Bamboo Reinforcement

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  • 2. CONTENT • Overview Of Bamboo • General Characteristics Of Bamboo • Selection • Seasoning • Bending • Sizing • Concrete Mix Proportions • Placement Of Bamboo • Mechanical Properties Of Bamboo • Comparison Of Bamboo And Steel • Conclusion
  • 3. Overview Of Bamboo  Basically bamboo is a perennial grass belonging to the class monocotyledonous, and is approximately almost 600 species recorded throughout the world .  Several countries did research on bamboo reinforcement and have noticed that the major advantage of bamboo lie in it relatively high tensile strength .  The principal problems associated with bamboo reinforcement are bond, volume change and possibly decay .  So, there should be further research concerning bond mechanisms, means of improving bond strength, methods of controlling volume changes, decay and the behavior of bamboo under loadterm of repeated load .  Bamboo was given recent consideration for use as reinforcement in soil cement pavement slabs in which the slabs behave inelastically even under light loads .
  • 4. General characteristics of Bamboo • The specific gravity of bamboo varies between 0.4 and 0.5 . • The ratio of tensile strength to specific weight of the bamboo is about 6times that of steel • The strength of bamboo is high in parallel direction to the grains and less in perpendicular direction . Selection The following factors should be considered in the selection of bamboo culms(whole plants) for use as reinforcement in concrete structures .  Use only bamboo showing a pronounced brown color. This will insure that the plant is at least three years old  Select the longest large diameter culms available .  Do not use whole culms of green, unseasoned bamboo .  Avoid bamboo cut in spring or in early summer. These culms are generally weaker due to increased fiber moisture content .
  • 5. Seasoning Bending When possible, the bamboo should be cut and allowed to dry and season for three to four weeks before using. The culms must be supported at regular spacings to reduce warping. Bamboo can be permanently bent if heat, either dry or wet, is applied while applying pressure. This procedure can be used for forming splints into Cshaped stirrups and for putting hooks on reinforcement for additional anchorage.
  • 6. SIZING Splints(split culms) are generally more desirable than whole culms as reinforcement . Larger culms should be split into splints approximately 3/4 inch wide . Whole culms less than 3/4 inch in diameter can be used without splitting . Splitting the bamboo can he done by separating the base with a sharp knife and then pulling a dulled blade through the culm. The dull blade will force the stem to split open; this is more desirable than cutting the bamboo since splitting will result in continuous fibers and a nearly straight section. Whole Culms The following table shows the approximate Diameter (in.) Area (sq. in.) net area provided by whole culms and by 3/8 0.008 3/4-inch-wide splints . 1/2 0.136 5/8 0.239 3/4 0.322 1 0.548 2 1.92
  • 7. Concrete Mix Proportions  The same mix designs can be used as would normally be used with steel reinforced concrete .  Concrete slump should be as low as workability will allow .  Excess water causes swelling of the bamboo .  High early-strength cement is preferred to minimize cracks caused by swelling of bamboo when seasoned bamboo cannot be waterproofed.
  • 8. Placement Of Bamboo  Bamboo reinforcement should not be placed less than 1½ inches from the face of the concrete surface .  The clear spacing between bamboo rods or splints should not be less than the maximum size aggregate plus ¼ inch .  Reinforcement should be evenly spaced and lashed together on short sticks placed at right angles to the main reinforcement .  The ties can be maid with vegetation strips .  This embedded depth is approximately 10 times the diameter of whole culms or 25 times the thickness of ¾ inch wide splints .  Spacing of the stirrups should not exceed 6 inches .
  • 9. Design Principles Bamboo reinforced concrete design is similar to steel reinforcing design. Bamboo reinforcement can be assumed to have the following mechanical properties. Mechanical Properties Of Bamboo 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 x 10^6
  • 10. Comparison of Bamboo And Steel  The strength of bamboo is greater than steel .  Bamboo is easily accessible .  Bamboo lowers the cost of construction .  Increases the strength of the buildings .  Bamboo can crack and deflect more than steel reinforcement .
  • 11. Conclusion  The environmental and financial comparison demonstrates that bamboo can compete with building material.  Bamboo is a natural product and will therefore always have some extent of irregularity  It is therefore suggested that the bamboo culm should be used in functions were the measurement requirements are not entirely precise or fixed, as in temporary buildings (e.g., pavilions and tents) or small civil projects.  Furthermore, bamboo can play a role as a non-supporting or finishing material.