The Bamboo Reinforced Concrete Construction
Nowadays bamboo used in Portland cement as reinforcement. Though bamboo had been used as construction material for many years in different countries. But now the usage of bamboo has got importance in Clemson study.
In 1964 U.S. army engineer studied about the chances to use bamboo as construction material in precast concrete elements. For estimating the load carrying capacity of precast concrete elements with use of bamboo reinforcing, procedures of strength design were used. Now usage of bamboo was given paramount importance for reinforcement in soil cement pavement slab in where slabs behaved as non-elastic even under light weight.
Using of bamboo is way more affordable and easier to use.
Selection of Bamboo
1. Users have to use only those types of bamboo which already showed a brown color. The bamboo plant must be 3 years old.
2. Users have to select longest large diameter culms.
3. Users must not use whole part of green unseasoned bamboo.
4. They must avoid to cut the bamboo in spring or early summer. This time fiber of bamboo is weaker because of fiber moisture content.
Preparation of Bamboo
Sizing: Splints are more suitable than whole culms as reinforcement. Larger shaped culms must be split approx. ¾ inch wide. Whole culms less than ¾ in diameter can be used also.
Seasoning: Users have to cut and dry the bamboos for three to four weeks before using. The culms should be helped to reduce warping.
Bending: If users apply heat, dry or wet then bamboo can be permanently bent. This procedure is used to form splints into C shaped stirrups and to put hooks on reinforcement.
Waterproof Coating: Seasoned bamboo should coated with waterproof thing for reducing swelling in contact with concrete. Without any coating bamboo can be swell before concrete got the sufficient strength for preventing crack. Type of coating is depending upon the material. Brush coat or dip coat of asphalt emulsion is good for this. Apart from this native latex, coal tar, paint, dilute varnish and also water glass are also suitable coating.
Principles of Construction
The Mix Proportion of Concrete
This mix designs can be used as with steel reinforce concrete. Concrete ebb should remain a certain up to amount as per workability will allow. Excess water causes swelling in the bamboo. High early strength cement should be used to minimize the crack caused by swelling.
Reinforcement of bamboo must not be placed less than 1 to ½ inches from the concrete surface. While using whole culms, the top and bottom part of the stems must be changed in every row. The space between bamboo rods must not be less than ¼ inch. Reinforcement must be lashed together on small sticks. It should be placed at right angle to the main reinforcement. More than one layer must be tied together. Tied should be made with wire.
Bamboo must be tied down before placing the concrete. It must be fixed between 3 to 4 feet for preventing it to float up in concrete during placement and vibration. The extra diagonal tension reinforcement must be used. The vertical stirrups can be made from wire. It also can be improvised from the split section of the bamboo and bent into u shaped. It must be tied to both bottom longitudinal and bent up reinforcement.
Bamboo reinforced concrete design is similar to the design of steel reinforcement. Bamboo reinforcement must have this below mentioned mechanical properties.
|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||2.5x106|
1. Flexural members can be reinforced with bamboo can be designed.
2. Longitudinal reinforcement of bamboo must be between 3 to 4 percent of the concrete cross section.
3. In bamboo reinforced beam curve supplied cross sectional dimensions. The cross-sectional dimensions have same bending moment resistance.
4. The curves must be drawn for 3 percent of concrete cross section as bamboo reinforcement. this remains in good range for flexural members.
5. A particular number of rods must be used for providing adequate spacing.