Jointing

The techniques used to seal joints in GRC components or panels are similar to those used for precast concrete or GRR There are essentially four main ways of dealing with joints:

- gaskets;

- baffles in an open-drained joint;

- face sealants;

- cover strips.

Gasket joints

Gaskets are effective only where positive pressure is available to deform or compress them. A typical joint incorporates a top-hat section with captive nut to pull back a metal cover strip against a neoprene gasket. Advantage can be taken of the quality of the edge profile, which is normally possible in GRC, to use push-in fir-cone gaskets, as used, for example, at the UOP Fragrances factory (architects: Piano and Rogers) (Fig. 4.6). These gaskets incorporate barbed legs, which can be pushed into position in the joint. One problem in using such gaskets is that the moulded GRC nibs to receive the gasket have only one mould face, and however well the back face is compacted, minor variations in thickness will occur, which can cause points of weakness for an effective weatherproof seal. These nibs can be wrapped in tape to take up any tolerances in surface defects resulting from manufacture, in order to gain a tight fit before applying the compression gasket.The UOP Fragrances factory also used a push-in gasket on the inside face; some difficulty may be experienced in sealing past the adjustable clamps in such a detail.

4.6 Gasket joint at UOP Fragrances factory showing insulation core foamed between skins.

Another problem with gasket joints Is that they depend upon extremely tight tolerance in joint size, and may only really work in conjunction with a system of adjustable fixing devices. Typical permissible joint range clearances are 5-10 mm. The use of slotted holes and T-clamps at UOP Fragrances resulted in precise location of panels, allowing the use of this method of gasket jointing even at the corner detail. Direct glazing of windows into GRC is also possible using neoprene gaskets.

Was this article helpful?

0 0

Post a comment