Effect of FA and GGBFS on compressive strength, rheology, and printing properties of cement-based 3D printing material

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 x width x height is 36x30x19 cm) and the roof (length x width x height is 38x32x3.0 cm) were printed according to the ratio of 1: 150.