In this article we will discuss about:- 1. Introduction to Giant Bamboo 2. Methodology for Producing Giant Bamboo 3. Properties of Bamboo Species in Philippines.
Introduction to Giant Bamboo:
Giant bamboo was the tallest, with the biggest internode diameter, the most number of internodes per culm next to kauayan-kiling, and the longest fibers. Buho was the shortest, with the smallest internode diameter and the least number of internodes per culm. Nevertheless, it yielded the longest internode and highest silica content. The different physical properties significantly differed among species, significant variation in specific gravity and tangential shrinkage.
Except for modulus of elasticity (MOE), the mechanical properties did not vary significantly among the six species. Height level showed significant variation in all mechanical properties except for MOE.
The natural distribution of bamboos encompasses mainly the tropical, sub-tropical mild temperate zones of the world, with tropical belt having the maximum number of bamboo species. Over 75 genera and 1,250 species are reported to occur in the world. By far, bamboo is among the most important forest products used by rural communities in the manufacture of cradle to housing components. The demand for this material has increased far beyond its availability, causing over-exploitation and depletion of resources.
The sobriquet “poor man’s timber” refers to bamboo. As a construction material, bamboo is potentially the most important non-timber forest product to replace wood for varied uses. Its strength, straightness, lightness combined with extraordinary hardness, range in size, abundance, easy propagation, and short period to attain maturity make it suitable for a variety of purposes and hundreds of uses. Even today, bamboo continues to find new applications such as in papermaking, rayon industry, construction, architecture, engineering, handicrafts, food and medicine.
Yet, little is known about this fascinating plant, its properties and other aspects which are receiving a high priority in the research pipeline of the Forest Products Research and Development Institute (FPRDI) based in College, Laguna. Thus, the physico-mechanical properties of some bamboo species were assessed to determine their potential uses in furniture, building and general construction work.
Methodology for Producing Giant Bamboo:
Five culms each of 3-year-old bamboo species, viz., bayog, bolo, buho, giant bamboo, kauayan-kiling and kauayan-tinik, were used in this study. Culm height, length, diameter and number of internodes per’ culm and culm wall thickness were determined. Representative sections of the butt, middle and top portions were cut into segments comprising of 8-whole length internodes. The segments and internodal sections were number-coded to indicate their original positions in the culm.
The methods used in determining moisture content, relative density and shrinkage were based on IS 6874, while those for compression parallel to grain and static bending were in accordance with the FPRDI method. Each 8-internodal section was further cut for use in the different tests, i.e. physical properties like moisture content, specific gravity and shrinkage (radial and tangential), and mechanical properties like maximum crushing strength (MCS), fiber stress at proportional limit (FSPL), modulus of rupture (MOR) and modulus of elasticity (MOE).
Statistical Analysis:
Data on the different physical and mechanical properties were analysed using CRD with sub-sampling. Significant properties were further subjected to Duncan’s Multiple Range Test (DMRT).
Properties of Bamboo Species in Philippine:
Table 1 shows the morphological data of six 3-year-old Philippine bamboo species, viz., culm height, number of internodes per culm, length and diameter of internodes and culm wall thickness.
Giant bamboo was the tallest at 21.4 m and buho the shortest at 8.6 m. Kauayan-kiling and giant bamboo exhibited the most number of internodes per culm (51 and 49 respectively), and bubo the least (16).
Buho and giant bamboo showed the longest internodes (51.6 cm and 42.9 cm respectively), the latter having the biggest internode diameter at 11.6 cm and the former the smallest at 5.2 cm.
In terms of culm wall thickness, bayog was the thickest especially in the basal part (1.9 cm) where it was sometimes observed to be almost solid. Bubo was the narrowest (0.5 cm).
The averages of the different physical and mechanical properties of the six erect bamboo species are given in Table 2. The summary of the ANOVA results on the physical and mechanical properties is shown in Table 3.
(a) Physical Properties:
DMRT results on the physical properties and height of the six erect bamboo species are shown in Tables 4 and 5.
Means with the same letter(s) are not significant at 0.05 probability level.
Means with the same latter(s) are not significant at 0.05 probability level.
(i) Moisture Content:
Buho registered the highest moisture content (173.71%) which was significantly different from the other species. However, no significant differences in moisture content were observed among the remaining species.
Generally, moisture content from the butt to the top of the culms decreased but not significantly (Table 5). This can be attributed to the thick-walled fibers and greater concentration of vascular bundles in the bamboo’s mature tissues. Another probable cause is the decrease in percentage of thin-walled parenchyma cells (the site of starch and water storage) on the culm top. This result conforms with the earlier findings of Liese (1987) and Abd. Latif and Mohd. Tamizi (1992).
(ii) Specific Gravity:
On the other hand, kauayan-tinik, kauayan-kiling and bayog showed the highest specific gravity values (0.644, 0.638 and 0.582 respectively) which significantly differed from the remaining species. Specific gravity significantly increased from the butt to the top. This can be due to the gradual increase in number and compactness of the fibrovascular bundles which contain more thick-walled fibers at the top.
(iii) Shrinkage:
Bubo exhibited the greatest radial (thickness) shrinkage at 18.73% and kauayan-kiling the highest tangential (width) shrinkage at 11.92%, which differed significantly from the other species. Radial and tangential shrinkages generally decreased from the butt to the top, and the decrease was significant for tangential shrinkage. The relatively higher frequency of fibrovascular bundles, low moisture content and high specific gravity in the thinner culm wall at the top may account for such reduction.
The dimensional changes from green to oven-dry condition sometimes, lead to collapse which appears merely as shrinkage and is frequently so interpreted. Collapse was observed in specimens obtained from the culms’ butt where there are more parenchyma cells and less fiber.
(b) Mechanical Properties:
DMRT results on the mechanical properties and height of the six erect bamboo species are shown in Tables 6 and 7.
Means with the same letter(s) are not significant 0.05 probability level.
Means with the same letter(s) are not significant 0.05 probability level.
(i) Maximum Crushing Strength:
MCS among the six bamboo species did not differ significantly from each other. Kauayan-tinik yielded the highest strength value of 42.14 MPa and buho the least at 30.13 MPa. However, MCS increased significantly from the butt to the top (33.07 to 44.30 MPa). The presence of nodes in the specimens not affect much the MCS, although, specimens taken from the middle internodes yielded higher MCS values than specimens from the nodal portions. At the nodal level, the fibers were considerably shorter than within the internode.
(ii) Stress at Proportional Limit:
SPL was not significantly different in all the species. Bayog showed the highest SPL value at 33.43 and giant bamboo the least at 13.76. FSPL at the butt (24.39) and top (27.30) significantly differed from the middle of the culm (18.04).
(iii) Modulus of Rupture:
MOR values were not significantly different from each other in all six bamboo species. Bayog had the highest MOR at 55.18 MPa and bolo the lowest at 23.69 MPa. Again, MOR at the butt (43.28 MPa) and top (42.44 MPa) were significantly different from the middle portion (31.12 MPa).
(iv) Modules of Elasticity:
MOE was significantly different in all the species, with kauayan-tinik and bolo registering the highest value (10.17 MPa and 10.06 MPa respectively) and giant bamboo the least (3.51 MPa) MOE significantly increased from the butt to the top. The mechanical elasticity at the nodal part decreases due to the presence of shorter, thicker and also forked fibers such that bamboo culms under tension often break at the node.
Density of bamboo, which is closely related to the relative proportions of fibrovasular bundle’s an ground tissue, greatly affects the bamboos’ physical and mechanical properties and this explains the increase in strength from butt to top of the culm.
Table 8 shows the fiber dimensions of the six erect Philippine bamboos, with giant bamboo having the longest fibers (3.8 mm), followed by buho (2.4 mm). Table 9 presents a summary of the six species’ chemical composition, while Table 10 outlines their recommended uses.
Conclusions:
Giant bamboo is the tallest of the six erect bamboo species studied. It has the biggest internode diameter, the most number of internodes per culm next to kauayan-kiling, and the longest fibers.
Buho is the shortest, has the smallest internode diameter and the least number of internodes per culm. Although, the thinnest in culm wall, buho has, the longest internode and highest silica content among the six species.
The average percentage moisture content in all species decreases toward the top but the trend is not significant.
The average specific gravity increases significantly towards the top.
The different physical properties significantly differ among species. Likewise, height level show significant variation in specific gravity and tangential shrinkage.
Generally, the mechanical properties do not vary significantly among the six species except for MOE. In height level, all mechanical properties except MOE are significantly different.