- Title
- Development of structural-functional integrated concrete
- Creator
- Mohseni, Ehsan
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2021
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The present research goals are to clarify how phase change material (PCM)-composite materials can be leveraged for energy consumption reduction in buildings and also to provide cost savings to ratepayers. PCMs are able to storing thermal energy in the form of latent heat when exposed to temperatures exceeding their melting point by undergoing a phase transition from a solid to liquid state. In addition, PCMs also have the capability to release this thermal energy when the system temperature decreases below their solidification point. The aim of implementing composite PCM building elements such as walls is to substantially decrease and time-shift the maximum thermal load on the building in order to subtract and smooth out the electricity demand for heating and cooling. Based on the previous studies, concrete with encapsulated PCM is usually limited to non-structural applications due to its low strength properties, and the interfacial transition zone (ITZ) between hardened cement paste and LWA has been known as an area of weakness in lightweight concrete, both in terms of strength and the permeation of fluids. In addition, inorganic PCMs as a cheap material are corrosive to most metals. To extend the use of PCM-composite for both structural and functional applications, an analysis with a consideration of the hydration products and microstructure of cement-based materials in the presence of PCM is essential in understanding the behaviour of PCM-concrete and the reasons behind the changes in mechanical and durability properties and thermal performance. The effectiveness of various PCMs has not yet been quantitatively assessed to identify which are superior. In this study, different types of PCMs based on their thermal performance and economic efficiency with focus on industry viability were evaluated and ranked. Moreover, an economic and environmental case study evaluation was undertaken in a typical New South Wales home, in order to investigate the viability of PCM-concrete as a thermally efficient building material and to choose for experimental part. The practical ranking system indicated the capability of PCM-concrete in improvement of the construction material, and this technology could help Australia reach its 2030 GHG emissions reduction target, if subsequent research suggests it can be safely implemented in the near future. An inorganic PCM with high overall ranking was selected from this evaluation to be studied experimentally in the laboratory. Besides, an organic PCM from the market with an appropriate performance was selected for comparison. In the experimental part, a structural lightweight concrete that has the function of indoor temperature control was developed by using thermal energy storage aggregate (TESA). TESA is made of a porous structural lightweight aggregate impregnated with liquid PCM and is coated with epoxy resins and mineral admixtures. In order to develop TESA, experimental investigations were undertaken by way of substituting coarse aggregates with varying amounts of PCM composite. A macro-encapsulated technique that uses vacuum impregnation was applied for the incorporation of two types of PCMs (organic and inorganic) into porous aggregate, namely scoria, as a container for PCMs. The structural and functional performances of TESA concrete were then investigated through microstructure, thermal, mechanical and durability studies and analyses. The techniques employed in this study indicated that the incorporation of PCM in the TESA system does not result in significant strength loss and TESA had the ability to mitigate the negative effect of thermal cycling and contributed to reducing thermal cracks. The 28-day compressive strength of TESA concretes ranged from 28.12 MPa to 40.0 MPa, which is considered suitable for structural concrete applications in accordance with the Australian Standard. The improvement of durability and reduction of probability of corrosion of concrete containing TESA can be ascribed to the dual-layer coating system, which covered the surface of LWA appropriately. Thermal performance graphs proved that TESA composites were able to decrease the peak indoor temperature by absorbing heat. They were also effective in transferring the heating and cooling loads from peak demand times. Furthermore, to mitigate the poor heat transfer of PCM-concrete, the influence of nano titanium (NT) as a high conductive material on mechanical properties, thermal performance, thermal conductivity and corrosion was studied. The addition of 5wt.% NT to the mixtures increased the compressive strength by about 25%, and reduced the corrosion possibility significantly. NT improved the thermal conductivity of samples with PCM, and the speed of the charging and discharging of TESA was increased by using NT beside the PCM. The relationships between numerical approaches and experimental data were investigated to provide more flexibility in terms of analysing the influence of various parameters and, hence, choosing the optimum solution for PCM applications in buildings. PCMs with different melting temperatures and thicknesses placed in different positions was applied in buildings simulated by EnergyPlus software. The results reported that, in summer, the model containing PCM positioned in the roof-wall with a thickness of 10 mm and a melting temperature of 25℃ had the maximum decrease in energy consumption. However, the best performance in winter energy consumption was demonstrated in the model containing PCM with a melting temperature of 21℃; hence, the optimal melting temperature was found to be seasonal. The energy saving by the application of PCM with a suitable melting temperature was due to the absorption of excessive heat and reducing the need for more energy for indoor cooling. It was found that the application of PCM with 10 mm thickness decreases the amount of CO2 emitted by oil, natural gas and coal. Therefore, it can be reported that the use of PCM in the buildings is environmentally useful. To wrap up, the novel TESA-concrete developed in this study can be successfully integrated into the structural concrete to serve both structural and thermal functions, and using PCM can contribute to the sustainability of construction industry.
- Subject
- phase change materials; marco-encapsulated method; thermal efficiency; thermal energy storage aggregate; energy analysis
- Identifier
- http://hdl.handle.net/1959.13/1422688
- Identifier
- uon:37866
- Rights
- Copyright 2021 Ehsan Mohseni
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 17 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 251 KB | Adobe Acrobat PDF | View Details Download |