283757893275

Cladding and Curtain Wall Construction 445
Structural
frame
Concrete
floor
Figure 7.26 Storey height precast cladding units.
Storey height
cladding units
with windows
Surface finishes
To provide an acceptable finish to the exposed faces of precast concrete panels, it is usual
practice to provide what is sometimes called an ‘indirect finish’ by abrasive blasting, surface
grinding, acid washing or tooling to remove the fine surface layer and expose the aggregate
and cement below. This surface treatment has the general effect of exposing a surface of
reasonably uniform colour and texture. This form of surface treatment can produce a fine
smooth finish by light abrasive sand or grit blasting or grinding, or a more coarse texture
by heavy surface treatment.
Applied finishes
Any type of brick that is reasonably frost resistant and durable may be used as a facing
material and fixed to the precast concrete panels using the mould to produce the full range
of brick construction features such as corbels, string courses, piers and arches. The facing
brickwork is bonded to the concrete panel either with a mechanical key or by stainless steel
or nylon filament ties. A mechanical key can be provided where bricks with holes in them
are used and cut along the length of the brick, so that the resulting semicircular grooves
may provide a bond to the concrete. To ensure a good bond to the bricks, it is essential to
saturate the bricks thoroughly before the backing concrete is placed. Where ties are used
to retain the face bricks in place, the nylon filament, stainless steel wire or bars are threaded
through holes in the brickwork and turned up between bricks as loops to bond with the
backing concrete.
Applied finishes of brick or stone to precast concrete cladding panels are less used than
they were because of the considerable costs of casting, transporting and lifting into place