Foam and solvent: a low-tech self-forming casting technique for the production of double-curved asymmetrical concrete panels

Abstract

Considerable current research in the construction industry focuses on developing concrete elements in complex shapes. Traditional methods to achieve that are wooden or steel formworks, which are costly and constrained in shape. Novel methods such as fabric, 3D printed, and CNC milled formworks allow more formal possibilities. However, they come with design limitations, expensive infrastructure, and material waste. This paper introduces a novel low-tech and cost-efficient adaptable casting technique for the production of double-curved, asymmetrical concrete panels. The technique relies on extruded polystyrene foam (XPS), as a self-forming formwork. In particular, the research explores how XPS becomes malleable and stretchable when submerged in a solution of acetone and water. The formability of the XPS is controlled through three parameters: the concentration of the acetone solution, the thicknesses of XPS and the duration of the submersion. A case study of the production of 9 concrete panels with various thicknesses is presented in this paper. The weight of the cast concrete deforms the impregnated XPS formwork. This process allows the formation of both negative and positive curvature, which is controlled by the variable thickness of the formwork. In comparison to other adaptable formworks, the discussed low-tech technique is more accessible; while, in comparison to non-adaptable formworks, it reduces the material waste.