Agriculture Reference
In-Depth Information
a radically different behaviour. The material
can undergo considerable change in shape
without rupturing. For the mixtures tested, and
depending on the proportion of binding agent,
an intermediate range of behaviour is seen.
This ability to distort without breaking confers
a springiness upon the material and an ability
to accommodate movement and resist any ten-
dency to crack. It is therefore necessary that
the right rendering be chosen carefully, so
that this property is demonstrated in a surface
that can also resist deterioration.
The significant porosity of concrete asso-
ciated with a binding agent of moderate resist-
ance results in weak resistance to compression:
Rc between 0.1 and 2.5 MPa, depending on
the binder used and in what proportion
(Fig. 17.8). These values are not adequate to
allow the construction of weight-bearing ele-
ments of standard dimensions.
If we now consider the tensile properties
as measured by a flexion test and illustrated in
Fig. 17.9, once again the suppleness of the mater-
ial is demonstrated, allowing for considerable dis-
50
Tile-Rc
40
Roof-Rc
30
Hemp-Rc
20
Binder A-Rc
10
0
0
50
100
150
200
250
Displacement (mm)
Fig. 17.7.
Resistance to compression trials. The initial height of the sample is 32 cm, actual height
16 cm. Graph showing the relative changes. (Rc = resistance to compression.)
RATIO HEMP/BINDER
(in mass)
1,4
1,2
0.21
0.28
0.39
1
0,8
0.42
0.41
Wall
0,6
Floor
0.49
0,4
0.55
0.58
0,2
Roof
1.02
0
0
5
10
15
20
25
TIME (months)
Fig. 17.8.
Evolution of the resistance of hemp fibre to compression over time and as a function of the
proportion of hemp to binder by mass.
