Extrusion of cement‐based materials ‐ an overview

Abstract

Extrusion is a process which consists in forcing a formable material to pass through a die having the cross‐section of the part to be obtained. This way of processing is used with both conventional and fibre‐reinforced cement‐based materials to fabricate various construction elements such as panels, pipes, and roadside kerbs. Recently, with the development of digital fabrication methods and, especially, 3D concrete printing by selective deposition, extrusion techniques have aroused a significant increase in interest. This study describes screw and ram extrusion techniques and their applications in the construction industry. Furthermore, the underlying mechanisms which are part of extrusion flow are delineated, and the roles of rheological and hydro‐mechanical behaviour, the latter in a context of soil mechanics, in defining the extrudability of the cementitious materials are highlighted. Finally, specific points such as flow‐induced anisotropy of fibre‐reinforced cementitious materials or surface defects are addressed.