Decarbonising industry and the economy is essential to improve the balance between our ecological footprint and the planet’s renewable resources. This would provide the best possible chance for humanity to mitigate the effects of climate change. Consequently, we need to rethink the way we build our cities. And to do this, we need to talk about cement.
Cement, the ‘glue’ in concrete, is the durable, waterproof and ubiquitous material upon which modern civilisation is built. Concrete is second only to water in terms of commodity use, and the world produces more than 10 billion tonnes of it each year.
Cement production alone (excluding other aspects of construction) accounts for around 8% of global CO₂ emissions, about half of which results from chemical reactions inherent in the production process. As other industries such as energy and agriculture reduce their share of emissions, cement production may account for nearly a quarter of all human-driven CO₂ emissions by 2050.
Modern alkali-activated cements (AAC) can enhance physical properties, and reduce associated CO2 emissions by >80%, compared to Portland cement. Additionally, these cements are produced primarily from supplementary cementitious materials (SCM) which are typically industrial by-products such as metallurgical slags, or naturally abundant minerals such as clays, further enhancing their sustainability.
These cements require an alkali ‘activator’ to provide a high pH in the fresh cement paste and drive reaction, setting and hardening. However, concentrated alkali solutions exhibit high viscosities and complex crystallisation behaviour, which dramatically affects the reaction mechanisms and kinetics, and physical properties of the resultant cements, even with only minor changes in mix formulation. A detailed understanding of crystallisation processes, fluid-particle and particle-particle interactions is urgently required for these next-generation low-carbon cements, to enable quality control and make them practical for use in large-scale construction.
This PhD uses in-situ surface-specific techniques, spectroscopic and microstructural characterisation to examine these interactions in AAC produced using a suite of alkali solutions and SCMs. Currently underutilised SCMs (e.g. basic oxygen furnace, legacy slags) are investigated, and benchmarked against AAC produced using blast furnace slag (industry standard). The knowledge obtained will be used to design novel AAC formulations with enhanced performance. This will drive implementation, and help decarbonise cement production.
We will examine how crystallisation processes, fluid-particle and particle-particle interactions affect (i) dispersion, fluidisation, and rheology of the fresh cement paste, (ii) reaction and setting, and (iii) physical property development of low-carbon AAC. We will use this information to design and test new AAC formulations for enhanced performance and quality control.
Specifically, it will develop a mechanistic understanding of crystallisation processes, fluid-particle and particle-particle interactions, by experimentally assessing:
- Surface chemistry of the activating solution and fresh cement paste.
- Reaction and setting, and fresh-state physical characteristics of the cements.
- Evolution of cement structure, phase assemblage and durability.
This will show how the nature of the raw materials affect: 1) dispersion, fluidisation, and rheology, 2) reaction and setting, and 3) physical property development. This will enable optimisation of cement formulations for enhanced sustainability, performance and durability, and hence drive industrial innovation.
Based in the Departments of Chemical and Biological Engineering, and Materials Science and Engineering, the successful candidate will be joining a team of multidisciplinary researchers at the University of Sheffield to develop research and innovation for decarbonisation. The successful applicant will also benefit from industrial supervision by DB Group (Holdings) Ltd. They will benefit from being a member of a friendly and collegial group with world-leading expertise and facilities.
The PhD researcher will also undertake a 3 to 6-month secondment in with DB Group (Holding) Ltd. their UK R&D site for cement research. During this industrial secondment, the PhD researcher will evaluate research findings to date as relevant to DB Group’s cement product-focused business needs.
The Sustainable Materials at Sheffield group (in the Department of Chemical and Biological Engineering) and the Cements@Sheffield group (in the Department of Materials Science & Engineering) are world-leading research teams, located in highly-rated and very successful departments, building from over 100 years of history in cements research at Sheffield. We investigate interesting and important cements and related materials for applications in nuclear and infrastructure sectors, publish our work in the leading journals and conferences in the field, and take great pride in the fact that alumni have gone on to the highest levels of success in both academia and industry.
Both the Department of Chemical and Biological Engineering and the Department of Materials Science & Engineering rank among the top in the UK, and have among the highest levels of research income.
Start Date of Studentship: 25th Sept 2023
Please see this link for information on how to apply: https://www.sheffield.ac.uk/cbe/postgraduate/phd/how-apply. Please include the name of your proposed supervisor and the title of the PhD project within your application. For more details contact Dr Brant Walkley at [Email Address Removed].
This interdisciplinary project spans chemical engineering, materials engineering, and inorganic chemistry. It is ideally suited to a mature, highly numerate graduate with good communication skills, a passion for scientific and engineering research, and enthusiasm to tackle globally relevant and uniquely challenging chemical engineering and chemistry problems.
Applicants should have a first or upper second class UK honours degree or equivalent in a related discipline (Chemical/Materials/Environmental/Civil Engineering, Materials/Inorganic Chemistry or Mineralogy/Geochemistry). A strong undergraduate background in chemical/materials engineering and inorganic chemistry, with an interest in driving sustainability, is desired. If English is not your first language then you must have an International English Language Testing System (IELTS) average of 6.5 or above with at least 6.0 in each component, or equivalent. Please see this link for further information: https://www.sheffield.ac.uk/postgraduate/phd/apply/english-language.
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