Fresh and rheological properties of 3D printing bio-cementbased materials

Abstract

The aim of this study is to investigate the effect of different mix composition on fresh and rheological properties of a bio-printable mortar. Different binders were tested such as fly ash (FA), silica fume (SF), and used with CEMI and sand for a water/binder ratio of 0.50. Then, superplasticizer (SP) and natural flax fibres 15 mm (FL) were used in the investigation at varying percentage for a given binder. Two viscosity modifying agents were also tested. Adding flax fibres (0.2% to 0.6%) led to a greater yield stress, higher cohesiveness of the mix. It also demonstrated more stable structure of layers which allowed to not collapse under layer own weight and other successive layers. With the incorporation of fibres the time gap is reduced. Furthermore, positive effect of fibres can be reversed when the dosage in fibres is too high (difficulties to extrude and drainage phenomenon which led to a stiffening of the mix). VMA caused an important loss of workability and time gap which influenced the passing ability of the mix through the extruder. Increase SP led to an increase in slump flow and penetration values which can affect the stability of the shape of printed layers. Good linear correlation between slump flow and penetrometer was established.