http://bura.brunel.ac.uk/handle/2438/180 Thu, 16 Apr 2026 01:20:43 GMT 2026-04-16T01:20:43Z http://bura.brunel.ac.uk/handle/2438/33131 Title: An assessment of the unintended consequences of structural coastal flood protection Authors: Breen, Morgan James Abstract: This thesis investigates the unintended socio-hydrological consequences of structural coastal flood protections (SCFPs) and assesses the implications for coastal flood risk management strategy in the UK. Climate change, and the continued urban development of flood exposed areas can exacerbate coastal flood risk, and thus flood risk management authorities often tend towards structural coastal flood protection measures to minimise losses. However, these structurally proactive measures can lead to infrastructural lock-ins, whereby the decrease in flood probability from the defence can lead to increased urban development and population, ultimately leading to higher losses due to an inundation event. This process has been referred to as the Safe Development Paradox (SDP), a cross-cutting science-practice-policy challenge that requires a systematic understanding in the context of increased uncertainty associated with climate change and the United Nations Sustainable Development Goals. However, literature of the phenomena is limited, compounded by a lack of consistent terminology, limited geographic distribution, and a skewed emphasis on fluvial flooding. Moreover, despite being an island nation, the UK, to date, has had very little research conducted into these unintended consequences of structural flood protection. This thesis developed and applied a methodology that captures these coupled human-flood processes, by integrating well-established methods from other spheres of flood risk assessment in a novel way to explore the currently poorly understood phenomena in coastal settings. The study contributes to addressing this knowledge gap based on insights from three contrasting UK case studies: Portsmouth, Weston-super-Mare, and Southport. Differential analysis of historic LiDAR Digital Surface Models (DSMs) was used to identify temporal changes in the urban landscape to create a DSM of Difference (DoD), representing elevation change between two locations over time. Geostatistical testing, specifically t-tests, were then used to infer statistical significance of changes in urban development. The results reveal a consistent pattern: following completion or improvement of large-scale SCFPs, there is subsequent, and statistically significant, increases in coastal population and urban development within/near flood-exposed areas in all case studies, contrary to the limited flood-exposed development in neighbouring settlements, with no comparable defences constructed, or upgraded, during the same period. On average, new urban development occurs approximately 2 years after the completion of coastal flood defence projects. These data were then inputted into a newly developed agent-based model (ABM) that simulates futures changes under different climate scenarios. The results demonstrate that each SCFP project led to an initial decrease in Affected Population (AfP) following implementation, confirming the intended immediate benefits of flood risk reduction. However, long-term projections revealed significant unintended consequences under the scenarios where SCFPs were exceeded by Extreme Coastal Water Levels (ECWLs). For Southport and Weston-super-Mare, the ABM output shows a dramatic increase in AfP once ECWL surpassed the SCFP crest height, affecting a larger population than those initially protected, primarily due to the increased population growth behind the defences and the larger flood extent. Portsmouth, however, exhibited a more limited increase in AfP, attributed to its high urban density and limited room for further development behind the defences. This highlights how pre-existing land-use and population density can act as brakes on the unintended consequences of SCFPs. The thesis concludes with a recommendation for future flood risk managers and policymakers to be aware of these unintended socio-hydrological consequences. SCFPs are crucial assets, and their construction and maintenance will continue to play an integral role in coastal adaptation to climate change, particularly in highly developed urban settlements. This thesis does not attempt to provide a comprehensive predictive modelling tool for planning, nor a detailed analysis of real estate markets, but instead focuses on socio-hydrological interactions of population change and SCFP. However, new SCFP design and implementation need to account for their long-term unintended consequences on communities and climate adaptation planning. In the short-term, flood risk communication provides a means of tackling these risks, improving flood memory, awareness, and preparedness. Furthermore, in the longer term a more holistic cost-benefit analysis and spatial planning strategy, internalising these factors should be utilised in order to create more sustainable and resilient coastal communities in the UK. Description: This thesis was submitted for the award of Master of Philosophy and was awarded by Brunel University London Thu, 01 Jan 2026 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/33131 2026-01-01T00:00:00Z http://bura.brunel.ac.uk/handle/2438/32798 Title: Effects and mechanisms of reactive nanoparticles and triethanolamine on the properties of limestone calcined clay cement Authors: Liu, Mingqing Abstract: The large-scale production of cement worldwide contributes to 6-8% of global anthropogenic CO2 emissions. Among supplementary cementitious materials (SCMs), limestone and calcined clay are abundant and widely available yet remain underutilised. Limestone Calcined Clay Cement (LC3) enables up to 60% clinker replacement, achieving approximately 40% lower CO2 emissions compared with ordinary Portland cement (OPC). LC3 containing 40% calcined kaolinite develops higher strength than OPC from 7 days onwards. However, LC3 shows lower early-age strength and a slower rate of strength gain compared with OPC. To address this limitation, this thesis focuses on enhancing the early strength of LC3 through the incorporation of nanomaterials and triethanolamine (TEA). In addition, the effects of nano-SiO2 (NS) and calcined clay content on the durability and rheological properties of LC3 are also investigated. Chapter 4 mainly investigates the effects of nano-Al2O3 (NA) and nano-SiO2 (NS) on the hydration and mechanical properties of LC3. Gypsum optimisation is carried out first with a moderate dosage of 2% by weight, yielding the highest cumulative heat release. Results suggest that NA exhibits both pozzolanic and nucleation effects, whereas nano-TiO2 (NT) functions only as a nucleation site. However, the beneficial contribution of NA is largely restricted to the very early stages of hydration (within the first day) and even leads to reduced strength in LC3 at later ages. When NS is incorporated into LC3, it is observed to accelerate hydration, reduce workability, and enhance strength at all ages, with particularly significant gains at early ages. Furthermore, this chapter examines the influence of calcined clay (Cc) content on LC3 hydration. A higher Cc content enhances the pozzolanic reaction and improves compressive strength across all curing ages. While increasing Cc raises the total porosity of LC3, it simultaneously refines the pore structure by increasing the proportion of fine pores, despite a concurrent rise in large pores. Chapter 5 evaluates how NS and Cc influence the sulfate resistance of the LC3 system. The incorporation of NS improves dimensional stability during sulfate exposure, as evidenced by reduced relative mass and length changes. While NS has minimal influence on ettringite formation under standard curing, it significantly inhibits ettringite generation when the system is subjected to sulfate attack. Increasing the Cc content also enhances sulfate resistance, reflected in lower mass and length variations. Under standard curing, LC3 mixes with Cc achieve higher long-term strength than those without Cc. However, in Na2SO4 solution, only the blend containing 30% Cc shows a clear early age strength improvement, and the long-term strength benefit remains limited. Sulfate exposure promotes the formation of mono-carboaluminate (Mc), but its overall content decreases as Cc levels rise. Although adding Cc increases ettringite formation across all blends, its influence differs between curing conditions: under standard curing, higher Cc has little effect on ettringite content, whereas under sulfate attack, it distinctly suppresses ettringite formation. Chapter 6 studies the effects of nano-SiO2 (NS) on the rheological behaviour of the LC3 system. Results reveal that increasing NS dosage leads to higher plastic viscosity as well as greater static and dynamic yield stress. Similarly, extending the resting time increases viscosity and both yield stresses (static and dynamic). All mixes exhibit a gradual decrease in phase angle over time, indicating a transition from viscous (fluid-like) to elastic (solid-like) behaviour. Chapter 7 explores the individual and synergistic effects of NS and TEA on the hydration and hardened properties of the LC3 system. The findings show that NS primarily enhances the hydration of the silicate phase, whereas TEA regulates the timing of the silicate peak. For the aluminate peak, both NS and TEA advance its occurrence, with NS exerting a stronger influence. Either additive alone increases the intensity of the aluminate peak, while their combination produces an even stronger synergistic effect. TEA enhances LC3 strength at all ages, whereas NS contributes mainly to early age strength. The synergy of NS and TEA produces more pronounced improvements than either additive alone. Furthermore, TEA primarily alters pore size distribution rather than total porosity, driving a shift from larger to finer pores. The synergistic blend of NS and TEA achieves the most favourable pore size distribution. Description: This thesis was submitted for the award of Master of Philosophy and was awarded by Brunel University London Wed, 01 Jan 2025 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/32798 2025-01-01T00:00:00Z http://bura.brunel.ac.uk/handle/2438/32415 Title: Data-driven modelling of nitrous oxide production in wastewater treatment processes using neural ordinary differential equations Authors: Huang, Xiangjun Abstract: Nitrous oxide (N₂O) emissions from wastewater treatment facilities pose a significant environmental challenge. This study proposes a novel data-driven modelling approach using emerging neural ordinary differential equations (NODE) to capture the complex dynamics of N₂O production in typical activated sludge processes. The author established an experimental simulation platform, based on the BSM1 (benchmark simulation model no.1) plant, with the ASMG1 (activated sludge model for greenhouse gases no.1) mathematical model. This platform generates simulated monitoring data and validates the model. The author then proposes NODE-based models, analogous to traditional biokinetic models, capable of capturing the complex dynamics of N₂O generation through learning from process monitoring data. However, two primary challenges need to be overcome. First, to address inherent stiffness in the underlying dynamics, the author proposes a 𝗽𝗮𝗶𝗿𝗲𝗱 𝗻𝝾𝗿𝗺𝗮𝗹𝗶𝘀𝗮𝘁𝗶𝝾𝗻 𝗺𝗲𝘁𝗵𝝾𝗱 for training stability. Additionally, an 𝗶𝗻𝗰𝗿𝗲𝗺𝗲𝗻𝘁𝗮𝗹 𝘁𝗿𝗮𝗶𝗻𝗶𝗻𝗴 𝘀𝘁𝗿𝗮𝘁𝗲𝗴𝘆 was introduced, starting from a 𝗰𝝾𝗹𝗹𝝾𝗰𝗮𝘁𝗶𝝾𝗻 𝗺𝗲𝘁𝗵𝝾𝗱 to establish a robust foundation, followed by refinement using the 𝗱𝗶𝗿𝗲𝗰𝘁 𝝢𝝤𝗗𝗘 𝗺𝗲𝘁𝗵𝝾𝗱 for enhanced accuracy and efficiency. Second, as monitoring data in wastewater plants typically contain confounding factors from continuous influent variations and operational adjustments, representing 𝗲𝘅𝝾𝗴𝗲𝗻𝝾𝘂𝘀 𝗲𝘅𝗰𝗶𝘁𝗮𝘁𝗶𝝾𝗻𝘀 to the dynamics to be captured, therefore the training procedures was extended to account for these external influences. The approaches were validated on the established platform. The results demonstrate the effectiveness of the NODE-based model in capturing the intricate dynamics of N₂O production in wastewater treatment. This research presents a promising new avenue for data-driven modelling of N₂O in wastewater treatment, with the potential to improve process optimisation and emission control strategies. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London Wed, 01 Jan 2025 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/32415 2025-01-01T00:00:00Z http://bura.brunel.ac.uk/handle/2438/32411 Title: The self-healing mechanisms of bacterial cementitious materials via novel isolated ureolytic bacterium species Authors: Yousef, Wasef Abstract: The self-healing approach used in this study is based on the urease hydrolysing bacterium, namely, Bacillus Sphaericus. The scope of the work is diverse as it combines and brings together both aspects of the bioengineering and civil engineering in order to provide better understanding of the self-healing mechanisms that lie behind the yielding of the calcium carbonate precipitation. The initial stage of this study, comprised of collecting different soil samples from different alkaline sources to extract and isolate urease bacterium species. In addition, a collection of more than 100 different bacterial strains belong to bacillus Sphaericus were screened for the presence of urease enzyme and ability to produce copious amount of calcium carbonate under extreme alkaline conditions. In-vitro calcium carbonate precipitation experiments were performed to stress the selected bacterial strains prior to the application for the self-healing mortar. Parameters such as temperature, pH, shaking conditions, ability to form endospores and the production of copious amount of calcium carbonate were placed under scrutiny. The biochemical properties of the selected bacterial strain were studied and investigated further by monitoring the evolution in pH, the production of ammonium, insoluble and soluble calcium and the colony forming unit. Following the characterisation, three strains were promoted forward for the use of self-healing mortar. In-vitro calcium carbonate perception in broth state showed that the yielding of CaCO3 was maximum in the case of strain 89 and strain 67 at 0.5932g/100ml and 0.8398 g/100ml, respectively. The need for an encapsulating material that provides suitable environment for the bacteria to endure the mechanical and physical forces in addition to the high alkaline environment of the cement matrix, is indeed a key component towards the self-healing applications. As a result, the autoclaved aerated recycled concrete (AAC) aggregates were selected for this study, due to the high porous structure which implies high absorption properties. Three healing systems were proposed for the application of the self-healing mortar. The first approach comprises of bacterial spores impregnated under vacuum into the AARC aggregates along with a suitable nutrient designed specifically for maximum yielding of calcium carbonate precipitation. The second approach comprised of a three-component healing system with the introduction of a mixed culture to enhance the healing capacity in addition to providing reinforcement for the cement matrix. The third approach comprised of direct incorporation of different bacterial cells into cement mortar to test for the capacity of the strain to heal cracks under high alkaline environment. Mortar specimens were cracked at 28 days of curing, ranging from 0.127 to 0.875mm, the introduction of the three-healing system provided promising results in regard to healing cracks of 0.875mm over the period of 289 days of curing. Direct incorporation of bacterial strains at different concentrations 107cells/ml and 108cells/ml showed the tendency to heal cracks of 0.127 and 0.253mm, respectively. Furthermore, direct incorporation of bacterial cells into the cement matrix, supported the analysis that urea hydrolysing bacteria is indeed an enzymatic activity. Two key enzymes were defined and strongly linked to the calcium carbonate precipitation process that is the urease enzyme and the carbonic anhydrase enzyme, where the latter is a zinc enzyme that catalyses the conversion of calcium dioxide into carbonate acid and ultimately promotes further insoluble calcium carbonate precipitation. The introduction of a three-component healing system showed enhanced healing capacity, Direct Incorporation of 107cells/ml with 30% impregnated aggregates showed the capacity to partially heal cracks of 0.791mm by 28.3% over 14 days and 100% over 28 days healing period. Increasing the number of cells showed expected higher healing efficiency, specimens in set 22.1B were able to completely seal cracks of 0.875mm by 99.085 % over the period of 28 days. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London Wed, 01 Jan 2020 00:00:00 GMT http://bura.brunel.ac.uk/handle/2438/32411 2020-01-01T00:00:00Z