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Abstract: Alkali-activated foams (AAFs) present one of the most promising materials for use in the construction sector. Their main advantages lie in their utilization of waste material and their ability to form at temperatures well below 100 °C, while still competing in performance with foamed glass or ceramics. The present body of research has focused on improving the thermal stability of fly-ash foams by i) adding metakaolin, and ii) changing the activator from sodium-based to potassium-based components. It has been confirmed that a certain increase in thermal resistance is achieved through the addition of metakaolin while changing activators played a crucial role. While sodium-based AAFs without metakaolin start to shrink at approximately 600 °C, samples that have had metakaolin added start to shrink at approximately 700 °C. Samples without metakaolin that have used a potassium activator start to shrink at approximately 800 °C, whereas potassium-based samples with the addition of metakaolin start to shrink at approximately 900 °C.
Keywords: alkali activated materials, geopolymers, high temperature, resistance, foams
Published in DiRROS: 01.08.2023; Views: 250; Downloads: 192
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Abstract: Alkali-activated composites of lightweight aggregates (LWAs, with beneficial insulating properties) and alkali-activated foams (AAFs, higher added value products due to their production from waste materials at well below 100 ◦C) allow for the expectation of superior properties if a chemical bonding reaction or mechanical interlocking occurs during production. However, the interfaces between LWAs and an AAF have not been studied in detail so far. Chemical reactions are possible if the LWA contains an amorphous phase which can react with the alkaline activators of the AAF, increase the bonding, and thus, also their mechanical strengths. These, in turn, allow for an improvement of the thermal insulation properties as they enable a further density reduction by incorporating low density aggregates. This work features a first-detailed analyses of the interfaces between the LWAs’ expanded polystyrene, perlite, expanded clay and expanded glass, and the alkali-activated foam matrices produced using industrial slags and fly ash. Some are additionally reinforced by fibers. The goal of these materials is to replace cement by alkali-activated waste as it significantly lowers the environmental impact of the produced building components.
Keywords: alkali activated materials/geopolymers, light weight aggregates, SEM
Published in DiRROS: 20.06.2023; Views: 345; Downloads: 177
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Abstract: In this study we compare the leaching behavior and the antibacterial and cytotoxic properties of 100% slag or stone wool derived alkali activated materials. The antibacterial activity was measured as the inhibiting capacity against two Gram- negative bacterial strains, Escherichia coli and Pseudomonas aeruginosa and one Gram-positive bacterial strain: Enterococcus faecalis. The cytotoxicity properties were tested on mouse embryonic fibroblast NIH-3T3 cell-line. It was proved that the high quality of the 3D aluminosilicate network of the consolidated materials obtained from powders of CaO or MgO-rich slags or stone wool, opportunely activated with NaO and/or Na-silicate, was capable of stabilizing heavy metal cations. The concentrations of leachate heavy cations were lower than the European law limit when tested in water. The effect of additives in the composites, basal fibers or nanocellulose, did not reduce the chemical stability and slightly influenced the compressive strength. Weight loss in water increased by 20% with basalt fibers addition, while it remained almost constant when nanocellulose was added. All the consolidated materials, cement-like in appearance, exhibited limited antibacterial properties (viability from 50 to 80% depending on the bacterial colony and the amount of sample) and absence of cytotoxicity, envisaging good acceptance from part of the final consumer and zero ecological impact. CaO-rich formulations can replace ordinary Portland cement (showing bacterial viability at 100%) with a certain capability for preventing the reproduction of the E. coli and S. aureus bacteria with health and environmental protection results.
Keywords: antibacterial properties, cytotoxicity, alkali-activated materials, slag, stone wool, waste utilization, social acceptance
Published in DiRROS: 22.05.2023; Views: 308; Downloads: 171
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Abstract: Background: In agroecosystems, viruses are well known to influence crop health and some cause phytosanitary and economic problems, but their diversity in non-crop plants and role outside the disease perspective is less known. Extensive virome explorations that include both crop and diverse weed plants are therefore needed to better understand roles of viruses in agroecosystems. Such unbiased exploration is available through viromics, which could generate biological and ecological insights from immense high-throughput sequencing (HTS) data. Results: Here, we implemented HTS-based viromics to explore viral diversity in tomatoes and weeds in farming areas at a nation-wide scale. We detected 125 viruses, including 79 novel species, wherein 65 were found exclusively in weeds. This spanned 21 higher-level plant virus taxa dominated by Potyviridae, Rhabdoviridae, and Tombusviridae, and four non-plant virus families. We detected viruses of non-plant hosts and viroid-like sequences and demonstrated infectivity of a novel tobamovirus in plants of Solanaceae family. Diversities of predominant tomato viruses were variable, in some cases, comparable to that of global isolates of the same species. We phylogenetically classified novel viruses and showed links between a subgroup of phylogenetically related rhabdoviruses to their taxonomically related host plants. Ten classified viruses detected in tomatoes were also detected in weeds, which might indicate possible role of weeds as their reservoirs and that these viruses could be exchanged between the two compartments. Conclusions: We showed that even in relatively well studied agroecosystems, such as tomato farms, a large part of very diverse plant viromes can still be unknown and is mostly present in understudied non-crop plants. The overlapping presence of viruses in tomatoes and weeds implicate possible presence of virus reservoir and possible exchange between the weed and crop compartments, which may influence weed management decisions. The observed variability and widespread presence of predominant tomato viruses and the infectivity of a novel tobamovirus in solanaceous plants, provided foundation for further investigation of virus disease dynamics and their effect on tomato health. The extensive insights we generated from such in-depth agroecosystem virome exploration will be valuable in anticipating possible emergences of plant virus diseases and would serve as baseline for further post-discovery characterization studies.
Keywords: tomato, weed, virus, viroid, virome, virus discovery, virus diversity, phylogenetics, metagenomics, viromics
Published in DiRROS: 13.04.2023; Views: 579; Downloads: 126
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Abstract: Early detection is important for the management of invasive alien species. In the last decade citizen science has become an important source of such data. Here, we used opportunistic records from the “LIFE ARTEMIS” citizen science project, in which people submitted records from places where they observed tree pests, to understand the distribution of a rapidly-spreading forest pest: the oak lace bug (Corythucha arcuata) in Slovenia. These citizen science records were not distributed randomly. We constructed a species distribution model for C. arcuata that accounted for the biased distribution of citizen science by using the records of other tree pests and diseases from the same project as pseudo-absences (so-called constrained pseudo-absences), and compared this to a model with pseudo-absences selected randomly from across Slovenia. We found that the constrained pseudo-absence model showed that C. arcuata was more likely to be found in east, in places with more oak trees and at lower elevations, and also closer to highways and railways, indicating introduction and dispersal by accidental human transport. The outputs from the model with random pseudo-absences were broadly similar, although estimates from this model tended to be higher and less precise, and some factors that were significant (proximity to minor roads and human settlements) were artefacts of recorder bias, showing the importance of taking the distribution of recording into account wherever possible. The finding that C. arcuata is more likely to be found near highways allows us to design advice for where future citizen science should be directed for efficient early detection.
Keywords: Oak lace bug, ecological modelling, citizen science, invasive alien species, early detection, Corythucha arcuata
Published in DiRROS: 08.09.2022; Views: 494; Downloads: 248
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