Environmental impacts and decarbonization strategies in the cement and concrete industries

The use of cement and concrete, among the most widely used man-made materials, is under scrutiny. Owing to their large-scale use, production of cement and concrete results in substantial emission of greenhouse gases and places strain on the availability of natural resources, such as water. Projected urbanization over the next 50–100 years therefore indicates that the demand for cement and concrete will continue to increase, necessitating strategies to limit their environmental impact. In this Review, we shed light on the available solutions that can be implemented within the next decade and beyond to reduce greenhouse gas emissions from cement and concrete production. As the construction sector has proven to be very slow-moving and risk-averse, we focus on minor improvements that can be achieved across the value chain, such as the use of supplementary cementitious materials and optimizing the clinker content of cement. Critically, the combined effect of these marginal gains can have an important impact on reducing greenhouse gas emissions by up to 50% if all stakeholders are engaged. In doing so, we reveal credible pathways for sustainable concrete use that balance societal needs, environmental requirements and technical feasibility

Hydration and mixture design of calcined clay blended cements: review by the RILEM TC 282-CCL

The RILEM technical committee 282-CCL: Calcined Clays as Supplementary Cementitious Materials, investigates all the aspects related to calcined clays, from clay exploration and characterization to calcination process, hydration reactions and concrete properties. This white paper focuses on the hydration mechanisms of calcined clay-blended Portland cements, covering both 1:1 and 2:1 calcined clays. The pozzolanic reaction of calcined clay is detailed, and the main reaction products are described. The differences observed depending on the clay type are also discussed, as well as the potential influence of the secondary phases present in calcined clay. The factors controlling and limiting the reaction of calcined clay are investigated, evidencing the role of porosity saturation and refinement of the microstructure. The complete characterisation of the hydration of calcined clay cements is made possible by the determination of the reaction degree of calcined clay. Several methods are compared to estimate the extent of calcined clay reaction. The influence of clinker and limestone mineralogy are also discussed. Finally, guidelines for optimising the mixture design of calcined clay blended cements are provided, with special attention to sulphate adjustment and clinker factor

Clay calcination technology: state-of-the-art review by the RILEM TC 282-CCL

The use of calcined clays as supplementary cementitious materials provides the opportunity to significantly reduce the cement industry’s carbon burden; however, use at a global scale requires a deep understanding of the extraction and processing of the clays to be used, which will uncover routes to optimise their reactivity. This will enable increased usage of calcined clays as cement replacements, further improving the sustainability of concretes produced with them. Existing technologies can be adopted to produce calcined clays at an industrial scale in many regions around the world. This paper, produced by RILEM TC 282-CCL on calcined clays as supplementary cementitious materials (working group 2), focuses on the production of calcined clays, presents an overview of clay mining, and assesses the current state of the art in clay calcination technology, covering the most relevant aspects from the clay deposit to the factory gate. The energetics and associated carbon footprint of the calcination process are also discussed, and an outlook on clay calcination is presented, discussing the technological advancements required to fulfil future global demand for this material in sustainable infrastructure development

The development of microstructure during the hydration of Portland cement

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Nanotechnology and Cementitious Materials

The relevance of nanotechnology and more specifically nanoscience to cementitious materials is discussed. Some examples are given of the influence of nanosciences on our understanding of cementitious materials and its impact on the applications of these materials