Recycling belite cement clinker from post-demolition autoclaved aerated concrete – assessing a new process

Increasing post-demolition autoclaved aerated concrete (pd-AAC) waste is mainly landfilled due to its physical properties and lacking recycling processes. A promising technology is the production of recycled belite cement clinker, which can partially substitute Portland cement clinker. This paper presents experimental data of recycled belite cement clinker production from pd-AAC that has been successfully demonstrated on technology readiness level 4–5 and its associated lifecycle assessment. Different supply chains for pd-AAC and energy are examined. The closed-loop pd-AAC recycling via the belite route that aims for Portland cement clinker substitution shows significant potential savings in environmental impacts. These savings could reach 0.77 kg CO2-Eq/kg pd-AAC compared to the status quo (landfilling) by using renewable electricity, and 0.34 kg CO2-Eq/kg pd-AAC by using natural gas. The gained reduction of around 13.5 % is significant considering that it is the result of substituting only 15.5 % of the overall input material

Comparison of different post-demolition autoclaved aerated concrete (AAC) recycling options

Autoclaved aerated concrete (AAC) is used as masonry blocks and prefabricated reinforced elements preferably in residential buildings. Due to its porous structure and mineral composition, it combines low thermal conductivity and fire resistance properties. Consequently, the popularity of AAC increases. However, due to significant AAC production volumes in many European countries since the 1960s and 1970s and given building lifetimes, strongly increasing post-demolition AAC waste volumes can be expected in the following decades. Recycling these post-demolition AAC wastes could protect primary resources and landfill capacities and reduce greenhouse gas emissions. But, recycling of post-demolition AAC is not yet established. The majority of the waste is landfilled even though landfill capacities have decreased and the legal framework conditions in Europe regarding a circular economy are becoming stricter. Therefore, new recycling options are needed. Current research approaches propose different open-loop recycling routes for post-demolition AAC, e.g. lightweight aggregate concrete, lightweight mortar, no-fines concrete, floor screed, animal bedding, oil- and chemical binders, and insulating fills for voids and interstitial spaces. Additionally, closed-loop recycling is possible and under research. Finely ground post-demolition AAC powder can be directly used in AAC production or can be chemically converted to belite (C2S) clinker to substitute primary cement in AAC production. These promising recycling options are compared regarding environmental and economic aspects. We find that the resource consumption is lower in all recycling options since post-demolition AAC helps to save primary resources. Furthermore, greenhouse gas emissions associated with the substituted primary resources are saved - especially when substituting primary cement in closed-loop recycling. In economic terms, increasing landfill costs could be avoided, which leaves a considerable margin for the cost of pre-processing, transport and recycling. The results can help decision-makers to implement circular management for AAC by fostering post-demolition AAC recycling and reducing its landfilling

Post-Demolition Autoclaved Aerated Concrete: Recycling Options And Volume Prediction In Europe

Autoclaved aerated concrete (AAC) is an increasingly used building material due to its exceptional thermal properties. Post-demolition AAC is mainly disposed in landfills because of lacking established recycling processes. However, the growing demand for sustainable products, greenhouse gas reduction, decreasing landfill capacities and new legal frameworks require recycling options for post-demolition AAC. Current research includes using post-demolition AAC recycling in the production of lightweight aggregate concrete, lightweight mortar, no-fines concrete, and floor screed. Even closed-loop recycling could be achieved by adding finely ground post-demolition AAC in the AAC production process or by producing belite cement clinker from post-demolition AAC as a substitution for Portland cement. Predicting the generation of post-demolition AAC volumes is crucial for a recycling and circular management of AAC. But, post-demolition AAC volumes in Europe are currently neither recorded in statistics nor investigated in comprehensive studies. Therefore, a post-demolition AAC prediction model is presented that quantifies post-demolition AAC on a national and European level. Results show low volumes in South East, Western, and Southern Europe as well as Scandinavia due to small market sizes. In North West and Central Europe, especially the UK (700,000 m³) and Germany (1,200,000 m³) in 2020 drive post-demolition AAC volumes. The most significant post-demolition AAC volumes occur in Eastern Europe, especially in Poland (1,800,000 m³) and Russia (3,900,000 m³) in 2020. While relative volumes between the regions stay similar, the absolute post-demolition AAC volumes in Europe will nearly double in the next decade from 12.3 to 22.0 million m³

Life cycle assessment of post-demolition autoclaved aerated concrete (AAC) recycling options

Autoclaved aerated concrete (AAC) is a widely used building material for masonry units, prefabricated reinforced components, and lightweight mineral insulation boards. Its low thermal conductivity and good fire resistance increase its popularity in residential buildings. Thus, post-demolition wastes are expected to increase in the future. However, post-demolition AAC (pd-AAC) is mainly disposed in landfills while landfill capacities decrease and legal framework conditions in Europe are tightening. This study performed life cycle assessments (LCA) of different pd-AAC recycling options and compared them to each other and to current landfilling to identify the best end-of-life handling of pd-AAC from an ecological perspective. The functional unit was 1 kg pd-AAC, and the system boundaries included pd-AAC at the demolition site, transports, pd-AAC treatment, and secondary production processes. Final products of the recycling process gained environmental credits/rewards for avoiding primary production using system expansion. Providing primary resources, primary production, and use phase were not in the scope of this study. Results show that especially closed-loop recycling of pd-AAC in AAC production has a high potential of improving environmental impacts. In the best recycling option (high substitution in AAC-0.35), potential savings per kg pd-AAC compared to landfilling reach up to 0.5 kg CO2-Eq, 7 MJ fossil resources, 0.005 mol H+-Eq (acidification), 0.17 CTU (freshwater ecotoxicity), 0.2 g P-Eq (freshwater eutrophication), 5.2 × 10-9 CTUh (carcinogenic effects), 4.4 × 10-8 CTUh (non-carcinogenic effects), 2.5 × 10-5 g CFC-11-Eq (ozone layer depletion), and 1.6 g NMVOC-Eq (photochemical ozone creation). Despite data uncertainties, recycling of pd-AAC is advantageous for several recycling options, including the production of AAC, light mortar, lightweight aggregate concrete, and shuttering blocks made from concrete without fine fractions (no-fines concrete). In Germany, up to 280,000 t CO2-Eq could have been saved in 2022 by pd-AAC recycling using different recycling options instead of landfilling

Wearable accelerometry-based technology capable of assessing functional activities in neurological populations in community settings: a systematic review

Background: Integrating rehabilitation services through wearable systems has the potential to accurately assess the type, intensity, duration, and quality of movement necessary for procuring key outcome measures. Objectives: This review aims to explore wearable accelerometry-based technology (ABT) capable of assessing mobility-related functional activities intended for rehabilitation purposes in community settings for neurological populations. In this review, we focus on the accuracy of ABT-based methods, types of outcome measures, and the implementation of ABT in non-clinical settings for rehabilitation purposes. Data sources: Cochrane, PubMed, Web of Knowledge, EMBASE, and IEEE Xplore. The search strategy covered three main areas, namely wearable technology, rehabilitation, and setting. Study selection: Potentially relevant studies were categorized as systems either evaluating methods or outcome parameters. Methods: Methodological qualities of studies were assessed by two customized checklists, depending on their categorization and rated independently by three blinded reviewers. Results: Twelve studies involving ABT met the eligibility criteria, of which three studies were identified as having implemented ABT for rehabilitation purposes in non-clinical settings. From the twelve studies, seven studies achieved high methodological quality scores. These studies were not only capable of assessing the type, quantity, and quality measures of functional activities, but could also distinguish healthy from non-healthy subjects and/or address disease severity levels. Conclusion: While many studies support ABT’s potential for telerehabilitation, few actually utilized it to assess mobility-related functional activities outside laboratory settings. To generate more appropriate outcome measures, there is a clear need to translate research findings and novel methods into practice

Techno‐economic assessment and comparison of different plastic recycling pathways: A German case study

Greenhouse gas (GHG) emissions need to be reduced to limit global warming. Plastic production requires carbon raw materials and energy that are associated today with predominantly fossil raw materials and fossil GHG emissions. Worldwide, the plastic demand is increasing annually by 4%. Recycling technologies can help save or reduce GHG emissions, but they require comparative assessment. Thus, we assess mechanical recycling, chemical recycling by means of pyrolysis and a consecutive, complementary combination of both concerning Global Warming Potential (GWP) [CO2e], Cumulative Energy Demand (CED) [MJ/kg], carbon efficiency [%], and product costs [€] in a process‐oriented approach and within defined system boundaries. The developed techno‐economic and environmental assessment approach is demonstrated in a case study on recycling of separately collected mixed lightweight packaging (LWP) waste in Germany. In the recycling paths, the bulk materials polypropylene (PP), polyethylene (PE), polyvinylchloride (PVC), and polystyrene (PS) are assessed. The combined mechanical and chemical recycling (pyrolysis) of LWP waste shows considerable saving potentials in GWP (0.48 kg CO2e/kg input), CED (13.32 MJ/kg input), and cost (0.14 €/kg input) and a 16% higher carbon efficiency compared to the baseline scenario with state‐of‐the‐art mechanical recycling in Germany. This leads to a combined recycling potential between 2.5 and 2.8 million metric tons/year that could keep between 0.8 and 2 million metric tons/year additionally in the (circular) economy instead of incinerating them. This would be sufficient to reach both EU and German recycling rate targets (EC 2018). This article met the requirements for a gold‐silver JIE data openness badge described at http://jie.click/badges

The (im?)possibility of a biological substrate for mental disorders

ACHTERGROND Er bestaat een tegenstelling tussen de ‘medische’ kijk op een psychiatrische aandoening (als gegevenheid van de natuur in de zin van een biologisch substraat) en de constructivistische visie. DOEL Onderzoeken hoe de constructivistische positie zich verhoudt tot deze medische kijk op psychiatrische aandoeningen. METHODE Een beschouwing gebaseerd op een conceptuele analyse, met name van het boek The social construction of what? (1999) van de Canadese wetenschapsfilosoof Ian Hacking. RESULTATEN Er blijken verschillende objecten van constructivistische analyses een rol te spelen bij psychiatrische aandoeningen, de aandoening zelf en het idee of concept van de aandoening. Deze verschillende objecten interacteren daarbij ook nog met elkaar. Deze interacties kunnen expliciet gemaakt worden door indifferente soorten te onderscheiden van interactieve soorten. Zo wordt duidelijk dat als een aandoening niet gedetermineerd wordt door een biologisch substraat, dit niet automatisch betekent dat zo’n aandoening geheel losstaat van een mensonafhankelijke natuur. CONCLUSIE Hackings filosofie biedt de mogelijkheid om voorbij te gaan aan de tegenstelling tussen de constructivistische positie en de medische kijk op psychiatrische ziekten. BACKGROUND: The constructivist position is often used for psychiatric diseases, in contrast with the general medical view. In the medical view a biological substrate is decisive for a classification as 'disease', which is not the case in the constructivist position. AIM: We investigate how both positions relate to each other in psychiatric diseases. METHOD: Analysis based on a conceptual analysis of Ian Hacking's book The Social Construction of What? (1999). RESULTS: Different objects ought to be distinguished in a constructivist analysis of psychiatric diseases; the disease itself and the idea or concept of that disease. These different objects interact with each other. These interactions can be made explicit by distinguishing interactive kinds from indifferent kinds. Doing so makes it clear that even if a disease is not determined by a biological substrate, this does not imply that a biological substrate is something completely separate from that disease. CONCLUSION: Hacking's philosophy makes it possible to move beyond the opposition between the medical and the constructivist account of psychiatric diseases by combining both accounts