Spray-Based 3D Printed Foam-Concrete (2024-08)¶

In this paper, based on the multiple effects of pore-filling, pore wall supporting, and low-density buffering, lightweight porous aggregate (i.e., expanded perlite-EP) is used to develop the spray-based 3D printed foam concrete with the dual performance of lightweight and high-strength for a tunnel-yielding support layer. The synergistic optimization mechanism of EP on the density and strength of printed foam concrete is systematically analyzed. The test results show that EP can effectively optimize the printability of foam concrete. It attributes that EP can greatly decrease the disturbing external forces on the foam during the spray-based 3D printing process, i.e., Fc, Fe, and Fz, and then improve the stability of the foam. Due to the low-density buffering effect, EP enhances the pore stability and optimizes the pore structure of printed foam concrete with the total porosity of S1-EP1 increased by 142.0 % to that of S1-EP0. Combined with the synergistic effect of density reduction and strength enhancement by EP, the spray-based 3D printed optimal lightweight and high-strength foam concrete (S2-EP1) achieves the maximum compressive strength of 16.9 MPa at 28 d with a density of 956 kg/m3. The S-3D printed S2-EP1 foam concrete layer increases the compressive strength of C30 concrete by 36.36 % under stress concentration loading conditions, which further demonstrates the effect of pressure-yielding support for tunnel lining structure.