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3D printing technology has attracted great attention from the construction industry for its superior performance compared with traditional construction technology. In this study, the rheological properties of fresh mixed pastes with different contents of fly ash (FA) and granular ground blast furnace slag (GGBFS) were evaluated by analyzing rheology indices and the fitting of the Bingham model, and the relationship between the rheological properties, the buildability of 3D Printing Material (3DPM) and n value of the Rosin–Rammler distribution function was established. The results show that with increasing FA or GGBFS content, the rheological properties (fluidity, yield stress, and plastic viscosity) of fresh mixed pastes first improved and then deteriorated, and the n value (constant for the width of the particle distribution) first decreased and then increased. When the FA content was 20%, the paste fluidity reached a maximum value of 178 mm, the n value (1.01782) was the smallest, the particle size distribution was the widest, the accumulation was the best, and the buildability of 3DPM was the best. In addition, it can be seen from the SEM analysis that FA and GGBFS participate in the cement hydration to a limited extent, which mainly play the role of compaction and adjustment of particle size distribution. This is consistent with the test results of XRD. In short, by adjusting the amount of FA and GGBFS, the particle size distribution of the whole cementitious material system changes. When the fluidity of 3DPM was between 160 and 180 mm, the smaller the n value of the Rosin–Rammler distribution function, the better its buildability was. [ABSTRACT FROM AUTHOR]

• The FA-GGBFS employed into the mix of cement-based 3DPM(3D printing materials) and the compressive strength, rheology, and printing were explored. • The relationship slump and expansion-rheological-properties of 3DPM was studied. • The best formulation was due to the fly ash (FA) content working as a rheology regulator. Recent advances have proposed new requirements on the controlling of the compressive strength, the rheology, and the printing properties of cement-based 3D printing material. In this study, by modifying the pastes with inorganic regulators such as fly ash (FA) and Granular ground blast furnace slag (GGBFS), a 3D printing cement-based material with outstanding these behaviors was created. The results show that the slump and expansion of fresh pastes first increased and then decreased as the amount of FA/GGBFS replacing the cement increased. The setting time increased gradually with increasing FA content, up to 5.07 min after that of the cement without FA/GGBFS, and the flexural strength and compressive strength decreased gradually. This condition was beneficial to the extrusion of the mortar and caused the buildability to improve and then deteriorate. The extrusion fracture length ranged from 40 mm to 98 mm. Furthermore, when the FA content was 20%, the slump and expansion of the pastes reached their maximums, 42 mm and 185 mm, respectively. And the flexural strength and compressive strength of the mortar at 28 d were 10.6 MPa and 60.8 MPa, respectively. The apparent viscosity and shear stress are the smallest, and the extrusion and buildability are the best under these conditions. Finally, the house (length × width × height is 36×30×19 cm) and the roof (length × width × height is 38×32×3.0 cm) were printed according to the ratio of 1: 150. [ABSTRACT FROM AUTHOR]