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Joint failure

Originally conceived as a low technology floor construction method that needed no skilled labour, Pal-Kal has been popular with contractors relying on casual labour. Its basic weakness is the risk of a cold joint between the first 50mm of concrete poured and the rest of the concrete in the slab.

This first layer contains the main reinforcing mesh. Once the concrete is poured, inverted trough section corrugated steel void formers are pushed 10mm-15mm down into the hardening concrete before the rest of the concrete is poured and an upper layer of anti-crack mesh placed.

After a series of failures in shear along the cold joint, the system was modified to include hairpin shear links between the void formers close to the end supports, also pushed into the green concrete of the first layer. These modifications failed to convince the authorities that Pal-Kal could comply with Israeli building codes.

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