An innovative formwork system based on ice and sand for casting optimised concrete components

Concrete is a principal construction material used worldwide. Formwork plays an important role in assisting geometry realisation and strength development of concrete elements. It is also one of the major costs in the construction of concrete structures. As energy consumption and carbon footprint have drawn many concerns in the construction industry, the material reduction of concrete structures becomes highly necessary. The drive towards efficient and eco-friendly civil construction has opened up great opportunities for applying optimisation techniques in the design of concrete structural components. Nevertheless, the geometries of optimised concrete components are often of complex shapes, which are difficult and costly to be cast using traditional formworks. Also, the existing flexible formwork systems e.g., CNC milling of Styrofoam and 3D printed plastic mould, usually have the problem of material waste. Considering the economic and ecological burden caused by material waste, a new formwork system which is flexible and recyclable with minimum construction cost becomes highly desirable. This thesis proposes a sustainable formwork system based on ice and sand for concrete casting, which is eco-friendly, recyclable and economical. In the proposed formwork system, ice is used as mould pattern to create desired geometry for concrete member, then sand mould is fabricated based on the ice pattern. A mix design and a mixing procedure for the proposed sand mould are developed, and compression tests are also performed to ensure the sufficient strength of the sand mould. Furthermore, surface preparation of the sand mould is investigated for easy demoulding and for achieving good concrete surface quality. To demonstrate the effectiveness of the new formwork system, customised 2D concrete components are fabricated. The finished components have smooth surfaces, and they match well with their designed shapes. Additionally, the recyclability of the proposed sand mould is tested. The results obtained from the mechanical tests indicate that the proposed sand mould can be fully recycled with satisfactory strength. The optimised 3D concrete structures are also successfully fabricated based on the mould with fully recycled sand. The new formwork system has demonstrated the possibility to be applied in construction industry towards a more sustainable and cleaner production of customised concrete components.