Bamboo Reinforcement in Portland Cement Concrete - GLENN H. E. 1950

[Mark Meckes]

From the publication:
Bamboo as a Building Material - by F. A. McClure - May 1953
Foreign Agricultural Service - United States Department of Agriculture

In the section:

Bamboo Reinforcement of Concrete - Pg 7 - 11

Published references to the use of bamboo in reinforcing cement concrete structures or parts thereof indicate that the practice has been followed for some decades at least, in the Far East (China, Japan, and the Philippine Islands).
During the 1930's several experiments were carried out in Europe, particularly in Germany and Italy, to test the performance of cement concrete beams reinforced with bamboo.
The most recent, comprehensive, and readily available information on the subject is to be found in the report of a series of experiments carried out by and under the direction of Professor H. E. Glenn.
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GLENN H. E. 1950. Bamboo Reinforcement in Portland Cement Concrete. Eng. Expt. Sta., Clemson College, Clemson, South Carolina, Eng. Bull. No. 4.
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Two important sections are quoted here in entirety. - F. A. McClure

Summary of Conclusions From Results of Tests on Bamboo Reinforced Concrete Beams

Below is given a summary of the conclusions as indicated from results of tests on the various beams included in this study.

1. Bamboo reinforcement in concrete beams does not prevent the failure of the concrete by cracking at loads materially in excess of those to be expected from an unreinforced member having the same dimensions.

2. Bamboo reinforcement in concrete beams does increase the load capacity of the member at ultimate failure considerably above that to be expected from an unreinforced member having the same dimensions.

3. The load capacity of bamboo reinforced concrete beams increased with increasing percentages of the bamboo reinforcement up to an optimum value.

4. This optimum value occurs when the cross-sectional area of the longitudinal bamboo reinforcement was from three to four percent of the cross-sectional area of the concrete in the member.

5. The load required to cause the failure of concrete beams reinforced with bamboo was from four to five times greater than that required for concrete members having equal dimensions and with no reinforcement.

6. Concrete beams with longitudinal bamboo reinforcement may be designed to carry safely loads from two to three times greater than that expected from concrete members having equal dimensions with no reinforcement.

7. Concrete beams reinforced with unseasoned bamboo show slightly greater load capacities than do equal sections reinforced with seasoned untreated bamboo. This statement was valid so long as the unseasoned bamboo had not dried out and seasoned while encased in the concrete when the load was applied.

8. When unseasoned untreated bamboo was used as the longitudinal reinforcement in concrete members, the dry bamboo swelled due to the absorption of moisture from the wet concrete, and this swelling action often caused longitudinal cracks in the concrete, thereby lowering the load capacity of the members. These swell cracks were more likely to occur in members where the percentage of bamboo reinforcement was high. This tendency was reduced by the use of high early strength concrete.

9. The load capacity of the concrete members reinforced with bamboo vary with the dimensions of the members.

10. The unit stress in the longitudinal bamboo reinforcement in concrete members decreased with increasing percentage of reinforcement.

11. The ultimate tensile strength of the bamboo in bamboo reinforced concrete members was not affected by changes in the cross-sectional area of the members so long as the ratio of breadth to depth was constant but was dependent on the amount of bamboo used for reinforcement.

12. Members having optimum percentage of bamboo reinforcement (between three and four percent) are capable of producing tensile stresses in the bamboo of from 8,000 to 10,000 pounds per square inch.

13. In designing concrete members reinforced with bamboo, a safe tensile stress for the bamboo of from 5,000 to 6,000 pounds per square inch may be used.

14. Concrete members reinforced with seasoned bamboo treated with a brush coat of asphalt emulsion developed greater load capacities than did equal sections in which the bamboo reinforcement was seasoned untreated or unseasoned bamboo.

15. When seasoned bamboo treated with a brush coat of asphalt emulsion was used as the longitudinal reinforcement in concrete members, there was some tendency for the concrete to develop swell cracks, especially when the percentage of bamboo reinforcement was high.

16. Care should be exercised when using asphalt emulsion as a waterproofing agent on seasoned bamboo as an excess of the emulsion on the outer perimeter of the culm might act as a lubricant to materially lesson the bond between the concrete and bamboo.

17. Concrete members reinforced with unseasoned sections of bamboo culms, which had been split along their horizontal axes, appeared to develop greater load capacities than did equal sections in which the reinforcement consisted of unseasoned whole culms.

18. Concrete members reinforced with seasoned sections of bamboo culms, which had been split along their horizontal axes and treated with a brush coat of asphalt emulsion, developed considerably higher load capacities that did equal sections in which the reinforcement was split sections of seasoned untreated bamboo.

19. When split sections of seasoned untreated large diameter culms were used as the reinforcement in a concrete beam, longitudinal cracks appeared in the concrete due to the swelling action of the bamboo. This cracking of the concrete was of sufficient intensity as to virtually destroy the load capacities of the members.

20. When unseasoned bamboo was used as the reinforcement in a concrete member, the bamboo seasoned and shrank over a period of time while encased in the concrete. This seasoning action of the bamboo materially lowered the effective bond between the bamboo and concrete with a lessening of the load capacities of the members.

21. Increasing the strength of the concrete increases the load capacities of concrete members reinforced with bamboo.

22. Concrete members reinforced with seasoned bamboo treated with methylolurea did not develop greater load capacities than did equal sections in which the bamboo reinforcement was seasoned culms treated with a brush coat of asphalt emulsion.

23. The load capacities for concrete members reinforced with unseasoned, seasoned or seasoned and treated bamboo culms, were increased by using split bamboo dowels as the diagonal tension reinforcement along the sections of the beams where the vertical shear was high.

24. The load capacities for concrete members reinforced with unseasoned, seasoned or seasoned and treated split sections of bamboo were increased by the use of a combination of split dowels and the bending up of the upper rows of the split bamboo from the bottom of the beam into the top and covering sections of the beams where the vertical shear is high.

25. Ultimate failure of bamboo reinforced concrete members usually was caused by
diagonal tension failures even though diagonal tension reinforcement was provided.

26. A study on the deflection data for all the beam specimens tested indicated:

(a) That the deflections of the beams when tested followed a fairly accurate straight line variation until the appearance of the first crack in the concrete.

(b) Immediately following the first crack, there was a pronounced flattening of the deflection curve (probably due to local bond slippage) followed by another period of fairly accurate straight line variation, but at a lesser slope, until ultimate failure of the member occurred. This flattening of the deflection curve was more pronounced in the members where the amount of longitudinal bamboo reinforcement was small.

(c) In all cases noted, the deflection curve had a lesser slope after the appearance of the first crack in the concrete, even though high percentages of bamboo reinforcement were used.

27 No pronounced variations were observed when the behavior of bamboo reinforced concrete members under flexure and having "tee" sections was compared with that of equal members having rectangular sections.

28 Bamboo reinforced concrete members under flexure and consisting of "tee" sections were no more effective than were equal rectangular sections, provided the breadth of the stem of the "tee" section was equal to that of the rectangular section and the effective depth of both were the same.

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Design and Construction Principles Recommended for Bamboo Reinforced Concrete

(Will add this info soon)

Mark