Forward-looking life cycle assessment of novel bauxite residue-incorporated cementitious materials
File(s)
Author(s)
Georgiades, Maria
Type
Thesis
Abstract
Bauxite residue (BR) is emerging as a raw material with significant potential for developing cementitious materials, including supplementary cementitious materials (SCMs). While laboratory and pilot-scale technologies have shown promise for incorporating BR into cement, their environmental performance remains poorly explored. Therefore, forward-looking environmental assessments are necessary to evaluate the potential benefits of BR utilisation in cements, which is explored in this thesis. First, an ex-ante life cycle assessment (LCA) was conducted to assess the environmental performance of BR vitrification technology to produce a reactive SCM at different scales. Upscaling laboratory to pilot and industrial scales reduced environmental impacts by 83% and 94%, respectively. Various upscaling approaches were explored, showing that with appropriate parameters, proxy modelling can perform comparably to complex process models, supporting its suitability in early-stage assessments with limited data. Second, prospective LCA of traditional cement production was performed, incorporating several decarbonisation measures: increasing clinker substitution, increasing alternative fuels, improving kiln efficiency, carbon capture and storage (CCS), and electricity grid decarbonisation. The results showed that clinker substitution could potentially reduce CO2-eq. emissions by 42% between 2020 and 2050. Combining all decarbonisation measures could reduce CO2-eq. emissions to below 0.01 kg per kg of cement by 2050. Third, ex-ante LCA was conducted on three BR processing technologies: (i) co-calcination with kaolin clay, (ii) vitrification, and (iii) reductive smelting, producing BR-based SCMs for up to 30% clinker replacement. Environmental performance was influenced by energy requirements and sources, raw material composition, and clinker replacement ratio. Composite cements were analysed by combining environmental and mechanical performance, showing that optimising fineness and material composition can reduce impacts without compromising strength. The thesis demonstrated the importance of early-stage environmental assessments in identifying hotspots, guiding optimisation, and supporting upscaling. Its findings offer benchmarks for comparing emerging BR technologies with conventional practices and quantifying their environmental benefits.
Version
Open Access
Date Issued
2024-10-17
Date Awarded
01/07/2025
License URL
Advisor
Myers, Rupert J.
Cheeseman, Christopher
Sponsor
European Commission
Grant Number
Grant Agreement No. 958208
Publisher Department
Department of Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)