This paper describes a method for the design and fabrication of complex funicular structures from discrete precast concrete elements. It has a critical look over conventional casting methods and proposes a parametric casting mold to produce concrete blocks with custom shapes. The research proposes that through the integration of digital form-finding techniques, computational file-to-fabrication workflows, and innovative sustainable casting techniques, complex funicular structures can be constructed using prefabricated elements in a practical, affordable, and materially efficient manner. / text

Many industrial processes generate large amounts of waste. Typical examples include the fertiliser industry (phosphogypsum), ferro-alloy and steel producers (slag), as well as the power generating industry (fly ash). Although some waste products are currently used to a limited extend (e.g. fly ash and cement in cement), there is a constant need to find more uses and newapplications for these. This investigation describes work done to develop a novel ceramic body, which can potentially be used as a ceramic filter for purification of waste water and potable water.

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Refractory materials must, in their everyday environment, withstand high stress levels which are a result of mechanical and thermal loadings. Any failure which results from these applied stresses can have serious financial and human consequences and therefore should be avoided. One key aspect to understanding the thermal shock behaviour of refractories is the mechanical behaviour at low temperatures. In this thesis the mechanical behaviour of a small range of multiphase refractories is explored. In particular the stress-strain response and its influence on the fracture behaviour is investigated. Experiments, performed on magnesia and magnesia spinel composites, indicate that non-linear stress-strain behaviour accompanied by permanent deformation upon unloading is a result of the release of microscale residual stresses by microcracking. A micromechanical constitutive model combining these features was developed using linear elastic composite theory and isotropic continuum damage mechanics. This non-linear stress-strain behaviour also gives rise to increasing toughness as crack propagation occurs. This increase in toughness results from an expansion which occurs when microscale residual stresses in front of the crack tip are relaxed by microcracking. A micromechanical model has been developed based upon the specifically developed constitutive model and previous work on transformation toughening. These models are capable not only of simulating experimental results, but can also indicate the microstructures which are most likely to exhibit extensive non-linear stress-strain behaviour and strongly rising toughness curves.

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The DC casting process used for the production of cast aluminium alloy products intended for processing by rolling, extrusion or forging is an economically important process with approximately 10 million tonnes of DC cast product being produced annually world wide [1]. Process productivity, particularly with respect to elimination of casting defects and hence process scrap is an important factor to DC cast product producers. The literature reporting the DC casting process, particularly with respect to the formation of defects on the cast surface, is reviewed and the mechanisms for the formation of such defects examined. A universally understood and accepted explanation was found for only one of the normal surface defects encountered in practice. A number of samples of commercially cast DC products were subject to detailed cast surface examination, particularly surface microstructures. The results of this examination and the literature survey identified molten metal surface tension as a possible contributing factor affecting the molten metal meniscus stability within the DC casting mould. Meniscus instability is linked with the formation of surface defects. The literature on surface tension of aluminium alloys provided only limited information hence the surface tension of a range of binary and ternary alloys, including commercial alloys was determined, producing data hitherto not available. Of the common alloying elements used in commercial aluminium alloys, iron and magnesium were found to significantly reduce the surface tension. Surface fracture also resulted in a reduction in surface tension for the majority of alloys tested. The surface tension data is combined with mould thermal and physical model calculations to propose a mechanism for the formation of the cast surface defects. The model proposes a maximum stable size for the meniscus according to the alloy and mould conditions. Conditions outside these limits result in meniscus instability and the formation of cast surface defects. The model suggests possible operating changes that may reduce the incidence of surface defect formation. The work also identifies a number of areas requiring further investigation before major practical process changes aimed at cast surface defect elimination, may be formulated.