Self-forming curved moulds

This thesis introduces a novel low-tech adaptable casting technique for production of double-curved non-uniform concrete panels. Presently, there are numerous studies into creating formwork for casting concrete in complex shapes and the techniques are ever evolving. However, flexible formwork has yet to find widespread industrial application. This thesis gives an overview of the current state of the art, looking briefly at traditional formwork, such as wooden and steel formworks, but focuses mainly on novel concrete casting techniques, such as Fabric formwork, 3D-printing, adaptable moulds, as well as subtractive formwork such as, CNC-milling and hotwire cutting. 

Similar to the above-mentioned techniques, this thesis presents a concrete casting method using foam formwork, namely extruded polystyrene (XPS). The research explores how XPS becomes malleable when submerged in a solution of acetone and water. The XPS maintains deformation upon drying. This simple, low-tech approach makes it more accessible and, compared to CNC-Milling, it requires less material. 

The research includes qualitative experimentation of 3 parameters. Firstly, the effects of different concentrations of acetone solutions on XPS. Secondly, variable thicknesses of XPS samples, and lastly, duration of the submersion of XPS samples into acetone-water solutions.

The research continues with the development of a fabrication process, which introduces a gravity-informed self-forming XPS mould. The method incorporates a geometric pattern within the extruded polystyrene, which controls the shape of the mould surface and subsequently the shape of the concrete results. This technique is tested and adjusted through a series of experiments, which conclude with a case study, presenting a possible application of the method. In the case study, 9 concrete façade tiles are fabricated. 

From the research it is concluded that this technique is viable for the production of double-curved, non-uniform concrete elements.