Re-use of casting timber could be a way of saving timber resources, particularly in countries where most timber for construction purposes has to be imported. The objective of the present study was to investigate residual concrete on casting timber re-used five times. Moulds were made of sections of Norway spruce, untreated and treated with a casting oil and a wax formulation applied by a vacuum-pressure process, respectively. Casting was carried out with concrete of strength class C40/50 with a slump of 120 mm. The concrete was allowed to set for at least ten days before the sections were investigated with respect to residual concrete. None of the treatments, wax applied by vacuum pressure treatment or casting oil applied by brushing, resulted in completely residual free wood surfaces after five castings. The best result was obtained with the casting oil. If application by vacuum-pressure ever shall be an attractive alternative to the superficial treatment with casting oil, further improvements of the treatment formulation are necessary. It is hardly realistic to completely avoid residues, but re-use of the casting timber five times should be possible if the residues can be minimized and some scraping can be accepted.

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