Thesis
Biomineralised hydroxyapatite as a cement coating
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2018
- Thesis identifier
- T15135
- Person Identifier (Local)
- 201458527
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Ordinary Portland Cement (OPC) is the World’s most widely used building material. Cement is thus vulnerable to degradation through many processes. Bacteria are capable of generating minerals, in a process called biomineralisation. This may lead to the formation of many different minerals. There is precedent for applying biomineralisation processes to the repair and preservation of cements and concretes. In this thesis, we observe and describe for the first time the bacterially-mediated deposition of a hydroxyapatite coating onto OPC, and describe the biochemical mechanisms underlying this process. The biogenic hydroxyapatite deposition takes place in a synergistic process with the cement substrate material; utilising a Pseudomonas fluorescens biofilm, phosphates from the growth medium, and calcium from the cement substrate and pore solution. We additionally investigate the capacity of P. fluorescens to form biofilms under varied environmental conditions of temperature and carbon source availability, which is relevant to the application of the identified biogenic deposition system in the built environment. The investigation of P. fluorescens biofilms under these conditions is yet to be reported in the literature. We also establish that varied P. fluorescens morphologies may emerge under different environmental conditions, and carry out a novel structural characterisation and assay the fitness of these varied colony morphologies. Developing upon these initial investigations, we characterise this biogenic hydroxyapatite in detail using TEM, SEM-EDS, XRD, synchrotron-SAXS, and Mossbauer spectroscopy. We identify that this biogenic hydroxyapatite presents a less crystalline; plate like morphology, and reduced primary particle size in comparison to abiotic hydroxyapatite. The functional capacities of this biogenic hydroxyapatite as an OPC coating material are also investigated. We use focus-variation microscopy to characterise the surface topography of the coating, nanoindentation to measure the hardness and elastic modulus of the biogenic and abiotic hydroxyapatites, in combination with X-CT analysis to establish the completeness of the deposition process, and contact-angle measurements to investigate the hydrophobicity of the coating.
- Advisor / supervisor
- Hamilton, Andrea
- Renshaw, Joanna C.
- Resource Type
- Note
- Previously held under moratorium from 20th February 2019 until 20th February 2024.
- DOI
- Date Created
- 2018
- Former identifier
- 9912702293402996
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