Proceedings e report - Firenze University Press

COLLAPSE RECONDITIONING OF EUCALYPTUS CAMALDULENSIS DEHN FROM ALGERIA
(a) (b)
(c) (d)
Fig. 2: Measurement of shrinkage
(a) Measurement points for shrinkage on 3 faces (TR, TL and RT), (b) Experimental set up,
(c) Experimental device for shrinkage measuring, (d) Autoclave for reconditioning of specimens
The partial shrinkage (expressed in %) is calculated before reconditioning by the following
expression:
RXS = (LXs-LX12) / LXs (4)
where X stands for the direction (L, R or T), LXs is the average specimen length in the saturated state,
LX12 in the air-dry state. The total shrinkage is any direction X is defined as:
RXT = (LXs-LX0) / LXs (5)
Volumetric shrinkage is noted by replacing X by V and calculated by the following expressions:
RVy=1-(1-RTy) (1-RRy) (1-RLy) (6)
where y stands for S (partial) or T (total). Shrinkage anisotropy is calculated as:
RRy / RTy (7)
Coefficients of shrinkage are also calculated. They are obtained for any direction X by dividing the
partial shrinkage by the estimated loss of bound water:
CRXS = RXS / (Hs-H12) (8)
where H12 is the m.c. of the specimen measured in air-dry condition and Hs the moisture content at
fibre saturation point, given arbitrarily the typical value of 30%.
Having been re-conditioned under vaporization at 110°C during 20 minutes in autoclave, the
specimens were ovendried, which allows to compare the shrinkage before and after reconditioning.
Measurements in air-dry state in 3 directions and for the same length measured before reconditioning
were done again; the same expressions were applied to calculate the tangential, longitudinal, radial and
volumetric shrinkages as well as the transverse anisotropy. Partial shrinkage after reconditioning,
corresponding to wood presumably without collapse, is noted RXC for any direction X (L, R, T and
V) and obtained in the same way as the partial shrinkage before reconditioning, as well as shrinkage
anisotropy RRC/RTC. The reconditioning fraction is defined as the ratio of shrinkage with collapse to
that without collapse:
RXS / RXC (9)
It is expected to be always superior to 1.
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