Abstract
Extrusion experiments were carried out with mortars of which fine aggregates had different geometries but a same particle size distribution. The mortars were prepared to various water contents, and extruded at several rotational speeds of screw. Both extruding pressure and velocity were measured. Graphic analyzer was used to measure fine aggregate geometries which correlated well with extrusion characteristics. That is, the more spherical the configuration of fine aggregate was, the lower the extruding pressure was, but the higher the velocity was. At comparatively low water content ratios, influences of fine aggregate geometry on the extruding velocity were a little, but much on the pressure. At the higher water content ratios, the effects could not be observed so obviously. Extruding pressure and velocity have been generally thought to be prescribed by the extruder operating point which is determined by a cross point of screw characteristics and die characteristics. This concept may be also applied to the mortars with various fine aggregate geometries. And the die characteristics of screw extrusion were found to be similar to those of piston extrusion. The extruding pressure was directly proportional to the shearing stress of mortar, but the extruding velocity was inversely. It is suggested that the shearing stress of mortar is used for a substitute of Y and τ_<R0> in Eq. 1 presented by Benbow.
