Abstract :
Bamboo is subject to attack by microorganisms and
insects in almost any construction applications. The decay and biodegradation
of bamboo culms during outdoor storage can be checked to a great extend by
adopting a good storage yard practices. Culms should be stacked horizontally
over raised wall to facilitate water drainage and air circulation. For reed
bamboos, vertical stacking results in a small gain in pulp yield over
horizontal stacking because the former suffers less fungal damage. The service
life of bamboo is therefore, mainly determined by the rate of attack. A variety
of methods to improve the durability of bamboo have however, been developed.
Basically, there are two methods for increasing the durability of bamboo.
TENSILE STRENGTH
Bamboo is able to resist more tension than
compression. The fibres of bamboo run axial. In the outer zone are highly
elastic vascular bundle, that have a high tensile strenght. The tensile
strenght of these fibres is higher than that of steel, but it’s not possible to
construct connections that can transfer this tensile strength. Slimmer tubes
are superior in this aspect too. Inside the silicated outer skin, axial
parallel elastical fibers with a tensile strength upto 400 N/mm2 can be found.
As a comparison, extremely strong wood fibers can resist a tension upto 50 N
/mm2.
COMPRESSIVE STRENGTH
Compared to the bigger tubes, slimmer ones have got,
in relation to their cross-section, a higher compressive strength value. The
slimmer tubes possess better material properties due to the fact that bigger
tubes have got a minor part of the outer skin, which is very resistant in
tension. The portion of lignin inside the culms affects compressive strength,
whereas the high portion of cellulose influences the buckling and the tensile
strength as it represents the building substance of the bamboo fibers.
ELASTIC MODULUS
The accumulation of highly strong fibers in the
outer parts of the tube wall also work positive in connection with the elastic
modulus like it does for the tension, shear and bending strength. The higher
the elastic modulus, the higher is the quality of the bamboo. Enormous
elasticity makes it a very useful building material in areas with very high
risks of earthquakes.
Anisotropic
Bamboo is an anisotropic material. Properties in the
longitudinal direction are completely different from those in the transversal
direction. There are cellulose fibers in the longitudinal direction, which is
strong and stiff and in the transverse direction there is lignin, which is soft
and brittle.
SHRINKAGE
Bamboo shrinks more than wood when it loses water.
The canes can tear apart at the nodes. Bamboo shrinks in a cross section of
10-16 % and a wall thickness of 15-17 %. Therefore it is necessary to take
necessary measures to prevent water loss when used as a building material.
FIRE RESISTANCE
The fire resistance is very good because of the high
content of silicate acid. Filled up with water, it can stand a temperature of
400° C while the water cooks inside.
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