Compressive behavior of 3D printed concrete with different printing paths and concrete ages

As an intelligent construction technology, 3D printed concrete has made great progress in recent years, but research on the development law of hardened mechanical properties of 3D printed concrete is relatively limited, and the influence of printing path on compressive behavior of 3D printed concrete still needs further research. This paper proposed a new printing path for extrusion based 3D printed concrete and investigated the compressive behavior of hardened concrete printed by the new printing path. The effect of printing path, concrete age, printing speed, specimen size, and replacement of natural sand by recycled sand were evaluated through compressive tests of specimens printed by different path at different ages. Compared with the traditional printing path, the new printing path could increase peak strain, elastic modulus, and cubic compressive strength of the printed concrete. The new printing path provided a preferable alternative solution for printed concrete subjected to compression. The results also indicate that the compressive strength of printed concrete at 3 days can reach 45%-62% of the 28-day compressive strength, and the compressive strength at 7 days appears to achieve 68%-89% of the 28-day compressive strength, and the printing path has minor effect on the development rate of compressive strength. Based on the test data analyses, an analytical model was proposed to describe the stress-strain relationship of concrete printed by two printing paths.