Crack propagation and failure mechanism of 3D printing engineered cementitious composites (3DP-ECC) under bending loads

Abstract

Engineered cementitious composites (ECC), as a self-reinforcing material featuring the characteristic of multiple cracking and strain hardening, provides a feasible solution to overcome the dependence on steel reinforcement in 3D concrete printing (3DCP). Nevertheless, interlayers in 3D printing ECC (3DP-ECC) create potential paths for crack propagation under bending load, which is expected to result in different failure mechanisms for bent 3DP-ECC. Different from the conventional multiple cracking behaviors of cast ECC, the test results reveal that 3DP-ECC exhibits two new crack propagation modes depending on the interface bond strength. In the first mode, bending cracks deflect into the interlayer, leading to the splitting of two adjacent filaments, while the filaments in the upper part of the interface crack countinue to exhibit multiple cracking behavior and bear loads. In the second mode, the localized shearing cracks became dominant when the interlayer bond strength was excessively low. This study comprehensively discusses the bending performance and failure mechanisms of 3DP-ECC exhibiting different crack propagation modes. The findings are valuable for enhancing the ductility design of 3DP-ECC beam components, ultimately contributing to the improvement of 3D concrete printing technology.