March_1970 — Page 32

swollen through contact with moisture embedded in the concrete. As they dried, the ropes shrank and were later ripped out by hand.

Spirals in the horizontal ribbed finish assist water run-off

the contractor to ensure constant spacing and true verticality of the rope during fixing. Horizontal lift marks were clearly defined by the use of small squared timber battens fixed to the formwork, producing a recessed joint.

After the concrete had initially hardened, the timber forms were struck, leaving the ropes which had

Strict time control

Experiment quickly showed the need for strict time control over the vibration of the concrete, the removal of the formwork and the subsequent

Rope lining is removed 24 hours after the formwork

pulling out of ropes. It was found that if the formwork was struck too soon, the ropes came away with them. If, on the other hand, they were pulled out too late, they became too strongly em- bedded for easy removal.

Eventually it was found that if the formwork was struck 24 hours after the concrete was placed, and the ropes pulled out 24 hours after that, no dif- ficults were experienced. It was also found that with care, both ropes and formwork could be re-used two or three times and that there was little, if any, need for making good the con- crete face.

The removal of the ropes leaves, of course, a vertically ribbed face. At the same time, the ripping out of the rope exposes the aggregate in the projecting ribs (with similar effect to hammer- ing), leaving the grooves comparatively smooth but with a clear impression of the helical twist of the rope.

The rope technique has been used in certain parts of the building inter- nally as well as externally, providing interesting textured effects for such concrete elements as structural mem- bers, hoist enclosures and reception desk fronts.

Architects for the hospital, which has been built for the United Liver- pool Hospitals, are The Anthony Clark Partnership and the structural en- gineers, Bingham Blades and Partners.

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Far East BUILDER, March 1970