Effect of metakaolin and natural fibres on three-dimensional printing mortar

Abstract

The aim of this study was to investigate the effect of different parameters of the mix composition on the fresh and rheological properties of printable mortar. Metakaolin, limestone filler and fly ash were tested as binders. The water/binder ratio was set as 0.50. Superplasticiser (SP), viscosity-modifying admixture (VMA, nanoclay based) and natural sisal fibres were used at different percentages. The positive effect of fibres was reversed when the dosage of fibres was too high (difficulties in extruding and drainage phenomenon, which led to a stiffening of the mix). The VMA caused an important loss of workability and time gap, which influenced the passing ability of the mix through the extruder. Adding sisal fibres led to a greater yield stress and higher cohesiveness of the mix. Increased SP dosage led to an increase in slump flow and penetration values and reduced the yield stress, which affected the stability of the shape of printed layers.