The construction industry urgently requires a resilient information system for effective coordination of data transmission among various stakeholders, including both the public and private sectors. Such an advanced digital solution would not only enhance transparency along the value chain but also improve both the quality of and confidence in recycled materials. Achieving circularity and reducing environmental impact are closely tied to the efficient management of material flows and life cycles. Within this context, Material Passports (MPs) are posited as a foundational element, particularly when integrated with a digital database. This integration is particularly beneficial for increasing the circularity of concrete, beginning with end-of-life concrete, a major contributor to global construction and demolition waste. MPs effectively transmit crucial information about the quality of recycled aggregates, thereby enabling their use in future construction projects. This study explores the feasibility of employing Radio Frequency Identification (RFID) technology as an MP, aiming to enhance sustainability in the concrete industry by improving transparency, traceability, and data reliability in the recycled concrete supply chain. Extensive laboratory tests carried out in three distinct experimental phases revealed that RFID tags exhibit remarkable resilience to mechanical stress typical in the supply chain and consistently maintain readability when embedded in concrete. The water content in concrete samples was identified as a significant factor influencing initial tag readability, although readability improved over time. Other factors, such as the type of aggregates, particle size distribution, and proximity to steel rebar, had minimal to modest impacts on tag performance. Additionally, the study confirmed that the readability of RFID tags remains robust at typical transport speeds, which highlights the potential of an RFID-based system in advancing supply chain management. This study provides a solid foundation for future research in this evolving area.

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This study addresses a critical gap in circular construction practices by assessing the use of high-quality Recycled Coarse Aggregates (RCA) from end-of-life concrete on an industrial scale. Unlike previous studies, which predominantly relied on theoretical mix designs or laboratory-level experiments, this research focuses on real-world applicability, employing commercially produced RCA and conventional production methods in industrial settings to identify upscaling challenges. Advanced Dry Recovery technology is utilized to produce high-quality RCA for both ready-mix and prefab concrete production. To ensure practical relevance, the research examines three water-to-cement ratios for ready-mix concrete and three strength classes for prefab concrete, all prepared and cast in a commercial setting using standard industrial practices. The results show that by selecting the appropriate application for RCA, there is potential for concrete companies to produce mixes using 100% RCA that meet standard requirements in terms of fresh, mechanical, and durability properties without the need for extra treatments or specific mixing methods, particularly when the water absorption of RCA is less than 4%. Achieving optimal performance requires adjustments in the mix design, specifically by considering the effective water-to-cement ratio. Additionally, the study underscores the impact of the parent concrete's properties on the RCA quality. This research not only demonstrates the feasibility of employing RCA in industrial-scale concrete production along with its associated challenges but also highlights the potential for enhancing circularity in the construction industry through large-scale adoption of RCA, thereby contributing to sustainable and circular construction practices.

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This study focuses on formulating the most sustainable concrete by incorporating recycled concrete aggregates and other products retrieved from construction and demolition (C&D) activities. Both recycled coarse aggregates (RCA) and recycled fine aggregates (RFA) are firstly used to fully replace the natural coarse and fine aggregates in the concrete mix design. Later, the cement rich ultrafine particles, recycled glass powder and mineral fibres recovered from construction and demolition wastes (CDW) are further incorporated at a smaller rate either as cement substituent or as supplementary additives. Remarkable properties are noticed when the RCA (4–12 mm) and RFA (0.25–4 mm) are fully used to replace the natural aggregates in a new concrete mix. The addition of recycled cement rich ultrafines (RCU), Recycled glass ultrafines (RGU) and recycled mineral fibres (RMF) into recycled concrete improves the modulus of elasticity. The final concrete, which comprises more than 75% (wt.) of recycled components/materials, is believed to be the most sustainable and green concrete mix. Mechanical properties and durability of this concrete have been studied and found to be within acceptable limits, indicating the potential of recycled aggregates and other CDW components in shaping sustainable and circular construction practices.

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Currently, natural resources are consumed at an alarming rate than their production (United Nations Environment Programme, 2014). This imposes unprecedented pressure on the environment. The problem seems to get worse with the present increase in population and demand for infrastructures. To alleviate these and other related problems, a circular approach to construction material flow is crucial. Recycling construction and demolition wastes (C&DW) to generate high-quality materials is essential to ensure materials circularity in the construction sector. This article, therefore, describes the development of two large-scale technologies called Advanced Dry Recovery (ADR) and Heating Air classification System (HAS). ADR and HAS are industrial-scale technologies aimed to recycle End-of-Life (EoL) concrete into coarse, fine and ultrafine particles. While ADR is used to sort out clean coarse aggregates, HAS is used to produce clean fine aggregates by heating and separating the ultrafine hydrated cement components. The process parameters and the quality of aggregates are briefly described. Accordingly, concrete made of recycled coarse and fine aggregates displays comparable mechanical properties as the reference concrete which is made of natural aggregates. Both technologies are designed to be mobile so that EoL concrete wastes are processed at the site of demolition or close to ready-mix concrete plants, reducing the heavy traffic related to construction activities. These technologies, in general, have a potential in increasing sustainability and thereby greening the construction sector. This is by far a convenient contribution towards sustainable development and a big step towards closing the recycling loop in the construction sector.@en

Circular concrete is one of the main focuses of current research in the construction industry. This is due to the fact that the construction sector is facing several pressures from society and policymakers. In an attempt to assure the sustainability of the sector, different research options have been put in place. Among them, the use of recycled aggregates and recycled cement is a subject of current research.

The objective of this study is to optimize the particle size distribution of aggregates and understand the compaction of concrete made of recycled aggregates and recycled cement, so as to reduce the amount of cement used in the new concrete mix. Particle size optimization is aimed at improving the density of concrete made of regularly packed aggregates and the distribution of voids, thereby improving its sustainability and strength. This could be achieved by optimizing the amount of water, the size of aggregates and fillers, and adjusting the amount of cement in the mix design.

In this specific study, recycled aggregates (<12mm) are used along with natural aggregates of different sizes (<12mm and <16 mm). The role of maximum aggregate size and the effect of the complete substitution of natural aggregates with recycled aggregates have been studied. Furthermore, the effects of compaction, the role of internal pores, and aggregate size distribution on the mechanical properties of hardened recycled concrete are also investigated. Three recipes have been designed to employ different types of aggregates. The water-to-cement ratio of the recipes was adjusted based on the magnitude of the slump. The recipes were cast in various procedures associated with different durations of vibration to understand the role of vibration on their compressive strength after 7, 28, and 91 days.

After optimizing the duration of vibration and casting concrete samples, the selected specimens with natural aggregates and recycled aggregates were scanned by a macro-CT scanner to comprehend the spatial distribution of aggregates and air bubbles inside the hardened concrete. Results indicate that the duration of vibration was observed to be critical depending on the type and size of aggregate. Despite the direct relationship between vibration and internal pores, the impact seems to be negative beyond a certain time. The compaction and mechanical properties of concrete made of recycled aggregates need more vibration compared to natural aggregates.@en

The ever-increasing interest on sustainable raw materials has urged the quest for recycled materials that can be used as a partial or total replacement of fine fractions in the production of concrete. This paper demonstrates a modelling study of recycled concrete waste fines and the possibility of turning them into active constituents for the production of concrete. When construction demolition waste (CDW) fines with particle size 0 - 4mm are exposed to a hot environment, different reactions will occur, especially dehydration and phase changes. A one- dimensional (1D) transient model is developed to predict the conversion of the hydrated concrete fines into their dehydrated state, in which the key processes inside the particle and at the boundary layer outside the particle are properly addressed. The model predicts a final composition of the particle that resembles cement clinker, which means a high potential for reuse in manufacturing concrete. Finally, model results for the mass loss during conversion are experimentally validated using thermogravimetric study. @en

After a decade of intensive research into the recycling of End-of-Life (EOL) concrete into high-grade new concrete, largely supported by funding from the European Commission, it appears that a circular economy for concrete is techno-economically feasible. A collection of advanced technologies, in particular smart demolition for clean mono-flows of EOL concrete, new attrition and classification processes for removing the fine, moist-, lights- and cement-rich fraction from coarser aggregates, sensor sorters for removing larger pieces of wood, plastics and metals from recycle aggregate, green thermal treatment for concentrating and purifying the EOL cement paste and Laser-Induced Breakdown Spectroscopy tools for verifying the quality of input materials for the mortar facilities, have been put into place to make recycled concrete in some technical aspects even superior to concrete made from river gravel. And at competitive costs. Is this enough to make the transition to circular concrete into a success? Not necessarily. The integration of circular concrete into the routine of construction requires new procedures and agreements between stakeholders to avoid risks in producing an extremely cheap but at the same time strongly quality-guaranteed concrete commodity from a new and variable feedstock. It is argued that extremely tight quality checks should be installed in combination with a commitment of the entire chain to gently increase the fraction of recycled materials into new concrete as the EOL concrete flow grows as a consequence of phasing out buildings from the post-war boom.@en