Abstract
Extrusion experiments were carried out on mortars to which some gelled substances were added to reduce friction between the materials in the mortars. Both extruding pressure and velocity were measured to elucidate the extrusion characteristics of mortars. The mortars were prepared under several conditions by changing water content, rotational frequency of screw, amount of gelled substance and gelation time.
When the amount of gelled substance added was kept constant in the mortars, the extrusion pressure decreased and the extrusion velocity increased with increasing water content. The same behavior was observed when the amount of gelled substance was decreased, contrary to expectation. In the present study, no effect was observed for the extrusion characteristics of mortars when gelled substance was added. It seems that the gelled substance works only as a porous aggregate.
Extruding pressure and velocity have been generally known 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 applied to the present mortar-gelled substance system. The die characteristics of screw extrusion were found to be similar to those of piston extrusion.
