1. Impact of metakaolin on mechanical performance of flax textile-reinforced cement-based compositesFilip Majstorović, Václav Sebera, Maruša Mrak, Sabina Dolenec, Marco Wolf, Laetitia Sarah Jennifer Marrot, 2022, izvirni znanstveni članek Povzetek: This study presents research on the effect of Portland cement (PC) replacement with metakaolin on the mechanical behavior of flax textile-reinforced cementitious matrices (TRCM). The composition of cementitious matrices and in-situ flax fibres was determined using X-ray diffraction and thermogravimetric analysis, while the reinforcement efficiency of the textile and mechanical behavior of TRCMs was investigated by three-point bending tests and finite element analysis. High amounts of PC replacement with metakaolin provided a calcium hydroxide-free environment, more suitable for the natural fibres, to avoid their degradation and embrittlement and, thus, significantly contribute to the ductility of the cement-based composite material.
Ključne besede: textile-reinforced concrete (TRC), flax textile, natural fibres, finite element, metakaolin, cement-based composites, open access
Objavljeno v DiRROS: 22.05.2023; Ogledov: 359; Prenosov: 169
 Celotno besedilo (8,40 MB)
Gradivo ima več datotek! Več... |
2. Environmental hazard of polypropylene microplastics from disposable medical masks : acute toxicity towards Daphnia magna and current knowledge on other polypropylene microplasticsAnita Jemec Kokalj, Andraž Dolar, Damjana Drobne, Marjan Marinšek, Matej Dolenec, Luka Škrlep, Gregor Strmljan, Branka Mušič, Andrijana Sever Škapin, 2022, izvirni znanstveni članek Povzetek: The COVID-19 pandemic has increased the use of disposable plastics, including medical masks, which have become a necessity in our daily lives. As these are often improperly disposed of, they represent an important potential source of microplastics in the environment. We prepared microplastics from polypropylene medical masks and characterised their size, shape, organic chemical leaching, and acute toxicity to the planktonic crustacean Daphnia magna. The three layers of the masks were separately milled and characterised. Each of the inner frontal, middle filtering, and outer layers yielded different types of microplastics: fibres were obtained from the inner and outer layer, but irregular fragments from the middle layer. The shape of the obtained microplastics differed from the initial fibrous structure of the intact medical mask layers, which indicates that the material is deformed during cryo-milling. The chemical compositions of plastics-associated chemicals also varied between the different layers. Typically, the inner layer contained more chemicals related to antimicrobial function and flavouring. The other two layers also contained antioxidants and their degradation products, plasticisers, cross-linking agents, antistatic agents, lubricants, and non-ionic surfactants. An acute study with D. magna showed that these microplastics do not cause immobility but do physically interact with the daphnids. Further long-term studies with these microplastics are needed using a suite of test organisms. Indeed, studies with other polypropylene microplastics have shown numerous adverse effects on other organisms at concentrations that have already been reported in the environment. Further efforts should be made to investigate the environmental hazards of polypropylene microplastics from medical masks and how to handle this new source of environmental burden.
Ključne besede: COVID-19 pandemic, plastics-associated chemicals, Daphnia magna, fibres, fragments, nanofibres, polypropylene microplastics, single-use plastic
Objavljeno v DiRROS: 05.05.2023; Ogledov: 335; Prenosov: 213
Celotno besedilo (3,28 MB)
Gradivo ima več datotek! Več... |
