Specimens of sensitized type AISI 304 stainless steel were subjected to constant load and exposed to an aqueous sodium thiosulphate solution. Intergranular stress-corrosion cracking was monitored simultaneously for electrochemical noise, acoustic emission, and specimen elongation. A section of the gauge length was monitored optically with subsequent analysis by digital image correlation. Correlations between the results were observed and analysed. Electrochemical noise and elongation are associated with crack propagation from the early stages, whereas acoustic emission is associated with the final stages of fracture. Digital image correlation analysis is sensitive to crack development, and is used to measure crack length and crack openings.
COBISS.SI-ID: 1618535
The response of autoclaved aerated concrete (AAC) confined masonry buildings to seismic ground motion has been studied. Two two-story and on three-story models have been tested on a uni-directional shaking table. Although they were different in height and type of floor structures, the behavior of all models was siilar. Typical storey mechanism, characterised by diagonal shear failure mode of walls in the ground floor in the direction of excitation has been observed in all cases. Taking into consideration the observed behaviour, a numerical model with concentrated masses and storey hysteretic rules has been used to simulate the observed behaviour. Good agreement between the experimentally observed and calculated non-linear behaviour has been obtained.
COBISS.SI-ID: 1837927
In the study characterization of steel corrosion in concrete at the macro- andmicro-level was performed. Physical (electrical-resistance probes) and electrochemical techniques (coupled multi-electrode arrays) were implemented in order to upgrade the general information that conventional electrochemical techniques can provide. Measurements were performed in mortar exposed to periodic wetting and drying. Steel corrosion damage was assessed by micro X-ray computer tomography (CT) and SEM. The results were compared and interpreted. By combined use of Micro-CT and electrochemical methods, new insights into the corrosion mechanisms of steel in concrete were obtained.
COBISS.SI-ID: 1966695
Carbon steel slag is quite commonly used in road construction to replace natural aggregate. Since it is important to evaluate such a replacement from the environmental point of view, a Life Cycle Assessment was carried out in order to compare the environmental impacts of the construction of asphalt wearing courses with the use of siliceous aggregates (the "conventional scenario"), and the use of alternative, steel slag aggregates (the "alternative scenario"). The main advantage of the alternative scenario is that a reduction can be achieved in the consumption of natural aggregate, as well as in the quantity of slag deposited on landfill sites. On the other handlarger amount of bitumen is needed as a binder. However, the results of the Life Cycle Assessment (based on consequential modelling) revealed that thealternative scenario is to be significantly preferred if the following impact categories are taken into account: Acidification, Eutrophication, Photochemical Ozone Creation and Human Toxicity. In the case of the discussed indicators, the impacts are reduced to a level equal to about 80 % of the conventional scenario impacts. This benefit was additionally evaluated by means of a transport sensitivity analysis, which provided results which could be useful for road managers working on case studies using similar constructionmaterials. The alternative scenario is more sustainable than the conventional scenario with regard to the discussed impact categories even whentaking into account long delivery distances of the steel slag aggregate (Ž100 km) and minimal delivery distances of the siliceous aggregate. Considering similar delivery distances in both scenarios, the alternative scenario was found to be beneficial also with regard to the Global Warming, but only when the delivery distance of the steel slag aggregates did not exceed 160 km.
COBISS.SI-ID: 2069863
In the present work compact and ground cement composites in which 30% of cement by mass was replaced by ladle slag were investigated for their chemical and physico-mechanical properties. To evaluate long term environmental impacts, leachability test based on diffusion, which combined both, diffusion and dissolution of contaminants, was performed in water and saline water. Total element concentrations and Cr(VI) were determined in leachates over a time period of 180 days. At the end of the experiment, the mineralogical composition and the physico mechanical stability of cement composites was also assessed. The results revealed that Cr(III) and Cr(VI) were immobilized by the hydration products formed in the cement composites with the addition of ladle slag. Cr(VI) content originating from the cement was also appreciably reduced by Fe(II) from minerals present in the added ladle slag, which thus had significant positive environmental effects. Among metals, only Mo and Ba were leached in elevated concentrations, but solely in ground cement composites with the addition of ladle slag. It was demonstrated that the presence of ladle slag in cement composites can even contribute to improved mortar resistance. The investigated ladle slag can be successfully implemented in cement composites as supplementary cementitious material.
COBISS.SI-ID: 28586535
Copper corrosion has been studied in simulated groundwater with and without added bentonite clay using different electrochemical techniques. The corroded surfaces were characterized by SEM/EDS, Raman spectroscopy and Auger depth profiling. In both environments small amounts of sulphide (0.005 mM) control the early corrosion behaviour. Under aerated conditions an initially formed Cu2S film is rapidly converted to a non-protective layer of cuprite and corrosion proceeds with the deposition of an outer layer of atacamite. In the presence of bentonite corrosion proceeds slowly under O2 transport control. Noatacamite is observed and the Cu surface appears slightly pitted.
COBISS.SI-ID: 2071655
The efficiency of strengthening traditionally built three-leaf stone masonry walls with different types of composite reinforced coating has been investigated. Glass fibre grid in single component fibre reinforced mortar andglass fibre fabric in epoxy resin matrix were used as coating materials. Four different coating types have been applied, with coating placed on one or both sides of the walls, anchored or not anchored to the masonry at the corners of the walls. Ten walls have been tested by subjecting them to cyclic shear loading at constant precompression, among them two walls in the originalstate as the control specimens. Four walls have been first tested up to the occurrence of the first significant damage, strengthened and then re-tested up to collapse, whereas four walls have been strengthened undamaged and tested up to collapse. All walls failed in shear. Significant increase in lateral resistance with regard to control walls was observed in all cases, up to 2.5-4.0-times the resistance of the control walls. The degree of improvement did not depend on the type of coating but on the technology of application. Although the coating increased the rigidity of the walls, displacement and energy dissipation capacities have been also improved.
COBISS.SI-ID: 2073703
Pool fires of light fuel oil (LFO) in above-ground storages with steel-aluminium containers are discussed. A model is developed for assessmentsof risks of between-tank fire spread. Radiative effects of the flame body are accounted for by a solid flame radiation model. Thermal profiles evolved due to fire in the adjacent tanks and the their consequentialstructural response is pursued in an exact (materially and geometrically non-linear) manner. The model's derivation is demonstrated on the LFO tank storage located near the Port of Koper (Slovenia). In support of the model, data from literature are adopted where appropriate. Analytical expressions are derived correspondingly for calculations of emissive characteristics of LFO pool fires. Additional data are collected from experiments. Fire experiments conducted on 300cm diameter LFO pans and at different wind speeds and high-temperature uniaxial tension tests of the analysed aluminium alloys types 3xxx and 6xxx are presented. The model is of an immediate fire engineering practical value (risk analyses) or can be used for further research purposes (e.g. sensitivity and parametric studies). The latter use is demonstrated in the final part of the paper discussing possible effects of high-temperature creep of 3xxx aluminium.
COBISS.SI-ID: 2163047
The implementation of repair works on concrete structures is on the increase since many existing concrete buildings have been exposed for long periods of time to different climates, as well as to other severe conditions, and have consequently deteriorated. Repair mortars need to fulfil the requirements of the EN 1504 series before being used in practice. Different mixtures, based on three different precursors (fly ash, ground granulated blast furnace slag, and metakaolin) and processed by alkali activated technology, have been assessed with regard to their suitability for the repair of concrete. Whereas the slag-based repair mortar delaminated from the substrate, and was thus unsuitable for its intended use, the other two mortars which were based on the precursors fly ash and metakaolin exhibited good mechanical properties and good adhesion. The bond strength of the metakaolin and fly ash mortars ranged from 1.8 to 2.3 N/mm2, and thus met these criteria for both structural and non-structural repair mortars. The capillary absorption of all three mixtures was too high to fulfil the criteria of EN 1504-3 for structural repair products, but the fly ash and metakaolin mixtures still have the potential to be used for non-structural repair works. The problem of efflorescence in all three mixtures was also assessed.
COBISS.SI-ID: 2231911
Photocatalytic TiO2 degrades organic matter unselectively. However, in certain applications, such as degradation of pollutants, selectivity towards pollutants is beneficial. We synthesized core@shell TiO2@SiO2 nanoparticles with photocatalytic activity featuring a significantly faster preferential degradation of model pollutant (rhodamine B) in presence of abundant concentration of natural organic matter compared to pure TiO2 (P25). The material%s photocatalytic activity was tested in aqueous medium. The selectivity of prepared effect of core@shell materials is explained based on transmission electron microscopy, nitrogen adsorption, X-ray powder diffraction and zeta potential measurements.
COBISS.SI-ID: 2268519