Multi-scale engineering of alkali-activated concretes for sustainable infrastructure

Infrastructure is the foundation of the society and economy of every nation, and enables us to enjoy a high standard of living. Currently 3.5bn people live in urban areas, and this will continue to rise, particularly in developing countries, reaching 6.2bn people by 2050. The provision of infrastructure and housing poses great challenges to be resolved in the coming years, but also offers a unique opportunity to drive significant global change, with the development of cities and the improvement of living standards to eliminate poverty and promote social inclusion being essential for global economic growth.

The enormous amount of resources necessary to fulfil the world's infrastructure requirements, and the urgent need to mitigate climate change, mean that it is essential to move from traditional ways of providing infrastructure (which involve the use of cement, steel and other resources, and emit large volumes of CO2), to more sustainable ways. This will safeguard our future global society.

The worldwide demand for Portland cement (a key component of concrete) has doubled in the past 10 years, to more than 4 billion tonnes per year, and this will continue to rise in the coming decades. This accounts for 8% of all worldwide CO2 emissions, and this could increase to as much as 25% by 2050. There is an urgent need for the UK, and the international community, to take up low-carbon best practices as we design and build infrastructure, so that significant reductions in carbon emissions can be achieved rapidly, and a shift towards a low-energy sustainable construction industry occurs.

This Early Career Fellowship research focuses on the design, characterisation and assessment of one of the most promising low-carbon candidates that can be used in place of Portland cement, to produce sustainable and durable concretes. These materials, called alkali-activated cements, can offer carbon emissions savings of 40-80% compared to Portland cement, when used to make a concrete with similar or better performance. However, despite this potential, the performance of alkali-activated materials in the field is unproven, and the processes that are now used for their production also face challenges that need to be resolved for the future-proofing of this technology.

So, further research is urgently required to prove that these materials can be produced by sustainable processes using highly available resources, and then serve well under challenging conditions, over periods of decades or more. This particularly means that we must understand the ability of potentially damaging chemical species to move through alkali-activated cements (either through the material itself, or through any cracks which may form as the material shrinks or is damaged). This lies at the heart of the understanding of concrete durability, and requires the development of advanced modelling tools to predict the long-term performance of concretes that are made from these new cements, moving beyond the timescales that can be accessed in the laboratory to describe real-world performance.

The central aim of this Fellowship research is to provide the scientific basis for the use of the UK's natural resources, as well as by-products from other industries such as the production and processing of metals, to produce high-performance, high-durability alkali-activated concretes using conventional and/or novel processes.

To achieve this, the Fellowship applicant and her team will use state of the art materials characterisation techniques to make connections between the way alkali-activated cements are produced, and their performance - moving the understanding 'from atoms to applications'. This will open a new pathway to building sustainable infrastructure for the future of the UK and worldwide, further strengthening the nation's current world-leading position in developing and using innovative cements, and opening opportunities for international connections and impact.

Impact

The main beneficiary of this Fellowship research will be the construction industry, as this research will help remove barriers to the usage of alkali-activated cements and concrete in practical large-scale applications. Through partnership with the leading UK producer of alkali-activated/geopolymer cements, Banah UK, as well as European and global experts in waste valorisation, materials and construction technology such as FehS (Institut für Baustoff Forschung) and Zeobond Pty Ltd, impact will be optimised through direct transfer of results into application at all levels of the industry supply chain, from raw materials to finished products.

Through partnership with these industry and commercial organisations, as well as the Swiss national laboratory EMPA (which is classified as an academic collaborator within the Fellowship research structure, but which nevertheless is extremely closely engaged with European and international industry), the Fellowship research results will be translated rapidly and effectively into state-of-the-art industry practice, in the UK and internationally. The ability to accurately assess, predict and model the durability performance of alkali-activated cements and concretes, from a technically validated basis, will bring a very high degree of impact in both academic and industry circles.

This information is the fundamental basis of performance-based standardisation, which are a crucial step to future development of standards enabling the use of innovative non-Portland cements in major infrastructure projects. The detailed modelling work which underpins this performance assessment will be disseminated through knowledge exchange workshops and direct engagement activities, including two specialised courses that will be delivered during the lifetime of the Fellowship research. The Fellowship team will also use these opportunities to gain input from partners and potential end-users regarding their priorities in terms of performance targets and key degradation mechanisms for in-service applications, and will incorporate this feedback into the modelling work.

The specific data underpinning these models will be made available to the developers of the international databases CEMDATA (thermodynamic data for cementitious systems), and SCEnAT and Ecoinvent (international references in the field of life cycle analysis) for inclusion in these widely used database tools, to maximise accessibility of the information to academic and industrial communities working on development and implementation of sustainable construction materials.

The Pathways to Impact plan also targets both social and technical aspects of implementing outcomes from the research in highly populated emerging countries such as Brazil, South Africa, India and Thailand through the current participation of the Fellowship applicant in Global Challenges Research Fund programmes. This will maximise the global impact of the Fellowship research, and will enable to identify future strategies for the development and application of alkali-activated materials, in different geographical regions.

The academic aspects of this dissemination will also be linked to two major events, where the Fellowship applicant is part of the organising and scientific committees: ECI Second International Geopolymers Conference, Tomar (Portugal), May 2018, and the RILEM Week and Annual Cement and Concrete Science Conference, Sheffield (UK), September 2020, hosted jointly by RILEM Association and the Cementitious Materials Group of IOM3.

Publications and outputs

• Adu-Amankwah S (2019) Influence of component fineness on hydration and strength development in ternary slag-limestone cements in RILEM Technical Letters
• Adu-Amankwah S. (2019) Particle size optimization in multi-component cement
• Alsaif A (2018) Durability of steel fibre reinforced rubberised concrete exposed to chlorides in Construction and Building Materials
• Alsaif A (2019) Freeze-thaw resistance of steel fibre reinforced rubberised concrete in Construction and Building Materials
• Bernal S.A. (2019) Natural and accelerated carbonation rates of alkali-activated slag/ fly ash blended concretes
• Bernal S.A. (2019) Rational design of alkali-activated materials
• Button K. (2019) Sodium sulfate activated slag-limestone composite cements
• Collier N (2019) Gaseous carbonation of cementitious backfill for geological disposal of radioactive waste: Nirex Reference Vault Backfill in Applied Geochemistry
• Criado M (2018) Slag and Activator Chemistry Control the Reaction Kinetics of Sodium Metasilicate-Activated Slag Cements in Sustainability
• Criado M. (2019) Structural changes in sodium carbonate activated slag binders induced by CO2 exposure