Doctoral Degrees (Civil Engineering)

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Browsing Doctoral Degrees (Civil Engineering) by Subject "Aggregate industry"

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    Phase Change Material and Recycled Brick Aggregate in Thermal Energy Storage 3D Printed Concrete
    (Stellenbosch : Stellenbosch University, 2022-12) Christen, Heidi; Van Zijl, Gideon P. A. G.; De Villiers, Wibke; Stellenbosch University. Faculty of Engineering. Department of Civil Engineering.
    ENGLISH ABSTRACT: The building sector accounts for the highest share of anthropogenic greenhouse gas emissions from electricity and heat production, mostly due to the high energy requirement of heating, ventilation, and air conditioning systems in buildings. Passive design solutions are gaining popularity as a means to reduce the energy requirement of buildings while still providing thermal comfort in buildings. 3D printed concrete represents the next phase of automation in the construction industry with potential to allow for more complex structural geometries, with higher labour productivity, lower energy requirements, reduced waste, and a positive resulting impact on the environment. This research combines a thermal energy storage passive design solution in the form of phase change material, with 3D printed concrete, using recycled brick aggregate as a vessel for the phase change material in the concrete. This research therefore analyses a novel material with aspects of energy saving, automation and recycling. This research is original in its characterisation of a 3D printable concrete containing recycled brick aggregate, and its investigation of leakage of phase change material from recycled brick aggregate in 3D printed concrete. Two mix designs are developed, the first replacing a large portion of the natural aggregate in a 3D printed concrete mix with recycled brick aggregate, and the second adding phase change material to the pores of the recycled brick aggregate to create phase change material 3D printed concrete. Rheological and mechanical characterisations are performed on both developed mixes and compared to a reference 3D printed concrete mix. Mass-loss tests, scanning electron microscopy analysis and 90-day strength tests are used to analyse the internal and external phase change material leakage. Two façade sections are printed with the two mix designs and used in thermal tests to analyse the effectiveness of the chosen phase change material in the façade geometry during different months of early spring to late summer in Stellenbosch, South Africa. The effectiveness of the phase change material after several months of exposure to outdoor ambient conditions proved a successful vacuum impregnation technique of phase change material in recycled brick aggregate. A model of the phase change material 3D printed façade section was created in ABAQUS and validated by the experimental thermal tests, with the material thermal properties being determined by a sensitivity study. The validated model was used to determine two phase change material melting temperatures which could potentially be incorporated into the façade section for saving both cooling and heating energy in summer and winter respectively, due to their activation at separate temperature ranges.