| 摘要 |
<p>Concrete units for wall facing plates, slabs, building plates and purlins resistant to rain water and temps below freezing, are made by (a) casting concrete, if necessary with vibration, in a mould with a smooth surface using a comparatively rich mixture and fine-grained additives (a) at least in area near the smooth surface, (b) leaving concrete unit in mould for 1-5 (2-4) days so that the surface layers of the unit lying by the smooth mould wall are hardened to an extent such that they can be lifted from mould surface without leaving marks and (c) coating the concrete unit surface cast near the smooth mould wall with a hard, vitreous, weatherproof plastic layer. Pref. mould surface is made of glass, plastic such as polyvinyl chloride, silicone rubber, acrylic, polyester, polystyrene or polyethylene plastic or a polished metal inert to cement. Pref. plastic coating consists of epoxy resin, silicone polyester, acrylic or polyurethane plastic, more pref. admixed with a pigment or metal powder such as Cu, Al or alloy, such as Cu bronze.</p> |
