Analysis of Rheological Properties and Printability of a 3D Printing Mortar Containing Silica-Fume, Hydrated Lime, and Blast-Furnace-Slag (2023-09)¶

The changes in rheological properties based on mix design selection are critical factors in determining the success of a 3D-printed structure using cement-based materials. The inclusion of supplementary cementitious materials (SCMs) can significantly affect the rheology of 3D printing mixes. This research was conducted to analyse the synergic effects of different SCMs i.e., silica fume, blast furnace slag (BFS), and hydrated lime on the rheological behaviour and printability of a cementitious mortar for the first time. The results showed that replacing Portland cement with 6 wt.% silica fume and 6 wt.% lime increased the initial yield stress to about 24 times higher than the control. Also, the addition of lime in mixes containing silica fume increases the cohesiveness of the mix as time passed enhancing the printability of mixes. The outcomes indicated that the inclusion of silica fume and lime increased flocculation rate and thixotropy making the mixture easier to pump and extrude through the printer's nozzle in addition to increased buildability of the printed layers. Moreover, replacing Portland cement with up to 20 wt.% BFS has minor changes on the rheological properties and printability of mixes which allows using less cement in 3D-printing mixes to lower its embodied carbon footprint.