Evaluation of cold joint effects on the microstructure and mechanical behavior of three‐dimensional printed concrete specimen

Abstract

3D concrete printing (3DCP) is an automated construction technique that uses an extrusion process to fabricate structures efficiently. However, the layer‐by‐layer process can create interlayer weaknesses, and interruptions during printing can result in cold joints, which can negatively affect the structural behavior. This study analyzed the characteristics of cold joints and their influence on 3DCP behavior. The microstructure was characterized by examining specimens with a 90 min interlayer interval. A splitting tensile test was conducted to evaluate the tensile strength of the bulk concrete and bond strength at the cold joint. This test identified correlations between microstructure and mechanical properties. Additionally, three‐point bending tests were performed on both reference (without cold joints) and cold joint specimens using single‐edge notched beam and eccentric single‐edge notched beam configurations to evaluate the influence of cold joints on crack propagation and flexural strength. The results revealed that cold joints exhibited significantly higher porosities and poorer mechanical properties. Cold joints also affected crack patterns, thus changing the overall structural behavior of 3DCP. This study improved understanding of the structural performance of 3DCP with cold joints.