Synopsis
Friction and adhesion between concrete and form surfaces during the first hours of contact determine the shifting process in slip-form technology and are also of interest in processes involving immediate stripping and in the transportation of ready-mixed concrete. Experimental data are presented on the behaviour of hardening mortar (as a part of concrete obviously coming in contact with mould surfaces) with different mould materials in terms of friction and normal and tangential adhesion, including the aspect of surface cleanliness. These results make it possible to determine the forces required for overcoming adhesion in normal and tangential shifting of the form, and to recommend facing or coating agents for slip-form panels. The results, obtained in small laboratory tests, were then checked by casting 0·15 × l·0 × 2·5 m wall panels in a part of a slip-form.
