3D printing geopolymer is a new type of building way and material with both of resource utilization and intelligent building. The mechanical properties in all directions and the bonding strength between layers of components are important factors affecting the constructability and durability of buildings.3D printing geopolymer mortar was prepared with fly ash and quartz sand as main raw materials, anhydrous sodium silicate as alkali activator, slag powder as auxiliary cementitious material, magnesium aluminum silicate as special additive. The 3D printing component of fly ash-based geopolymer was prepared under the condition of the optimum dosage and proportion. The interlayer bonding strength and tensile strength were studied, and the mechanical anisotropy properties were characterized by mechanical properties and ultrasonic pulse velocity.

The effect of cracking ages (i.e., 3, 7, 14 d and 28 d) on the self‒healing of pure fly ash-based engineered geopolymer composite (FA-EGC) was evaluated by crack characteristics, tensile properties and water absorption. The components and microstructure of self‒healing products of FA-EGC were investigated by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy with energy dispersive spectroscopy. The results show that there is an optimum self‒healing effect of FA-EGC samples when cracking age is 7 d, a better recovery of ultimate tensile strength and a reduction in average water absorption rate can be obtained at the maximum decrease in crack width. The self‒healing products of FA-EGC are the geopolymer gel generated by ongoing geopolymerization reaction and CaCO₃.