04-08-2012, 12:03 PM
Bamboo in Construction: An Introduction
Bamboo in Construction.pdf (Size: 1.88 MB / Downloads: 351)
Introduction
Bamboo has a long and well established tradition as a
building material throughout the world’s tropical and
sub-tropical regions. It is widely used for many forms of
construction, in particular for housing in rural areas.
Bamboo is a renewable and versatile resource,
characterised by high strength and low weight, and is
easily worked using simple tools. As such, bamboo
constructions are easy to build, resilient to wind and
even earthquake forces (given the correct detailing)
and readily repairable in the event of damage. Associated
products (bamboo based panels and bamboo
reinforced concrete, for example) also find applications
in the construction process.
Protection of bamboo
Natural durability
As with all timbers, the service life of bamboo is
governed by its exposure position and durability, which
together dictate the rate of attack by biological agents.
In general it has been found that untreated bamboo
has an average life of l-3 years where it is directly
exposed to soil and atmosphere. When used under
cover, the life expectancy of bamboo increases to 4-7
years. Under very favourable circumstances, the
service life of bamboo can be as high as 10-I 5 years,
for example when used for rafters and internal framing.
The chemical constituents of bamboo are known to
vary greatly depending on species, position within the
culm and the age of the culm. In very general terms
bamboo consists of 50-70% hemicellulose, 30%
pentosans, and 20-25% lignin (Tamolang et al. 1980,
Chen et al. 1985). 90% of the hemicellulose is xylan
with a structure intermediate between hardwood and
softwood xylans (Higuchi, 1980). The structure of the
lignin present in bamboo is unique, and undergoes
changes during the elongation and ageing of the culm
(Itoh et al. 1981). Bamboo is known to be rich in silica
(0.5-4%), but almost the entire silica content is located
in the epidermis layers, with hardly any silica in the rest
of the wall. Bamboo also has minor amounts of resins,
waxes and tannins. However, none of these have
sufficient toxicity to impart much natural durability to the
culms. Laboratory tests have indicated that bamboo is
more prone to both soft rot and white rot attack than to
brown rot (Liese, 1959).
Preservation of bamboo
Bamboo is subject to attack by micro-organisms and
insects in almost any construction application. Unfortunately,
like most lignocellulosic materials, bamboo has
very low resistance to biological degrading agents The
service life is therefore mainly determined by the rate of
attack.
A variety of methods to improve the durability of
bamboo have, however, been developed. Several of
these techniques are described here with the aim of
providing helpful guidelines to users.