Alkali activation of recycled ceramic aggregates from construction and demolition wastes

Environmental concerns are becoming increasingly more significant worldwide, thus creating the urgent need for new sustainable alternatives in the industrial sector. The present study assesses the fundamental properties of ceramic residue (CR) originated by demolition operations, specifically, the floor and wall tiles and sanitaryware furniture, for further incorporation in the construction sector, namely in alkali-activated bind- ers, mixed with other better-known precursors - fly ash (FA) and ladle furnace slag (LFS). Different CR/FA and CR/LFS weight ratios were considered and analyzed by mechanical behavior and microstructural analysis, which included uniaxial compression strength (UCS) tests, Scanning Electron Microscopy (SEM), X-ray Energy Dispersive Analyser (EDX), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Results obtained showed that the combination of CR and FA or LFS, activated with sodium silicate, produced UCS values higher than 20 MPa and 59 MPa, respectively, after 90 days curing.Activación alcalina de áridos cerámicos reciclados provenientes de residuos de construcción y demolición. Globalmente, las preocupaciones ambientales son cada vez más significativas, creando así la necesidad urgente de nuevas alternativas sostenibles en el sector industrial. El presente estudio evalúa las propiedades fundamentales de los residuos cerámicos (CR) provenientes de demolición, para ser reincorporados en el sector de la construcción, principalmente como ligantes activados alcalinamente, mezclados con otros precursores más conocidos: cenizas volantes (FA) y escorias de horno de cuchara (LFS). Se consideraron diferentes relaciones de peso CR/FA y CR/LFS, se analizó el comportamiento mecánico y se realizó un análisis microestructural, incluyendo pruebas de resistencia a la compresión (UCS), microscopía electrónica de barrido (SEM), análisis por energías dispersivas de rayos X (EDX), Rayos-X (XRD) y espectroscopía infrarroja por transformada de Fourier (FTIR). Los resultados mostraron que, a 90 días de curado, la combinación de CR y FA o LFS activada con silicato de sodio produjo valores de UCS superiores a 20 MPa y 59 MPa, respectivamenteFoundation for Science and Technology - FCT/MCTES (PIDDAC), within the framework of the R&D Project “JUSTREST - Development of Alkali Binders for Geotechnical Applications Made Exclusively from Industrial Waste”, reference PTDC/ECM-GEO/0637/2014. The author would also like to acknowledge the support of the Secretary of Higher Education, Figure 8. FTIR spectra of starting materials, the ladle furnace slag (LFS); ceramic residue (MCR) – milled for 32 hours; fly ash (FA), and 75CR-25FA/SH or SS mixtures (M1 and M2) and 75CR-25LFS/SH or SS mixtures (M3 and M4), after 90 days curing time. Science, Technology and Innovation, SENESCYT (Spanish acronym) from Ecuador, reference No. CZ03-000052-201

Sustainability assessment of half-sandwich panels based on alkali-activated ceramic/slag wastes cement versus conventional building solutions

This study assessed the sustainability of two partition walls and intended to contribute to the Circular Economy in the construction sector. A life cycle approach and a multi-criteria decision support method were applied to know the environmental, functional, and economic performances of the production process of half-sandwich panels based on alkali-activated ceramic/slag waste cement, choosing as system boundary the method “cradle to gate”. The proposed building solutions differ from each other in the type of insulating material used, either extruded polystyrene foam (APXPS) or expanded cork agglomerate board (APICB). Besides, a comparative analysis of the developed building solutions versus three reference constructive solutions: i) a conventional heavyweight partition wall, ii) a lightweight gypsum wall panel, and iii) a conceptual lightweight sandwich membrane building solution was performed. Results showed that the two proposed half-sandwich wall panels (APXPS and APICB) resulted in the most sustainable alternatives, of which the APXPS obtained the best overall results since it combined the best environmental, functional, and economic behavior. Besides, the environmental contribution analysis determined that the greatest environmental burden to the Global Warming Potential (GWP), in the case of the APXPS was associated with the XPS (57%), being the alkali activator (23%) placed as the second major contributor. When the ICB was used as the insulation layer, the energy used (nearly 38%) and the sodium silicate (about 17%) were the larger contributors to CO2 emissions. It is worth mentioning that the use of ICB represented a negative contribution (of about −34%) to the GWP category.This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/ 04029/2020, and the research project “CirMat: CIRcular aggregates for sustainable road and building MATerials”(ref. 16_Call#2)is funded by Iceland, Liechtenstein and Norway through the EEA Grants and Norway Grants, operationalized by the Portuguese Office of the Secretary of State for the Environment. RENEw, POCI-01-0247-FEDER-033834, that was co-funded by Fundo Europeu de Desenvolvimento Regional (FEDER), with Programa Operacional da Competitividade e Internacionalizaçao ˜ do Portugal 2020 (COMPETE 2020) The authors acknowledge the support of the DST group construction company for funding the project Chair DST/IB-S: Smart Systems for Construction

Nurses' perceptions of aids and obstacles to the provision of optimal end of life care in ICU

Contains fulltext : 172380.pdf (publisher's version ) (Open Access

Development of alkali activated ceramic residue and fly ash blends

Environmental concerns are becoming increasingly more significant worldwide, framing a scenario that points to the urgent development of new and sustainable alternatives for the industrial sector. The present study assesses the possible contribution of ceramic residue (CR) for alternative binders, for applications in the construction industry. The behavior of the CR alone in alkaline activated systems was initially tested, followed by a combination with a well-known precursor, fly ash (FA), considering different CR/FA weight ratios. Mechanical and microstructural analysis was conducted, including uniaxial compression strength (UCS) tests, Scanning Electron Microscopy (SEM), X-ray Energy Dispersive Analyzer (EDX), X-ray dif-fraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Results obtained showed that the most effective blend was a CR+FA combination, activated with sodium silicate, reach-ing UCS values higher than 20 MPa, after 90 days of ambient curing.(undefined

Effect of polyacrylonitrile fiber on the properties of alkali-activated ceramic/slag-based mortar

This study aims to optimize the mechanical behavior of alkali-activated mortar reinforced with polyacrylonitrile fibers. In order to accomplish this, ceramic waste from clay bricks and roof tiles was used as the primary pre- cursor, which was then combined with ladle furnace slag and activated with sodium silicate. Thereby, fibers were added to improve its brittle behavior, namely its toughness and the residual flexural strength of the material, thus enabling its use in a myriad of applications within the construction sector. So, an extensive experimental campaign was carried out to assess the influence of polyacrylonitrile fibers content (0%, 0.5%, and 1% in vol- ume) and the curing time (14, 28, and 90 days) on the main physical and mechanical properties, including capillarity, porosity, uniaxial compressive, and flexural strength. Microstructural analysis was accomplished with Scanning Electron Microscopy, X-ray Energy Dispersive Analyzer, X-ray diffraction, and Fourier Transform Infrared Spectroscopy. Experimental results of the developed mortars showed satisfactory mechanical properties, enhanced by the fibers, regardless of the fiber ratio added, attaining compressive and tensile under flexural strengths? values up to 47 MPa and 7 N/mm2, respectively, after 90 days of curing. Compared to non-reinforced mortars, these values represent an improvement of about 20% in both cases, thus justifying the addition of fibers.project “NextSea-Next generation monitoring of coastal systems in a scenario of global changes,” reference NORTE-01-0145-FEDER-000032, through funds from NORTE 2020 (Programa Operacional Regional do Norte) and FEDER (European Regional Development Fund), as well as from the Secretary of Higher Education, Science, Technology and Innovation, SENESCYT (Spanish acronym) from Ecuador, reference No. CZ03- 000052-2017, The authors would also like to acknowledge the contri bution of the company SGL Carbon Composites, SA, and “Ceramica ˆ Amaro Macedo” Company in Portugal for the supply of the poly acrylonitrile (PAN) fibers and the ceramic waste, respectiv

Axonal quantification of the white matter association fasciculi in cerebral hemispheres of cow (Bos taurus), pig (Sus scrofa domesticus) and rabbit (Oryctolagus cuniculus)

Cerebral white matter consists mainly of axons surrounded by myelin sheaths, which are grouped to form association, commissural, and projection fasciculi. The aim of our work was to quantify and compare under the microscope the axons of the white matter association fasciculi in the cerebral hemispheres of cow (Bos taurus), pig (Sus scrofa domesticus) and rabbit (Oryctolagus cuniculus) indirectly by identification of their myelin sheaths. The samples were taken from 30 cerebral hemispheres: 10 cow, 10 pig and 10 rabbit (15 right and 15 left). They were obtained following a protocol based on the Talairach-Tournoux coordinate system for human and primate brains. The slides were stained with Luxol Fast Blue, observed by optical microscopy, and photographed at 600x. Samples were also prepared for observation in scanning transmission electron microscopy (STEM) with osmium tetroxide. The myelin sheaths/axons were counted with the ImageJ software. Statistically significant differences in the number of myelin sheaths per 410 µm2 were found in the inferior and superior longitudinal fasciculi between the left and right hemispheres of cows, with predominance of the right hemisphere; and in the inferior occipitofrontal fasciculus of the rabbit with predominance of the left hemisphere. The use of animal models for experiments in the cerebral fasciculi, especially pig, could give us a greater understanding of the behavior of demyelinating and neurodegenerative diseases in humans

Fiber-reinforced alkali-activated cements from ceramic waste and ladle furnace slag without thermal curing

Alkaline-activated cement, as an alternative to conventional portland cement, is being increasingly studied due to its environmental advantages and engineering properties. However, research on the feasibility of using both uncommon precursors and curing at ambient temperature is still limited. This study aims to investigate the potential of ceramic wastes, specifically from brick and tile production and ladle furnace slag, as precursors in alkaline activated cement reinforced with polyacrylonitrile fibers cured at 20°C. Sodium silicate, in solution form, was used to activate the precursors, and three different fiber contents were tested, namely 0%, 0.5%, and 1%, by volume. Physical properties, such as capillarity and porosity, were assessed. Moreover, the mechanical behavior was thoroughly characterized by uniaxial compressive, flexural, and elasticity modulus tests. In addition, a thorough microstructural characterization, including scanning electron microscopy, X-ray energy dispersive analyzer, X-ray diffraction, and Fourier transform infrared spectroscopy was conducted at 14, 28, and 90 days. The results revealed that environmentally friendly alkali-activated binders were produced from wastes with limited industrial recycling possibilities. The mixture with 0.5% fibers was the one that presented better results, i.e., a flexural strength of 8.84  N/mm2 and compressive strength of ∼29  MPa at 90 days. The mechanical performance of this material is relevant, especially considering that a relatively low curing temperature was applied. The results also showed that calcium aluminum silicate hydrate (C-A-S-H) was detected as the main reaction product.This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020, and the research project CirMat: CIRcular aggregates for sustainable road and building MATerials (ref. 16_Call#2) is funded by Iceland, Liechtenstein and Norway through the EEA Grants and Norway Grants, operationalized by the Portuguese Office of the Secretary of State for the Environment; as well as RENEw, POCI-01-0247-FEDER-033834, that was co-funded by Fundo Europeu de Desenvolvimento Regional (FEDER), with Programa Operacional da Competitividade e Internacionalização do Portugal 2020, COMPETE 2020. The authors acknowledge the support of the DST Group construction company for funding the project Chair dst/IB-S: Smart Systems for Construction. The Secretary of Higher Education, Science, Technology and Innovation, SENESCYT (Spanish acronym) from Ecuador, as well as the contribution of SGL Carbon Composites S.A, Cerâmica Amaro Macedo, and Megasa in Portugal for the supply of the PAN fibers, the ceramic bricks waste, and the ladle furnace slag, respectively

A methodological framework for capturing marine small-scale fisheries' contributions to the sustainable development goals

International audienc