Anisotropy and Mechanical Enhancement of 3D-Printed Vitrified Microsphere Thermal Insulation Mortar Incorporating Basalt Fiber Under Different Printing Paths (2026-01)¶

3D-printed vitrified microsphere thermal insulation mortar (3DP-VMIM) possesses excellent thermal insulation but insufficient strength and anisotropy control. This study explores the combined effects of basalt fiber (BF) incorporation and printing path on its anisotropic and mechanical behaviors. Mortars with five BF contents (0, 0.3 %, 0.6 %, 0.9 %, 1.2 %) are printed using parallel (Path-A) and cross (Path-B) interlayer paths, and tested for fluidity, shape retention, dry density, thermal conductivity, and strength, complemented by SEM analysis. As BF content increases, fluidity decreases while shape retention improves; shape retention exceeds 80 % after 60 min when BF ≥ 0.9 %. The dry density and thermal conductivity of 3DP-VMIM peak at 0.9 % BF. Due to the mechanical interlocking effect mitigating the adverse impact of interlayer weak planes, Path-B exhibits significantly superior mechanical performance and density compared to Path-A. Moreover, Path-A and Path-B exhibit optimal compressive strength in the X and Y directions, respectively, while their flexural strength peaks in the Y and Z directions, respectively. In Path-A, the X-direction is more affected by interstrip and interlayer weak planes, resulting in a thermal conductivity pattern of X > Y > Z. In Path-B, the Y-direction exhibits more pronounced weakening from interstrip interfaces, resulting in Y > X > Z. Moderate BF addition improves interfacial bonding, while excessive fiber causes agglomeration. Overall, the optimal BF content is 0.9 %. Although sacrifices some thermal insulation performance, it yields the best mechanical properties. Path-A demonstrates superior thermal insulation performance, while Path-B exhibits stronger mechanical properties and enhanced anisotropy stability.