Bond-slip behaviour of textile-reinforcement in 3D printed concrete

Abstract

Integration of reinforcement in extrusion-based 3D concrete printing (3DCP) is one of the significant challenges that limit its structural application. Providing textile reinforcement having high tensile strength, easy formability and non-corrosive nature as a potential reinforcement for 3DCP members enhances their structural performance. However, the bond between the printed concrete and the textile reinforcement is an essential factor that affects the composite action. This study investigates the bond-slip behaviour of three types of textile reinforcements (i.e., AR-glass, basalt and carbon) in high-performance 3D printable concrete. The bond characteristics were evaluated using pull-out load test specimens. The effect of rheological properties like viscosity and yield strength on the bond behaviour was evaluated by varying the cement content with two different replacement dosages of fly ash and slag. The modification of the nozzle to incorporate textile reinforcement as an in-process reinforcement method for 3DCP is also discussed. Test results showed that the addition of fly ash reduced the viscosity and yield strength, thereby enhancing the bond strength and pull-out load. However, reduced viscosity and yield strength resulted in poor buildability. When compared to the control mix, the mix with 15% slag replacement showed 40% increased bond strength with good buildability and easy pumping. The modified nozzle incorporates the textile reinforcement during printing, and scanning electron microscopy images show that the printable concrete was observed to bond well with the multifilament yarns of the textile. Furthermore, analytical modelling was conducted to predict the pull-out load versus slip behaviour, and a comparison of the predicted and experimental behaviour is presented.