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Technological state-of-the-art
| Type of
form |
Dimensional
tolerances* of test piece after de-forming |
Flatness
tolerances* of test piece after de-forming |
Peso
della cassaforma vuota (Kg) Weight of empty form (Kg) |
Test
piece de-forming |
Transport
of forms |
| Steel |
Conforming |
Conforming |
30 Kg |
Easy |
Cumbersome
as enbloc |
| Polystyrene |
Not
always Conforming |
Not
always Conforming |
0,18 (single) |
Very
difficult |
Cumbersome
as enbloc |
| Polyurethane |
Conforming |
Conforming |
2,0 (single) |
Very
difficult |
Cumbersome
as enbloc |
* according to UNI EN 12390-1:2002 standards currently in
force.
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Disadvantages of classic forms
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|
Steel forms
Although they respect the dimensional and flatness tolerances of the
faces, they are very heavy (> 30 Kg) and, therefore, cannot be handled by one
person only in line with Italian Law decree No. 626 of 19th
September 1994 art. 47 and art.49. containing the “Regulations
on the safety and health of workers at work" and with Italian law
decree No. 494 of 14th August 1996,containing the "Minimum
prescriptions on safety and health to be applied in temporary or mobile
sites".
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Polystyrene
forms
Not only are they not easy to
de-form, but they also do not guarantee respect of the minimum dimensional
and flatness tolerances of the faces.
In fact, in most cases of test pieces packaged in this way, the faces must
first be ground or straightened out before the pieces are compression
tested. Furthermore, polystyrene forms have the additional disadvantage of
being 'single-use" and are not
disposable in the normal way. In fact, legal regulations on
polystyrene specify that it must be disposed of in special dumps.
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Polyurethane
forms
Although these forms respect the dimensional and flatness tolerances of
the faces, the method of removing
the test piece from the form is difficult.
There is a hole on the bottom of this type of form, which is covered
during filling, by a sheet of plastic or paper. The test piece is then
de-formed by overturning the form and using a compressed air pistol at about 2 Atm which is fitted in the hole on
the bottom.
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