The Contribution of 3D Printed Lost Formworks to the Compressive Capacity of Structural Columns (2024-11)¶

Large-scale cement-based Additive Manufacturing (AM), also known as 3D Concrete Printing (3DCP), is a promising technique aimed at innovating the construction industry. Although proto-type 3DCP homes have been built around the world, the structural performance of large-scale printed elements is not fully understood yet. 3D-printed structures, in particular columns, have already been utilised as lost formworks. However, there is a significant lack of knowledge regarding the structural contribution as well as the confining effect of printed formwork. The goal of this research is to investigate experimentally the behaviour under pure compression of columns with 3D printed shells. Limestone-calcined-clay-cement (LC3)-based mortar is used for the printed shell. A concrete mix is utilised for the inner core of the specimens. Traditional cast concrete columns are also tested (using the same concrete mix) and used as a benchmark. A total of 9 specimens are tested at the age of 28 days, 3 cast columns, 3 printed columns and 3 printed columns with extra interlayer stirrups (placed every 5 layers). Traditional reinforcement is used in all cases. The printed filament width of the shell is 27±2 mm, and a concrete cover of 30 mm is selected for all the specimens. Due to the lack of guidance on dimensioning and detailing the 3DCP elements, columns have been designed according to the Seismic Design Guide for Low-rise Confined Masonry (CM) buildings. The interlayer stirrups are proposed as an economical solution to enhance the confinement effect of the printed shells. Therefore, the early spalling of the printed shells mentioned in the literature may be delayed and the shell could contribute to the load-bearing capacity of the column. This paper presents the experimental research plan for testing 3D printed columns.