Evaluation of the Performance of Reinforced Concrete Beams with 3D-Printed Permanent Formwork
Jingyuan Guan, Li Wang, Yimiao Huang, Guowei Ma, Yaxin Tao
Abstract
Comprehension of the advantages of combining traditional construction method and 3D concrete printing is the gateway to general structural applicability of 3D concrete printing technology. To this objective, in this study, 3D-printed concrete is used as permanent formwork to manufacture reinforced concrete beams. Different treatment methods for interfaces between printed formwork and the cast core concrete, including embedding of shear connectors and entraining of micro cables, and deploying ribs in the 3D printing process of formwork, are explored to improve the integrated mechanical capacities of the so-called 3D printing and cast-in-place composite beams. Specifically, the flexural behaviours are studied experimentally through observation of damage and failure processes via visualisation with the digital image correlation (DIC) method. The mesoscale architecture at interface between 3D-printed permanent formwork and cast-in-place concrete is probed through CT scanning to infer the cooperative bonding mechanisms with regard to different bonding treatment methods. The stress-transfer mechanism is thus elucidated. The applicability of 3D-printed concrete as permanent formwork is validated in view of that 14.3% increase in bending capacity from the composite beam with bottom ribs compared to that of the completely cast counterpart. From the experiments, incorporation of shear connectors contributes most to the bonding performance of the formwork-concrete interfaces. Meanwhile, the interfacial bonding can be enhanced by increasing the roughness of the 3D printed formwork, interlocking with inner aggregated concrete or improving consistency in elastic and shear moduli of formwork and cast concrete. Particularly, the appropriate thickness of both the formwork and aggregated concrete as the cover to yield optimal integrated bending capacity of composite beams are derived from the current study.