

a) By pushing the concrete away, by the swelling of bamboo material

b) By the formation of voids within the concrete

c) By formation of cracks as the products of void formation

Fig. The Action of an untreated Bamboo as a Reinforcing Material

These problems are well faced by a proper bamboo treatment.

Durability of Bamboo Material

Its property of being a natural product make it more exposed to environmental agents and insects. A remedy against this is to undergo bamboo curing.

The curing process enables the treatment of humidity content and the starch within it, which is the main reason for insect attraction. The curing is effective only if the chosen bamboo is right one. As mentioned in the selection of bamboo.

The curing of bamboo can be done either by:

1. Curing on spot
2. Immersion process
3. By heating
4. Smoke Curing

The treatment must be done when the bamboo is in a dry state so that the penetration undergoes in the right way. The preservation treatment done on bamboo to take care of durability factor should have no effect on the chemical composition. The treatment itself should last, without being washed away under high water conditions if any.

Durability is a major concern for bamboo material. The physical and chemical properties of bamboo are found high with low content of humidity within it. This low content would keep away molds in bamboos.

Fig. A beam Bamboo Reinforcement after 15 years exposed to open air

Fig. A column steel reinforcement bars after 10 years exposed within a closer area

Bamboo reinforcement is found more durable than steel if it has undergone proper treatments.

Bamboo Reinforced Concrete Design Principles

Design of bamboo reinforced concrete is similar to design of steel reinforced concrete. The mechanical properties of bamboo reinforcement to be used for design can be assumed as per table below.

Table: Mechanical Properties of Bamboo Reinforcement

Mechanical Property	Symbol	Value (psi)
Ultimate compressive strength	—	8,000
Allowable compressive stress	s	4,000
Ultimate tensile strength	—	18,000
Allowable tensile stress	s	4,000
Allowable bond stress	u	50
Modulus of elasticity	E	2.5×106

Procedure and equations for the design of steel reinforced concrete can be used for the design of bamboo reinforced concrete by using the mechanical properties of bamboo reinforcement in place of steel reinforcement in the calculation.

Bamboo in flexural members such as beams and slabs develops some cracking under normal service loads due to its low modulus of elasticity. If such cracks in bamboo is not tolerable for structural members, then the structural design can be carried then steel reinforced designs or designs based on unreinforced sections are required.

Bonding between concrete and bamboo as reinforcement is must for design. Split bamboo provides better bonding with concrete than whole culms when used as reinforcement. Bamboo should be split and provided in more compact reinforcement layers for better bonding with concrete.

Concrete Mix Proportions for Bamboo Reinforced Concrete

Water-cement ratio plays an important role in strength and durability of reinforced concrete. Bamboo being a natural building material has the property of absorbing water as discussed earlier. The absorption of water causes swelling of bamboo.

Thus, concrete mix proportion for bamboo reinforced concrete must have water-cement ratio as low as possible. It should also be considered to use concrete with high early-strength cement to minimize cracks caused by swelling of bamboo.

The mix design of concrete can be as per the strength requirement for structure, as per structural design. Since use of reinforcement has no effect on compressive strength requirement of concrete, bamboo reinforced concrete mix proportion can be same as steel reinforced concrete mix design.

Bamboo Reinforced Concrete Construction

The methods used for construction of steel reinforced concrete can be used for bamboo reinforced concrete. It is just the replacement of steel with bamboo reinforcement. All other process for bamboo reinforced concrete construction remain same as conventional concrete construction.

Different Types of Pipe Joints in Plumbing

Types of pipe joints are major components of plumbing system provided to connect multiple pipes. Pipe joint provided should withstand pressure of each pipe.

There are several ways to join pipes, but selection of pipe joint depend upon the pipe size, pipe material and flow pressure etc.

Types of Pipe Joints in Plumbing

Different types of pipe joints used in plumbing system are as follows.

• Threaded joint
• Brazed joint
• Soldered joint
• Welded joint (butt welded, socket welded)
• Flanged joint
• Compression joint
• Grooved joint

Threaded Joint in Pipe

Threaded joint means, pipes are connected by screwing with the help of threads provided for each pipe. One pipe having internal threads and the other one having threads externally. Cast iron pipes, copper pipes, PVC and G.I pipes are available with threads.

Threaded joints are available from 6mm diameter to 300mm diameter pipes. They are preferable for low temperature areas and low pressure flows. In the areas of high temperature, the joints may expands and leaked due to thermal expansion. Installation of threaded joint is easy but good maintenance required.

Brazed Joint in Pipe

Brazing is the process of jointing pipes using molten filler material at above 840oC. Brazing is generally used for joining copper pipes or copper alloy pipes. The filler material majorly consist tin which has great affinity towards copper. But because of its weak property tin is added to other materials like nickel, bismuth, silver and copper.

The melting point of parent metal should be higher than filler metal. Mechanical strength of brazed joint is low compared to other joints. This type of joint is suitable in moderate range of temperature areas.

Soldered Joint in Pipe

Soldering is also similar to brazing but the only difference is in case of soldering the filler metal melts at below 840oC. Soldering also used to joint copper and copper alloy pipes. Before proceeding to soldering flux called paste is applied to pipes and fittings to prevent them from oxidation from flame. Here also we require skilled workers for installation.

Soldered joints are suitable for low temperature areas. These are having low mechanical strength as brazed joints.

Butt Welded Joint in Pipe

When the pipes are of same diameter butt welding is to done to join the pipes. It is the most common type of welding. Skilled workers are required to install the joint. These joints are generally used for large commercials and industrial piping systems.

Butt weld provides good strength for the joint and it can resist high pressure because of smooth and continuous surface inside the joint. Butt weld joints are expensive, to make it economical sometimes internal weld backing rings are used, which joins the pipe with less amount of filler material. But these rings may fail under heavy stress and cracks are developed.

The joints are fixed and do not opened for maintenance purposes. External smoothing of welded portion will give good appearance to the piping system.

Socket Welded Joint in Pipe

Socket welded joints are used wherever there is a high chance of leakage in joints. Pipes are connected as putting one into other as shown below and welded around the joint. Pipes having different diameters are suitable for this type of joint.

If pipes having similar diameter, then required fittings are used. Welding cost is generally lower than butt welding. Fatigue resistance is lower for socket welded joints when compared to butt weld joints. However, socket welded joint give good results when compared with other mechanical joints.

Flanged Joint in Pipe

Flanged joints are used for high pressure flows and for large diameter pipes. In general they are used for plain end pipes or threaded pipes. Two flange components are connected by bolts at the pipe joint to prevent leakage.

Generally these are made of cast iron, steel etc. these are having good strength and do not fail against high pressure. Against high temperatures the bolts may fail under creep lost their grip so, fixing of bolts should be done properly while installing. They are also useful for repairing pipelines and maintenance purposes.

Compression Joint in Pipe

When the pipes have plain ends they are joined by installing some fittings at their ends then that type of joint is called compression joint. The pipe ends will be fitted with a threaded fittings or couplings hence they are connected.

So, in this case we can connect pipes of different materials and different sizes. But the joints should be properly fitted to resist flow pressure otherwise they may fail and leakage occurs. Compression fittings are available in different materials and selection of fittings may depend upon our requirement.

Grooved Joint in Pipe

In case of grooved joint, the pipe ends consist grooved edges which are connected by elastomer seal and then ductile iron made grooved couplings are used as lock for elastomer seal. This grooved couplings are connected by bolts. These joints are easy to install and economical.

Grooved joints will give good resistance against pressure and allows moderate axial movement due to thermal expansion. But, in high temperature Areas elastomer seal may lost its strength and torsional failure occurs. So, these are permitted to moderate temperature areas.

Grooved joints are easily removable so, for maintenance purposes of pipes these joints are preferable.

Rainwater Harvesting

Generally, a lot of rain water would go in drain flowing from the roofs of houses and the street. Rain water harvesting is requiring conserving the water and recharging the underground water which helps when there is a water scarcity.

When there is too much rain we can collect all the water at roof and via piping system it can be transferred to underground water after filtering so that it can be reused for household purposes.

Also we can send the rain water flowing on the streets to underground water after proper filter system so that it could be used in the dry seasons. In few places the underground water level goes down so much extent that wells, tube wells are dry in these places.

There should be a provision of sending rain to go underground to increase underground water level so that it brings water level of wells and tube wells back to normal. There are many ways to send rain water to underground to increases the underground water level.

Most simple way to recharge is to dig a pit in the ground and make a filtering system so that clean rain water can reach underground and can be reused.

Location of the pit should be on a clean ground surface so that polluted water doesn’t go underground through the pit. The pit should be deep enough so that rain water would be reach the porous layer of soil as it allows the water to pass though it and get added to the underground water.

But water flowing thru the street will still be polluted so we need a filter layers in the pit. First we need a clean big stone or boulders layer of specific thickness. Than above that layer we put layer of clean gravel which is almost as thick as the first layer of boulder.

Then finally on the top we put the clean sand make sand layer almost as thick other layers. This completes the filter system and the pit is called recharge pit. A recharge pit is usually 10 to 15 feet deep.

The depth of these pits depend upon the nature of soil underneath and volume of water recharge well is expected to receive during heavy rains. For the rain water flowing on the street we can make clean drain or narrow channels on the street which would help rain water reach the recharge pit from surround the park or other street areas.

Generally house users shouldn’t put garbage on the streets and there should be proper removal of garbage periodically by the concerned dept. The rain water from roof can be stored in a domestic tank and can be used year long for daily usage of the occupants.

Rainwater Filter Process

How the water gets filtered in the recharge pit?

While the rain water from streets overflow passes through the primary sand layer it separates dirty soil from the rain water and makes its clean. Then rain water pass through the secondary layer which ensures that rain which has carried some amount of sand gets filtered out from gravel layer.

Finally, the water passes through the boulder layer. The boulder layer actually gives support to upper layer and allows rain water to pass easily to the porous soil and get added to the underground water treasure. This underground water is clean and would supply drinking water as well as other domestic purposes or for household gardens whole year through tube wells and wells

Ground water recharge is important aspect of rain water harvesting and has to be taken into practice everywhere.