• Schutter, Geert De
• Yuan, Yong
• Rahul, A. V.
• Mohan, Manu K.
• Van Tittelboom, Kim
• Tao, Yaxin

Abstract

To achieve stiffening control in 3D concrete printing, a twin-pipe pumping (TPP) system has been developed,where two streams of cementitious materials are pumped separately via two pumps and blended over a helicalstatic mixer right before extrusion. However, in addition to the interlayer region, the presence of striationsconsisting of unmixed limestone-based regions reduces the mechanical integrity of printed elements in earlierresearch on TPP strategy making use of a cement-based mixture and a limestone-based mixture. In this work, weexamined the use of redispersible polymer powder (RDP) as a means to improve the mechanical performance ofsuch 3D printed elements. Limestone powder in the limestone-based mixture was partially substituted bydifferent dosages of redispersible polymer powder (5, 10, and 15 %). Rheological behavior of the cement-basedmixture and the limestone-based mixture was evaluated. Further, we studied the effect of RDP addition on thehydration and the early age mechanical behavior of the combined mixtures. In the hardened state, specimensextracted from 3D printed wall elements were tested for flexural, compressive, and tensile strength. Its microstructure was examined using scanning electron microscopy. From the results of various studies conducted,although adding redispersible polymer powder would slightly reduce the very early age mechanical strength, itenhances the mechanical integrity in the hardened state due to film formation in the limestone-based mixture.

Topics

• microstructure
• polymer
• scanning electron microscopy
• extrusion
• strength
• cement
• tensile strength