Effect of activator dosage and mass ratio of GGBFS to FA on 3D printing performance of kenaf geopolymer

Kenaf geopolymer for 3D printing is a promising representative for comprehensive and intelligent utilization of industrial and agricultural wastes. Aiming at exploring the effect of raw materials’ proportion on printing performances, alkali activator dosage (10 wt.%, 15 wt.%, 20 wt.%) and mass ratio of ground granulated blast furnace slag (GGBFS) to fly ash (FA) (15:85, 20:80, 25:75) were adopted as main variables in this paper. Results have shown that increasing the activator dosage and decreasing the mass ratio of GGBFS to FA can improve the flowability, and adjusting these two parameters can tailor the fluidity to a suitable range. Moreover, dry density of kenaf geopolymer was more significantly affected by alkali activator dosage compared with mineral powder ratio, and lightweight characteristic due to kenaf participation effectively improved shape retention ability of printed specimens. Besides, microstructure analysis further confirmed that with appropriate alkali activator dosage and mineral powder ratio, high level of geopolymerization reaction can be achieved to produce enough gel product for a satisfactory internal structure, which externally manifested as excellent printability and mechanical strength. Finally, formula with alkali activator dosage of 15 wt.% and GGBFS to FA mass ratio of 25:75 was recommended for satisfactory printing performance and mechanical properties.