Biography

Dengwu Jiao is an Assistant Professor in the Department of Architecture and Civil Engineering at CityUHK. His research interest includes rheology control, sustainable concrete design, and 3D concrete printing. Currently, Prof. Jiao leads several projects from NSFC, RGC, ITC, ECF, Guangdong and Shenzhen Governments. Prof. Jiao has published more than 100 journal and conference papers, with over 80 papers indexed by SCI/EI. The Google Scholar citations is over 3700 with H-index of 28. Prof. Jiao has been recognized with RILEM Gustavo Colonnetti medal, ACF Distinguished Young Researcher Award, and IAAM Young Scientist Award. Prof. Jiao serves as the Fellow of HKCI, an editor of Applied Rheology and Scientific Reports, and Youth Editorial Board Member of several international journals.

Abstract

3D printing of concrete needs to meet the contradicting requirements regarding pumpability, extrudability, and buildability. On the one hand, the material needs to flow easily to be pumped towards the printing unit and to be extruded through the nozzle. On the other hand, after the printed material reaches its final position in the printed layers, the yield stress of the mixture should be high enough to maintain its shape under its own weight and the load from upper layers. Applying interventions at the print head to rapidly increase the buildability does not affect the pumpability of the concrete mix before extrusion. Active-rheology control, by means of pre-adding responsive additives and applying a magnetic field signal, is a promising method to overcome the contradicting rheological requirements in 3D printing cementitious materials. This presentation demonstrates a proof-of-concept system for enhancing the buildability and interlayer bonding of 3D printed steel fiber-reinforced concrete by applying magnetic stimuli after filament deposition. The results indicate that the cumulative height of the bottom layers directly above the magnetic field increased by 6.9% compared to unmagnetized regions, and the interlayer bonding strength increased by 31.1%, mainly attributed to the bridging effect of magneto-aligned fibers crossing the interfaces. This study validates the feasibility of applying magnetic intervention in assisting 3D concrete printing.