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3. Tanks for the storage of solids (silos)
3.1. Cement and clinker silos
3.1.1. Introduction
Silos for the storage of cement and clinker as a
rule are of cylindrical form, since this is the most
suitable for the frequently changing loads.
Beneath the actual storage space, the silos
normally have a trough for discharging the
contents and an access for loading transporting
equipment, as the silos are filled from the top but
emptied from the bottom.
Silos are usually comparatively large structures,
particularly in the vertical direction. Their walls are
therefore normally constructed with slipforming
and post-tensioned.
3.1.2. Clinker silos, Pedro Leopoldo, Brazil
Owner CIMINAS (Cimento Nacional de Minas
S.A.),
Sao Paulo
Engineer H. Trachsel & H. J. Schibli
AG, Olten, Switzerland
Contractor Joint venture M. Roscoe/
Moura, Schwark Ltda., Belo
Horizonte
Post-tensioning
Sistemas VSL Engenharia
S.A., Rio de Janeiro
Years of construction
1973-1974
Figure 113: Cable layout in the base slab
Introduction
Each of the two clinker silos has an internal
diameter of 26.00 m and a wall height of 42.00 m.
The wall thickness is 320 mm. The base slabs,
which each rest on 232 piles, are 1.70 m thick
(Fig. 112). The distance between the centres of
the silos is 32.00 m.
Construction procedure
The silo walls were constructed by slipforming.
During slipforming only timber.
formwork strips with the anchorages fixed to them
and the empty ducts were placed. Construction of
the first wall lasted 9 days and that of the second
7 days.
Post-tensioning
Each base slab was post-tensioned with 144 VSL
cables EU 5-12 in 2 layers. The first layer is
located 400 mm above the lower face of the
foundation slab and the second 400 mm below
the upper face. The cables are curved at their
ends, in order to lead the cables axes radially from
the edge of the slab. In the central region of the
slab the cables cross one another. Cable lengths
vary from 25.50 to 31.50 m (Fig. 113).
The silo wall is horizontally post-tensioned with
104 VSL cables EE 5-12 and 55 cables EE 5-7.
The cables each extend around one-half of the
circumference. They are anchored alternately at
the four buttresses. The cables were pulled into
the empty ducts by working from a suspended
scaffold (Fig. 114). The cable axis is 100 mm from
the outer face of the wall. The cable spacing is
220 mm minimum and 810 mm maximum.
3.1.3. Cement silos, Chekka, Lebanon
Owner Societe des Ciments
Libanais, Chekka
Engineer H. Trachsel & H. J. Schibli
AG, Olten, Switzerland
Heinzelmann & Co. AG,
Brugg, Switzerland
Contractor R. Fakhry, Beirut
Slipforming
and Post-tensioning
VSL INTERNATIONAL LTD.,
Berne, Switzerland
Years of construction
1974-1975, 1977-1978,1981
Figure 112: Cross-section through a silo
Figure 114: Susperidea scaffold for
post-tensioning operations
Introduction
The cement factory of Chekka is approximately 60
km to the north of the Lebanese capital of Beirut
close to the shore of the Mediterranean. From
1974 to 1978 the plant was extended and five new
cement silos were built (Fig. 115). The
construction time for the extension was originally
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