Thermal and Mechanical Properties of 3D Printed Lightweight Hollow Glass Microsphere Aggregate Concrete (2026-04)¶

To overcome the key bottleneck that 3D-Printed Lightweight Aggregate Concrete (3DPLAC) cannot simultaneously achieve adequate printability, mechanical strength, and thermal insulation, this study systematically evaluates the overall performance of 3D-Printed Hollow Glass Microsphere aggregate Concrete (3DP-HGMC). Cast Hollow Glass Microsphere aggregate Concrete (C-HGMC) was used as the control, and the volumetric replacement of sand with Hollow Glass Microspheres (HGM) was varied from 0% to 100%. A comprehensive experimental program was conducted to assess fresh-state workability, printability, thermal conductivity, and anisotropic mechanical properties. In addition, a hybrid multi-index evaluation method was used to identify the optimal HGM content. The results indicate that workability first improves and then deteriorates as the HGM dosage increases, owing to the competing ball-bearing effect and water-absorption behavior of HGM. Increasing HGM markedly reduces both thermal conductivity and apparent density. At 100% replacement, the thermal conductivity of C-HGMC decreases by 70% relative to normal concrete, and the 28-day compressive strength remains 47.82 MPa; however, this mixture is not printable. An HGM replacement of 50% is identified as optimal for 3DP-HGMC, which exhibits the best printability, achieves a 43% lower thermal conductivity than normal 3D-Printed Concrete (3DPC), and attains 28-day compressive strengths of at least 55 MPa in the X, Y, and Z directions. Overall, the optimal mix provides the best balance among printability, thermal insulation, and mechanical properties. These findings provide reference guidelines for developing low-carbon, energy-efficient 3DPC materials.