Subject matter

The use of natural mineral resources has been the basis of growth in civil infrastructure for thousands of years. At the same time, the exploitation of natural resources and the pollution associated with their extraction and processing have stretched the limits of our natural habitat, putting significant pressure on the environment and human well-being. There are now 8 billion people on Earth and, according to the United Nations, the world’s urban population has quadrupled since the 1950s, reaching 4 billion today, and with an estimated 7 billion people living in cities by 2050. To sustain this rapid urbanisation rate, billions of tonnes of construction materials are required annually. All evidence and projections suggest that civil infrastructure growth will keep expanding to meet the needs of modern urban societies, including essential development for poverty reduction and provision of necessities to the billions currently living in under-served communities. A recent report from the Organisation for Economic Co-operation and Development (OECD) projects a rapid growth in the production and use of construction materials in the next 40 years. This translates into a massive demand for virgin natural raw materials that will have a detrimental effect on the environment, depleting natural resources and causing large scale destruction of landscapes. The manufacture of cement is a process that utilises enormous amounts of raw materials and energy, due to the sheer scale of the industrial processes required. Cement is the glue of most infrastructure assets and Portland cement has been the dominant binder worldwide for the past ~200 years and can never be displaced; however, with a shift towards performance-based standards and the environmental burden brought about by conventional cement manufacturing – a toolkit of cementitious materials opens up for use in various structural and non-structural applications; the cement community is shifting away from the notion of a need for a “one size fits all” general purpose cement. This enables a pool of raw materials waiting to be exploited in a sustainable and responsible manner.

The International Energy Agency, in its recently published roadmap for a sustainable transition in the cement and concrete industries, has strongly highlighted two important elements: (i) the need to switch to alternative raw materials by 2025 and (ii) to switch to alternative cementitious binders by 2035. This strategy is also promoted by the European Cement Association in its latest report on decarbonisation of cement. Billions of tonnes of mineral wastes (from mines, quarries, industrial processes, construction and demolition, and excavations for the construction of major infrastructure) are produced globally every year. The disposal of such waste is a major environmental challenge and liability. Mineral wastes are typically rich in SiO₂, Al₂O₃, CaO, MgO, and Fe₂O₃,  making them very attractive candidates to be used in the production of cementitious materials. In the last several years there is a growing interest in utilising such wastes in the manufacture of cement-based composites, particularly alkali-activated binders. Mineral wastes can offer a natural solution to a major problem and at the same time be diverted from landfill while their own environmental impact is mitigated. Upcycling such wastes in the production of cements is the most promising way to improve resource efficiency and material circularisation while maintaining our natural reserves of raw materials and significantly reducing CO₂ emissions by reducing the dependency on heavy processing of pristine raw materials (such as CaCO₃) for the manufacture of cements and aggregates.

The purpose of this new RILEM Technical Committee (TC) is to compile the plethora of available information and knowledge on the reuse and upcycling of all mineral wastes in cementitious matrices. The proposed TC will investigate the landscape of mineral wastes by developing an inventory and map of global resources. In addition, it will explore the state-of-the-art of utilisation of these wastes in various binders. The TC will also look into procedures that can be done at the source that will increase the uptake of mineral wastes as well as considerations around life cycle and end-of-life of composites containing the mineral wastes, i.e., recycling after upcycling.  A TC on this vast growing area will bring together researchers from different parts of the world and will contribute considerably to the integration of knowledge and practices. This has the potential to lead on the standardisation of materials and processes which in turn will help the quick uptake of the technology. The proposed committee will create the suitable environment for a wide and systematic approach on the emerging area of developing sustainable cementitious composites. Furthermore, the proposed TC complements existing MCP and CCL committees, aiming to provide a different angle of approach as to how bulk volumes of mineral wastes can be repurposed in cementitious matrices; this TC will not look at mineral carbonation for CO₂ capture or use as SCMs and will also not focus on calcined kaolinitic clays for use as SCM.

Terms of reference

The proposed life of this TC is five years starting from February 2023. The overview of the proposed timeline and TC activities are as follows:

Years 1 to 5: Detailed review of published studies and relevant technical information. Development of a topical collection in Materials & Structures on the upcycling of mineral wastes in cementitious matrices.

Years 2 to 3: Planning and organising an international workshop on utilisation of mineral wastes in cementitious matrices. This can be in one of the main annual RILEM events (spring convention and RILEM week).

Years 3 to 5: Development of technical and practical guidelines for upcycling mineral wastes in cementitious matrices.

The TC roster is expected to include approximately 50 individuals around the world representing academic institutions, research centres and relevant industries. Membership to the committee will be based on interest on the area as well as on experience on the subject matter. Participation of PhD students and early-stage researchers will be encouraged.

The prepared guidelines and state-of-the-art report are expected to significantly accelerate construction materials  circularisation at scale. In this regard, the work of the TC is highly relevant to industry.

Detailed working programme

The work of the committee will be organised in working groups (WG). The work of the individual WGs will be further defined once the committee comes together and individuals are allocated to specific tasks.

WG1 – Develop mineral wastes inventory/maps and classification

Focus on developing a machine-actionable database of available legacy and recent mineral wastes around the world, including the production rates, and the subsequent mapping of their raw properties and mineralogy for use with each other as well as evaluate potential applications. This will provide a global outlook of available compounds and will enable strategy and policy development. TC members will contribute by providing the information for mineral wastes that exist in their regions.

WG2 – Utilisation of mineral wastes in clinker-derived cementitious matrices

Focus on production of clinker and manufacturing of SCMs. The committee will investigate mechanochemical, thermal, and chemical treatments of mineral wastes that will allow modification of their crystal structure which yield them eligible to be used either in the production of clinker or SCM. The TC will draw information from the existing state-of-the-art including published unconventional clinker chemistries and will develop the basis for formulating protocols and procedures of production.   

WG3 – Utilisation of mineral wastes in alkali and acid activated cements

Focus on alkali and acid activated materials. Similar to traditional cementitious systems, the committee will investigate any processing requirements or direct usage of mineral wastes in alkali or acid activated binders. The existing state-of-the-art will be thoroughly investigated and protocols and recommendations will be developed.

WG4 – Pre-processing, Separation, and Environmental considerations

Focus on presence of and removal of harmful or unwanted elements as well as immobilisation, design to recycle, life cycle assessment, end-of-life, and occupational exposure/H&S. Existing state-of-the-art will be investigated alongside with standard practice of designing components and materials that incorporate wastes. National and international standards will be assessed, and recommendations will be drawn for the safe use of mineral waste.

The TC will maintain a cloud-based repository for data storage and sharing at the University of Hertfordshire’s cloud server. Several publications will be produced; the main goal of the committee is to produce the technical guidelines and present the state-of-the-art to accelerate the alternative raw materials revolution. These documents will gradually develop throughout the lifetime of the TC.