Fabrication of Functionally Graded-cellular Structures of Cement-based Materials by Co- extrusion

Co-extrasion involves extrasion of multiple layers at the same time. Functionally graded materials comprising various layers with different properties can be produced through co-extrusion. Rheological control is vital for successful co-extrusion of layered cement-based materials. The paste flow in the barrel and the die land in a ram extruder should be plug-like, while the paste should be sheared and uniformly elongated in the die entry region. In this work, the rheology of the layered pastes was adjusted by changing the water content in each layer. An economical method using thinwall tubes was effective to prepare layered feedrod of cementitious paste. The functionally graded cellular structures of cement-based materials were successfully fabricated by co-extrusion at a low extrudate velocity. Inspections showed that the roundness perpendicular to the extrusion direction, and the straightness parallel to the extrusion direction between layers were well preserved after extrusion. The transition between layers was gradual, which is critical for functionally graded materials.