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Iskalni niz: "ključne besede" (durability) .

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RILEM TC 247-DTA round robin test : mix design and reproducibility of compressive strength of alkaliactivated concretes
John L. Provis, Kamel Arbi, Susana Bernal, Dali Bondar, Anja Buchwald, Arnaud Castel, Sundararaman Chithiraputhiran, Martin Cyr, Alireza Dehghan, Katja Dombrowski-Daube, Ashish Dubey, Vilma Ducman, Gregor J. G. Gluth, Sreejith Nanukuttan, Karl Peterson, Francisca Puertas, Arie van Riessen, Manuel Torres-Carrasco, Guang Ye, Yibing Zuo, 2019, izvirni znanstveni članek

Povzetek: The aim of RILEM TC 247-DTA Durability Testing of Alkali-Activated Materials is to identify and validate methodologies for testing the durability of alkali-activated concretes. To underpin the durability testing work of this committee, five alkali-activated concrete mixes were developed based on blast furnace slag, fly ash, and flash-calcined metakaolin. The concretes were designed with different intended performance levels, aiming to assess the capability of test methods to discriminate between concretes on this basis. A total of fifteen laboratories worldwide participated in this round robin test programme, where all concretes were produced with the same mix designs, from single-source aluminosilicate precursors and locally available aggregates. This paper reports the mix designs tested, and the compressive strength results obtained, including critical insight into reasons for the observed variability in strength within and between laboratories.
Ključne besede: alkali-activated materials (AAM), mechanical properties, test method, Rilem TC, durability
Objavljeno v DiRROS: 14.09.2023; Ogledov: 109; Prenosov: 74
.pdf Celotno besedilo (431,19 KB)
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RILEM TC 247-DTA round robin test : carbonation and chloride penetration testing of alkali-activated concretes
Gregor J. G. Gluth, Kamel Arbi, Susana Bernal, Dali Bondar, Arnaud Castel, Sundararaman Chithiraputhiran, Alireza Dehghan, Katja Dombrowski-Daube, Ashish Dubey, Vilma Ducman, Karl Peterson, Penny Pipilikaki, Siska L. A. Valcke, Guang Ye, Yibing Zuo, John L. Provis, 2020, izvirni znanstveni članek

Povzetek: Many standardised durability testing methods have been developed for Portland cement-based concretes, but require validation to determine whether they are also applicable to alkali-activated materials. To address this question, RILEM TC 247-DTA "Durability Testing of Alkali-Activated Materials" carried out round robin testing of carbonation and chloride penetration test methods, applied to five different alkali-activated concretes based on fly ash, blast furnace slag or metakaolin. The methods appeared overall to demonstrate an intrinsic precision comparable to their precision when applied to conventional concretes. The ranking of test outcomes for pairs of concretes of similar binder chemistry was satisfactory, but rankings were not always reliable when comparing alkali-activated concretes based on different precursors. Accelerated carbonation testing gave similar results for fly ash-based and blast furnace slag-based alkali-activated concretes, whereas natural carbonation testing did not. Carbonation of concrete specimens was observed to have occurred already during curing, which has implications for extrapolation of carbonation testing results to longer service life periods. Accelerated chloride penetration testing according to NT BUILD 443 ranked the tested concretes consistently, while this was not the case for the rapid chloride migration test. Both of these chloride penetration testing methods exhibited comparatively low precision when applied to blast furnace slag-based concretes which are more resistant to chloride ingress than the other materials tested.
Ključne besede: alkali-activated materials (AAM), carbonatization, chloride penetration, Rilem TC, durability
Objavljeno v DiRROS: 17.08.2023; Ogledov: 129; Prenosov: 95
.pdf Celotno besedilo (1014,30 KB)
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Environmentally friendly protection of European beech against fire and fungal decay using a combination of thermal modification and mineralisation
Rožle Repič, Andreja Pondelak, Davor Kržišnik, Miha Humar, Nataša Knez, Friderik Knez, Andrijana Sever Škapin, 2023, izvirni znanstveni članek

Povzetek: The demand for construction timber is continuously increasing, due to its favourable characteristics. However, the adequate protection of wood is key to its successful use, as it is flammable and susceptible to biodegradation. Given that thermal modification enhances the durability of wood, and mineralisation with CaCO3 considerably improves its fire properties, it is worth considering the combined effects of the two methods. European beech (Fagus sylvatica) was selected to determine the effects of a) thermal modification, b) mineralisation through the in-situ formation of CaCO3, and c) a combination of the two procedures, on resistance to decay fungi, reaction to fire and the mechanical properties of the wood. Microscopic analysis and comparisons of the samples before and after exposure to fungi were also conducted. Mineralised wood generally had a slightly alkaline pH value and higher equilibrium moisture content, while thermal modification lowered the equilibrium moisture content. The present study demonstrated the combined effect of thermal modification and mineralisation: the best response to fire as well as resistance to fungi was achieved when the two treatments were combined. Results from the Brinell hardness and three-point bending tests indicate that both modification procedures can slightly impair the mechanical properties of the wood.
Ključne besede: wood, protection, durability, mechanical properties
Objavljeno v DiRROS: 12.07.2023; Ogledov: 166; Prenosov: 110
.pdf Celotno besedilo (3,26 MB)
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Experimental carbonation study for a durability assessment of novel cementitious materials
Lucija Hanžič, Sebastijan Robič, Alisa Machner, Marie Helene Bjørndal, Klaartje De Weerdt, Yushan Gu, Benoit Bary, Rosa Maria Lample Carreras, Aljoša Šajna, 2021, izvirni znanstveni članek

Povzetek: Durability predictions of concrete structures are derived from experience-based require- ments and descriptive exposure classes. To support durability predictions, a numerical model related to the carbonation resistance of concrete was developed. The model couples the rate of carbonation with the drying rate. This paper presents the accelerated carbonation and moisture transport exper- iments performed to calibrate and verify the numerical model. They were conducted on mortars with a water-cement ratio of either 0.6 or 0.5, incorporating either a novel cement CEM II/C (S-LL) (EnM group) or commercially available CEM II/A-S cement (RefM group). The carbonation rate was determined by visual assessment and thermogravimetric analysis (TGA). Moisture transport experi- ments, consisting of drying and resaturation, utilized the gravimetric method. Higher carbonation rates expressed in mm/day−0.5 were found in the EnM group than in the RefM group. However, the TGA showed that the initial portlandite (CH) content was lower in the EnM than in the RefM, which could explain the difference in carbonation rates. The resaturation experiments indicate an increase in the suction porosity in the carbonated specimens compared to the non-carbonated specimens. The study concludes that low clinker content causes lower resistance to carbonation, since less CH is available in the surface layers; thus, the carbonation front progresses more rapidly towards the core.
Ključne besede: mortar, absorption of water, carbonation, durability assessment, model verification
Objavljeno v DiRROS: 05.07.2023; Ogledov: 160; Prenosov: 109
.pdf Celotno besedilo (4,84 MB)
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Combining mineralisation and thermal modification to improve the fungal durability of selected wood species
Rožle Repič, Andreja Pondelak, Davor Kržišnik, Miha Humar, Andrijana Sever Škapin, 2022, izvirni znanstveni članek

Povzetek: The development of non-biocidal and environmentally friendly systems to protect wood against biological decay has become a high priority in recent years. In the present study the impact of an innovative modification procedure, combining two environmentally friendly modification methods: thermal modification and mineralisation, using an aqueous solution of calcium acetoacetate as a precursor, on the fungal durability of wood was evaluated. European beechwood (Fagus sylvatica) and Norway sprucewood (Picea abies) were selected as model wood species. Wood samples were treated using either a single or combination of both methods and exposed to four different fungi: Gloeophyllum trabeum, Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus. The effect of the different modifications on moisture content, dynamic vapour sorption, contact angle and pH value was also evaluated. Overall, the highest durability against Rhodonia placenta, Trametes versicolor and Pleurotus ostreatus was achieved through thermal modification in both wood species, while the combination of mineralisation and thermal modification has a synergistic effect against degradation by Gloeophyllum trabeum. In the case of beechwood the mass loss decreased from 41% for native to 6% for combined modified samples. We proved that the effectiveness of different treatment against fungal decay of wood were in strong dependence of their moisture content, dynamic vapour sorption, contact angle and pH values. The role of fungi on the morphology of the wood and on crystal structure of formed carbonate was investigated using SEM-EDS analysis.
Ključne besede: thermal modification, wood mineralization, fungal durability, environmentally friendly modification methods
Objavljeno v DiRROS: 20.06.2023; Ogledov: 186; Prenosov: 192
.pdf Celotno besedilo (3,55 MB)
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