Plastiline™ - Humes

9 Incorporation of keyed Plastiline
in cast insitu concrete structures
9.1 The Plastiline must cover the areas specified and is
secured to the inner formwork face prior to placing the
concrete and reinforcement. Formwork used must be
suitable for proper attachment of the plastic sheet.
The preferred method of attachment of the sheet is by
nailing or stapling directly to timber forms, or to timber
nailing strips set in steel forms at the appropriate
positions. Nails shall be of approved small flat-headed
type. All fasteners must be placed within 7mm of the edge
of the sheet so that holes will be covered by the welding
strip. If it is necessary to secure a joint flap a temporary
form support must be used and the flap must be fastened
within 7mm of its edge.
Alternatively, it can be held to steel forms by light metal or
plastic bands tightened on to suitable attachments to the
forms. Provision must be made to maintain the sheet in
close contact with the form during concrete placement.
Bands must be of the type recommended by Humes.
If the bands cross the keys, provision must be made to
ensure that the keys are not bent or distorted.
All pipe or other metal inserts must be held firmly in place
on the formwork and, where required, the Plastiline
protection of these inserts must first be installed. Metal
form ties shall be kept to a minimum.
9.2 In the case of large floors or the bottoms of large
tanks etc the alternatives are:
i) Where there is no external hydrostatic head or other
potential uplift, plain Plastiline sheet or blankets can be
loose-laid or bonded to the base slab with an adhesive
approved by Humes.
ii) Where the base can be subject to pressure from
external ground water, Plastiline should be embedded
into the top of the slab, using a vibrating screed. This
vibrator is applied after bleeding has ceased, but before
initial set occurs.
As it is essential to insert the keys before the concrete
hardens, it may be necessary to limit the area of each pour.
iii) After vibrating the Plastiline into position, if
sheets/blankets overlap, care must be taken to ensure
concrete mortar is cleared from welding areas prior to the
complete hardening of the concrete.
9.3 Unless otherwise specifically indicated, Plastiline
blankets shall be positioned so that the locking keys are
vertical or as near vertical as possible to provide a free
escape to the bottom of fluid which may accumulate
between the lining and wall of the structure. Where the
locking keys cannot be positioned vertically a gap of
between 75mm and 100mm width shall be provided by
cutting off the locking keys at intervals not greater than
2.5m longitudinally, to provide weep channels. A weep
channel shall be provided approximately 300 mm away
from all lining returns.
Where changes in direction or corners are encountered, the
Plastiline may be bent and secured to the form, provided
the radius of the blend is not less than 25mm.
Where sharper corners are specified, a jointing method
approved by Humes must be used.
9.4 For lining joints which do not correspond to joints
in the concrete structure, the Type C3 joint is preferred. For
this joint the Plastiline sheets are butted together,
so that the gap between sheets and/or blankets at
any position does not exceed 4mm. This gap must be
temporarily sealed by a wide PVC tape before placing
concrete. After form removal a flat welding strip, centred
over the gap, is welded to give a permanent and
continuous lining on the inside of the structure.
As an alternative, the lap joint Type C2 may be used.
This joint requires that the Plastiline be lapped at least
35mm, the overlap or flap being on the downstream side
of the joint. A Type C2 joint must be at longitudinal
construction joints in concrete structure.
For Plastiline lining joints at transverse construction or
contraction joints in the concrete structure, a Type C1 joint
must be used.
Normal jointing method C1
This is identical with type P1
Normal jointing method C2
Note: Type C1 Joint is identical with type P1
Min. overlap 35mm
Flat Welding Strip
Direction of flow
PVC Tape
Use seam weld or apply pvc
tape before placing concrete.
Method of jointing Plastiline in structure without joint.
Not to be used where transverse construction or
contraction joint occurs. Shall be used where a
longitudinaL construction joint intersects with a joint
in the Plastiline.
Normal jointing method C3
Apply welding strip after stripping formwork
Plastiline
Method of jointing sheet, except where construction or
contraction joint occurs, should be used when longitudinal
construction joint intersects with a joint in the Plastiline.
Shall not be used where transverse construction or
contraction joint occurs.
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