Acoustic emission examination of 3D printed ultra-high performance concrete with and without coarse aggregate under fresh and hardened states

In this study, plain and fibered 3D printable ultra-high performance concrete mixes with and without coarse aggregate are characterized in the fresh and hardened state using acoustic emission testing. In the fresh state, the flow table, slump value, and open time tests are conducted, and acoustic emission parameters are used to determine the transition of the concrete from a printable phase to a non-printable phase. In the hardened state, the influence of rise time to amplitude ratio, and average frequency in the X, Y, and Z directions is analysed to characterize AE responses in compression, split, flexure, and fracture. The fracture behavior is evaluated using specimens with notch-to-depth ratios of 0.05, 0.2, and 0.5, where fracture energy and AE energy are interlinked to understand failure mechanisms. From the test results, it was found that acoustic emission tests characterize the anisotropic behavior in 3D printed specimens and determine the printability states. • Characterization of four types of 3D-printable ultra high performance concrete mixes using Acoustic Emission (AE) testing. • Printable and non-printable states are identified in fresh concrete condition. • In hardened state compression, tension, flexure and fracture test conducted. • AE parameters are sensitive to testing direction (X, Y, Z) and testing mode. • AE testing could identify anisotropic properties.