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Povzetek: Construction and demolition waste produced in the Republic of North Macedonia remains a major economic and environmental problem because all construction and demolition waste ends up in local dumps or is disposed of in a landfill. The objective of this study was to investigate the influence of the process parameters on the physical and mechanical properties of clay-based ceramics with partial replacement of clay with construction and demolition waste. Determination of the chemical composition of the waste demolition brick using X-ray fluorescence showed that it consisted of different oxides such as SiO2, Al2O3, Fe2O3 and CaO and minor contents of alkaline and earth alkaline oxides. Production of these ceramics was conducted through the consolidation of clay and waste demolition brick with the evaluation of the main process parameters such as sintering temperature [ST], the content of waste demolition brick [WDB] and isothermal period at the final temperature [IP]. The final model equations for density and bending strength dependence of the main process parameters were obtained and presented. The microstructure of the ceramics determined by SEM shows that the waste material is homogeneously dispersed in the clay matrix.
Ključne besede: CDW, clay, ceramics, properties
Objavljeno v DiRROS: 19.08.2024; Ogledov: 472; Prenosov: 181
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Povzetek: Namen prispevka temelji na inovativnem postopku izdelave nanokompozitov na osnovi poli(3-hidroksibutirata) (PHB) in nanofibrilirane celuloze (NFC). Raziskovalno delo obravnava pripravo koncentratnih mešanic PHB-prahu in NFC v vodni raztopini za tehnologijo ekstruzijskega mešanja. Ekstrudat koncentrirane mešanice PHB/NFC je bil nato uporabljen kot dodatek h granulirani obliki PHB pri pripravi brizganih vzorcev z različnimi utežnimi deleži NFC. V prispevku so podane določene omejitve pri predelavi tovrstnih materialov in predlagane uporabne rešitve za njihovo optimiziranje. Morfološke lastnosti nanokompozitnih komponent smo raziskali z elektronsko mikroskopijo (FE-SEM), mehanske lastnosti pa z nateznim preizkusom. Morfološka preiskava koncentratnih mešanic je razkrila prepleteno sestavo celuloznih nanofibril in polimernih kroglic, pri čemer se posamezne fibrile prepletajo v obliki širših pramenov in ustvarjajo videz zamrežene strukture znotraj polimerne komponente. Mikroskopski posnetki nanokompozitnih mešanic in izboljšane mehanske lastnosti izhodnih materialov potrjujejo,da je adhezivni stik med matrično in ojačitveno komponento dosežen, porazdelitev celuloznih nanofibril po polimerni osnovi pahomogena. Nanokompoziti z visokimi utežnimi deleži NFC (10 % utežnega deleža) dosegajo pomembno večje vrednosti modula elastičnosti (Et = 1720 MPa) in raztezka pri pretrgu (b = 3,1 %) ter prenesejo višje pretržne napetosti ( M = 26 MPa) v primerjavi z referenčnim polimernim vzorcem (Et = 1340 MPa;b = 2,4 %; M = 20 MPa). Rezultati študije dokazujejo, da je ob pravilni predpripravi polimernih mešanic in optimizaciji tehnologije ekstruzijske predelave, mogoče izdelati trdne in žilave materiale, pri čemer delež ojačitvene faze narekuje stopnjo izboljšave končnih lastnosti biopolimerne osnove.
Ključne besede: nanofibrilirana celuloza, poli(3-hidroksibutirat), morfologija, mehanske lastnosti, ekstruzija, tehnologija brizganja
Objavljeno v DiRROS: 14.08.2024; Ogledov: 420; Prenosov: 207
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Povzetek: Increasing use of the ground as a thermal reservoir is expected in the near future. Shallow geothermal energy (SGE) systems have proved to be sustainable alternative solutions for buildings and infrastructure conditioning in many areas across the globe in the past decades. Recently novel solutions, including energy geostructures, where SGE systems are coupled with foundation heat exchangers, have also been developed. The performance of these systems is dependent on a series of factors, among which the thermal properties of the soil play a major role. The purpose of this paper is to present, in an integrated manner, the main methods and procedures to assess ground thermal properties for SGE systems and to carry out a critical review of the methods. In particular, laboratory testing through either steady-state or transient methods are discussed and a new synthesis comparing results for different techniques is presented. In situ testing including all variations of the thermal response test is presented in detail, including a first comparison between new and traditional approaches. The issue of different scales between laboratory and in situ measurements is then analysed in detail. Finally, the thermo-hydro-mechanical behaviour of soil is introduced and discussed. These coupled processes are important for confirming the structural integrity of energy geostructures, but routine methods for parameter determination are still lacking.
Ključne besede: hallow geotehermal systems, soil thermal behaviour, laboratory testing, in situ testing, thermo-mechanical behaviour
Objavljeno v DiRROS: 14.08.2024; Ogledov: 380; Prenosov: 242
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Povzetek: The use of geotextile filters has been a common application in geo-environmental and geotechnical engineering for decades. The purpose of the present paper is to assess the influence of artificial physical clogging and cyclic water flow on the water permeability characteristics of nonwoven geotextiles used commonly in filter and drainage systems. Despite many studies examining the behavior of soil-geosynthetics, the mechanism of physical clogging is not fully understood yet and remains incompletely defined. Artificial clogging and cyclic water flow tests have been conducted according to a procedure created by the authors. Three nonwoven geotextiles and silty sand were employed in the test series. Hydraulic properties of the tested geosynthetics were determined according to the ISO standard. Filter design criteria are also discussed. The paper also presents the changes of water permeability characteristics due to clogging and cyclic water flow. The results show significant decrease of water permeability coefficients of the tested nonwoven geotextiles after artificial clogging and under cyclic water flow. Furthermore, the clogging mechanism was observed and confirmed by three-dimensional computed tomography.
Ključne besede: nonwoven geotextile, clogging, cyclic flow, permeability, soil
Objavljeno v DiRROS: 14.08.2024; Ogledov: 348; Prenosov: 210
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Povzetek: Aggregates made from fly ash have been developed by means of the cold-bonding process, with the addition of Portland cement as a binder at (10, 20, and 30) % of mass fractions, and by pouring the mixtures into moulds. After curing for 28 d the samples were processed into aggregate by crushing and sieving. An aggregate containing a weight percentage of 10 % of cement was additionally produced by pelletization on a granulating plate. The density, water-adsorption capacity, porosity, compressive strengths, and frost resistance of the samples were determined. The aggregates prepared by both routes were then used to make concrete samples, whose properties were then compared to those of conventional concrete made using limestone aggregate. The compressive strength of the concrete made with the granulated aggregate reached 16.0 MPa after 28 d, whereas that of the concrete made with crushed aggregate amounted to 24.1 MPa, and that of the conventional concrete was 34.6 MPa.
Ključne besede: fly ash, lightweight aggregates, density, compressive strength, frost resistance
Objavljeno v DiRROS: 14.08.2024; Ogledov: 387; Prenosov: 274
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