Printability and interlayer bonding property of 3D printed fiber reinforced geopolymer (3DP-FRG)

The interlayer bonding property is crucial for 3D printed fiber reinforced geopolymer (3DP-FRG). The effects of fiber content and interval time on printability and interlayer bonding property of 3DP-FRG were studied, including printability, stability, mechanical property, interlayer drying shrinkage, interlayer relative humidity, average interlayer gap width, and interlayer self-healing products. The results showed that fiber has both advantages and disadvantages for 3DP-FRG. The fiber improves stability, mechanical properties, and drying shrinkage properties of 3DP-FRG and has the optimum fiber content of 0.5 vol%. However, fiber negatively affects printability, interlayer relative humidity, and average interlayer gap width. When the interval time is less than 20 min, the interval time has no significant effect on the interlayer bonding property. The 28 d compressive strength, flexural strength, and interlayer bonding strength of 3DP-FRG with 0.5 vol% fiber increases by 24%, 14%, and 9% compared with the blank specimen, the 28 d drying shrinkage reduced by 27%, and the 28 d average interlayer gap width increases from 27 μm to 42 μm, respectively. 3DP-FRG has a certain potential for interlayer gaps self-healing; the self-healing products are N(C)-A-S-H gel, calcite, and sodium zeolite. The self-healing products, unreacted fly ash, and sand fill the interlayer gap. Moreover, fibers wrapped by a self-healing product can pass through the interlayer gap to connect adjacent layers.