Of the digital concrete-additive-manufacturing techniques, extrusion-based systems are probably the most widespread and studied. Despite the significant potential offered by 3D printing, several challenges must still be overcome. For instance, although several solutions have already been explored, the automated reinforcement of the layer-wise printed structures represents a challenge. The inline quality control of the fresh-state properties of 3D-printed materials is also an open question that needs to be addressed to find an efficient shared practice. This study proposes a new device designed to simultaneously reinforce 3D-printed structures along and through the layers and to be used as an inline quality-control device. This device consists in a sewing system, which is composed of a rotating system, and a hollow needle, which drives a reinforcing cable or yarn and can be used to inject cement grout to fill holes and improve bonding with reinforcement. The rotation is induced by a stepper motor, which measures the torque that is required to make the needle penetrate. This measurement can be used as a quality-control index to ensure material homogeneity. This paper aims to present an original reinforcement system that can be fully automated and simultaneously create reinforcement patterns in different directions of the printed structure while controlling the material's fresh properties.
Keywords: 3D concrete printing; in-line quality control; reinforcement; sewing device; yield stress.