Method and plant for manufacture of cementitious products

摘要

A plant and method for the manufacture of cementitious products, viz. cast concrete roof tiles (T) are disclosed. A cementitious composition comprising water, sand, pigment, flyash, cement and additives, is admixed in mixing station 2 and fed into re-usable moulds 6 to form greenstate building products (e.g. tiles), which are cured and demoulded. The products T are conveyed through a surface preparation zone 12 where upper surfaces of the products are prepared (e.g. by application of a primer) followed by coating of the prepared surface. The constituents of the composition are admixed under atmospheric pressure and further mixed under a partial vacuum of 200 to 340 m Bar after addition of an entrainment agent. The tiles are cured in a conventional autoclave for up to 10 hours at 45 degrees C. The primer coat maybe a water based epoxy. The admixed cementitious composition has a Ford Cup flow of between 40 and 60 seconds and a slump test of between 180 and 220 mm. In an alternative method, instead of applying a primer coat, the upper surfaces, in use, of the roof tiles T are subjected to abrasion by grit-blasting to remove a thin layer from the upper surfaces thereby facilitating the subsequent application thereto of a surface coating. The coated tiles are conveyed to a packaging station 14.