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.

 The node that is seen in the figure presented at the end,  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.

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:

The materials adhesion property towards bamboo and concrete

The formation of rough surface on the bamboo for perfect bonding

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

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.

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.

 Mechanical Properties of Bamboo Reinforcement

Ultimate compressive strength

8,000psi

Allowable compressive stress

 4,000psi

Ultimate tensile strength

18,000psi

Allowable tensile stress

4,000psi

Allowable bond stress

50psi

Modulus of elasticity

E: 2.5×10^6psi

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.

Bamboo reinforcements in beams

Bamboo Water absorption Vs Time

FOR CIVIL SITE ENGINEERS

Following are few general points to remember for civil site engineers to make the construction work easier while maintaining quality of construction.

Lapping is not allowed for the bars having diameters more than 36 mm.

Chair spacing maximum spacing is 1.00 m (or) 1 No per 1m².

For dowels rod minimum of 12 mm diameter should be used.

Chairs minimum of 12 mm diameter bars to be used.

Longitudinal reinforcement not less than 0.8% and more than 6% of gross C/S.

Minimum bars for square column is 4 No’s and 6 No’s for circular column.

Main bars in the slabs shall not be less than 8 mm (HYSD) or 10 mm (Plain bars) and the distributors not less than 8 mm and not more than 1/8 of slab thickness.

Minimum thickness of slab is 125 mm.

Dimension tolerance for cubes + 2 mm.

Free fall of concrete is allowed maximum to 1.50m.

Lap slices not be used for bar larger than 36 mm.

Water absorption of bricks should not be more than 15 %.

PH value of the water should not be less than 6.

Compressive strength of Bricks is 3.5 N / mm^2.

In steel reinforcement binding wire required is 8 kg per MT.

In soil filling as per IS code, 3 samples should be taken for core cutting test for every 100m².

Density of Materials:

Material

Density

Bricks: 1600 – 1920 kg/m³

Concrete block: 1920 kg/ m³

Reinforced concrete: 2310 – 2700 kg/ m³

Curing time of RCC Members for different types of cement:

Super Sulphate cement: 7 days

Ordinary Portland cement OPC: 10 days

Minerals & Admixture added cement: 14 days

De-Shuttering time of different RCC Members

RCC Member

De-shuttering time

For columns, walls, vertical form works: 16-24 hrs.

Soffit formwork to slabs: 3 days (props to be refixed after removal)

Soffit to beams props: 7 days (props to refixed after removal)

Beams spanning up to 4.5m: 7 days

Beams spanning over 4.5m: 14 days

Arches spanning up to 6m: 14 days

Arches spanning over 6m: 21 days

Cube samples required for different quantity of concrete:

Quantity of Concrete

No. of cubes required

1 – 5 m³        1 No’s

6 0 15 m³      2 No’s

16 – 30 m³     3 No’s

31 – 50 m³    4 No’s

Above 50 m³      4 + 1 No’s of addition of each 50 m³

OBJECTIVES OF STRUCTURAL DESIGN

The objectives of structural design is to design the structure for stability, strength and serviceability. It must also be economical and aesthetic.

The design of a structure must satisfy three basic requirements:

1) Stability to prevent overturning, sliding or buckling of the structure, or parts of it, under the action of loads,

2) Strength to resist safely the stresses induced by the loads in the various structural members; and

3) Serviceability to ensure satisfactory performance under service load conditions – which implies providing adequate stiffness and reinforcements to contain deflections, crack widths and vibrations within acceptable limits, and also providing impermeability and durability (including corrosion resistance), etc.

There are two other considerations that a sensible designer ought to bear in mind, viz.,economy and aesthetics. One can always design a massive structure, which has more than adequate stability, strength and serviceability, but the ensuing cost of the structure may be exorbitant, and the end product, far from aesthetic.

In the words of Felix Candela, the designer of a remarkably wide range of reinforced concrete shell structures, It is indeed a challenge, and a responsibility, for the structural designer to design a structure that is not only appropriate for the architecture, but also strikes the right balance between safety and economy.

STRUCTURAL DESIGN BASIS – GENERAL GUIDELINES

Structural design basis starts with the type of structure to be designed. For any structural design to commence, we require certain data. These data includes information about type of structure, site conditions, loading conditions, type of environmental exposure, earthquake zone and wind zone.

Site Conditions:

Structural design of foundation requires soil geotechnical (soil) investigation data i.e. safe bearing capacity of soil, depth of water level below the ground.

Loads on the structures:

1. Dead Loads:

Dead Loads are loads from the self weight of the structural members such as beams, columns, slabs, wall, finishing, plastering etc. Any stationary elements or equipments which may be permanently positioned on the structure shall also be considered as dead load. Dead loads are also called as self weight and is calculated as volume multiplied by its unit weight. Unit of different materials are provided by the standard codes.

2) Live Loads:

Live loads also called as imposed loads are probable loads that the structure may be subjected to during occupancy. These are loads which are moving or dynamic in nature and may or may not be present on the structure during intended use of the structure. For example, for an industrial structure, loads from people, maintenance tools etc. can be called as live loads, while loads from equipments which are stationary at a location is considered as the dead load.

Live loads are different for different types of structures and varies with type of occupancy. For example, for a residential building, live load on floor is considered as 3 kN/m² while for industrial structures or business centers live loads can be taken as 4 or 5kN/m². These loads vary for different structures based on intended use.

Minimum live loads to be considered for design purpose are obtained from respective standard codes based on country or region. ASCE 7 Provides live minimum live loads for buildings and other structures in USA. While in India, IS875 Part-2 provides guidelines for minimum live loads.

For design of any structure, in live loads should be considered based on future expansion plans and all the probabilities of loads which the structure may experience during its lifetime, should be considered.

3. Wind Loads:

Wind loads are horizontal loads on the building which are exerted on the surface area of the building on windward side. This load is calculated based on the wind zone which provides the maximum wind speed in the given zone. This can be obtained from the wind map of the location. This wind speed is converted into force based on the surface area and orientation of building w.r.t. wind direction. Shape of the building is or structural member is also considered for calculation. Wind loads is considered only on those structural members are exposed to the wind or which resists the wind. The guidelines for calculation of wind force on structure is provided by ASCE 7-95 / UBC -1997 /IS 875 : 1987 (Part 3) / BS CP3 : Chapter V : Part2 : 1972 or whichever applicable codes shall be considered based on the location of the building or structure.

4. Seismic / Earthquake loads:

Design for seismic loads shall be carried out as per ASCE 7/ UBC/ IS 1893 or whichever standard code is applicable. The guidelines provided by these applicable codes shall be followed for calculation of earthquake forces.

Design of Structures:

Structural design of buildings or other structures should be carried out as per the relevent code of practice.

Structural concrete Design shall conform to ACI 318-95 / IS 456 : 2000 / BS 8110 : Part 1 : 1985 or other whichever code is applicable.

Structural steel design and fabrication shall conform to AISC-ASD (9th Edition) / IS 800 :1984 / BS 5950 : Part 1 :1990.

Structural design methods are selected based on the local practices. Working stress method, Limit State Method, Load Resistance Factor Design method. These are the methods used for the design of structural members and are guided by the relevant standard code of practice.

Following factors to be considered for design of buildings or other structures and shall conform to the standard codes:

1. Maximum allowable settlement of foundation / structure.

2. Vertical and lateral deflections of buildings, structures as a whole and other structural members.

3.Sliding and overturning of buildings or structures should be checked and prevented by design.

4. Standard detailing guidelines should be followed in drawing.

5. All engineering and design shall comply with relevant and applicable codes of practices, local bye-laws, and rules as per directorate of industries and factories & as listed in Project Design Basis.

6. Environmental exposure conditions should be considered in design and respective factors must be applied in structural member design.

7. Types of construction materials and structural members and their properties should be used during design.

8. Special care should be taken to provide easy escape of occupants during emergency situations such as fire.

These are only few points, many other factors should also be considered which may be relevant for the design. A checklist for different types of structural design should be maintained and followed to prevent any error during design and detailing for buildings and other structures.

 

What is a project?

A project is a temporary endeavor undertaken to create a unique product, service, or result. The temporary nature of projects indicates that a project has a definite beginning and end. The end is reached when the project’s objectives have been achieved or when the project is terminated because its objectives will not or cannot be met, or when the need for the project no longer exists. A project may also be terminated if the client (customer, sponsor, or champion) wishes to terminate the project

People have been undertaking projects since the earliest days of organized human activity. The hunting parties of our prehistoric ancestors were projects for example; they were temporary undertakings directed at the goal of obtaining meat for the community. Large complex projects have also been with us for a long time. The pyramids and the Great Wall of China were in their day of roughly the same dimensions as the Apollo Project to send man to the moon. We use the term project frequently in our daily conversations. A husband, for example may tell his wife, “My main project for this weekend is to straighten out the garage.” Going hunting, building pyramids, and fixing faucets all share certain features that make them projects.
A project has distinctive attributes, which distinguish it from ongoing work or business operations. Projects are temporary in nature. They are not an everyday business process and have definitive start dates and end dates. This characteristic is important because a large part of the project effort is dedicated to ensuring that the project is completed at the appointed time. To do this, schedules are created showing when tasks should begin and end. Projects can last minutes, hours, days, weeks, months or years.

Temporary does not necessarily mean the duration of the project is short. It refers to the project’s engagement and its longevity. Temporary does not typically apply to the product, service, or result created by the project; most projects are undertaken to create a lasting outcome. For example, a project to build a national monument will create a result expected to last for centuries. Projects can also have social, economic, and environmental impacts that far outlive the projects themselves.

Projects exist to bring about a product or service that hasn’t existed before. In this sense, a project is unique. Unique means that this is new, this has never been done before. Maybe it’s been done in a very similar fashion before but never exactly in this way. For example, Ford Motor Company is in the business of designing and assembling cars. Each model that Ford designs and produces can be considered a project. The models differ from each other in their features and are marketed to people with various needs.

Some people confuse the operation with projects; operations are ongoing and repetitive. They involve work that is continuous without an ending date and you often repeat the same processes and produce the same results. The purpose of operations is to keep the organization functioning while the purpose of a project is to meet its goals and to conclude. Therefore, operations are ongoing while projects are unique and temporary.
The project is completed when its goals and objectives are accomplished. It is these goals that drive the project and all the planning and implementation efforts are undertaken to achieve them.

Sometimes projects end when it’s determined that the goals and objectives cannot be accomplished or when the product or service of the project is no longer needed and the project is cancelled.