Abstract: Successive coating a lay of postponed-set mortar (PSM) on prestressed strand is a key to engineering application for a new type of bond-retarded prestressed concrete system. According to the principle of screw conveying and die forming, coating equipment for bond-retarded prestressed strand is developed and coating experiments are carried out. Based on the theories of rheology, successive coating process of PSM is analyzed. The theoretical analysis and the experimental results show the followings. In order to achieve automatically and successively coating PSM and plastic (sealing PSM) on prestressed strand only once, both PSM with Bingham plastic in screw channel and annular passage surrounding strand and polyethylene sheath must be in fully flow state, which means screw revolutions and coating velocity exist respective critical values.

Key words: Postponed-set mortar, Prestressed concrete strand, Successive coating