Explosion resistance of 3D printing ultra-high performance concrete based on contact explosion tests

In spite of anisotropy and layer interface weakness intrinsic to the 3D printing procedure, 3D printed ultra-high performance concrete (3DP-UHPC) exhibits excellent mechanical performance due to fiber alignment. For the first time, 3DP-UHPC slab, 3DP-UHPC reinforced normal concrete (PURN) slabs are tested against contact explosions. Explosion resistances with regard to different reinforcing methods, layer thickness ratios and construction methods for base materials are investigated. Specifically, PURN, steel bar reinforced 3DP-UHPC (RU), steel bar reinforced normal concrete (RC), and normal concrete (NC) slabs of similar sizes are constructed to compare the explosion resistances. Different reinforcing layer thickness are attempted. From the contact explosion tests, it exhibits that the extrusion-based 3D printing procedure enhances the explosion resistance substantially via fiber orientation alignment. With the layer thickness ratio of 40% (PURN6) as the watershed, both the top and bottom surface crater diameters of PURN slabs increase first and then decrease with increasing reinforcing layer thickness. In particular, crater diameters and failure modes for PURN8 and PURN15 are consistent with those of RC and RU, respectively. The underlying mechanism for the fibers to be aligned by the 3D printing procedure is theoretically analyzed to support the conclusions. The material costs of all the slabs are compared. The costs of PURN8 and PURN15 are 1.7 and 0.8 times of those for RC and RU, respectively. Thus, it can be stated that the 3D extrusion-based printing procedure will avail explosion resistance for 3DP-UHPC. Current test results prove the feasibility and cost-effectiveness of PURN for protective structures.