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Ljubljana, Slovenia

Potocnik M.,FRI | Klemenc B.,FRI | Solina F.,FRI | Herlec U.,NTF
Geologija | Year: 2015

The methods used in geology to determine colour and colour coverage are expensive, time consuming, and/ or subjective. Estimates of colour coverage can only be approximate since they are based on rough comparisonbased measuring etalons and subjective estimation, which is dependent upon the skill and experience of the person performing the estimation. We present a method which accelerates, simplifies, and objectifies these tasks using a computer application. It automatically calibrates the colours of a digital photo, and enables the user to read colour values and coverage, even after returning from field work. Colour identification is based on the Munsell colour system. For the purposes of colour calibration we use the X-Rite ColorChecker Passport colour chart placed onto the photographed scene. Our computer application detects the ColorChecker colour chart, and finds a colour space transformation to calibrate the colour in the photo. The user can then use the application to read colours within selected points or regions of the photo. The results of the computerised colour calibration were compared to the reference values of the ColorChecker chart. The values slightly deviate from the exact values, but the deviation is around the limit of human capability for visual comparison. We have devised an experiment, which compares the precision of the computerised colour analysis and manual colour analysis performed on a variety of rock samples with the help of geology students using Munsell Rock-color Chart. The analysis showed that the precision of manual comparative identification on multicoloured samples is somewhat problematic, since the choice of representative colours and observation points for a certain part of a sample are subjective. The computer based method has the edge in verifiability and repeatability of the analysis since the application the original photo to be saved with colour calibration, and tagging of colouranalysed points and regions. © Author(s) 2015. Source


Ducman V.,Slovenian National Building And Civil Engineering Institute | Mirtic B.,NTF
Construction and Building Materials | Year: 2014

The water vapour permeability of concretes or various building systems is an important parameter when defining the concept of favourable living conditions. Within the scope of the research described in this paper, the water vapour permeability of concretes prepared with different lightweight aggregates (LWA) having an open porosity was compared with that of concretes made with a selected ordinary aggregate. It was found that the coefficient of water vapour permeability μ was, in the case of all the investigated concrete prepared by lightweight aggregates and used water/cement factors, less than 35, whereas in the case of the ordinary concrete it amounted to 84. It is interesting to note that SEM investigations of the interface (transition) zone between the aggregates and the cement matrix did not indicate the occurrence of any densification which could have a negative effect on the water vapour permeability of lightweight concretes (LWAC). © 2014 Elsevier Ltd. All rights reserved. Source


Ducman V.,ZAG Ljubljana | Korat L.,ZAG Ljubljana | Legat A.,ZAG Ljubljana | Mirtic B.,NTF
Materials Characterization | Year: 2013

In case of foamed lightweight aggregates (LWAs), porosity is introduced by the addition of a foaming agent to the glassy matrix, which degasses at an elevated temperature, so that the resulting gases remain trapped inside the glassy structure. The efficiency of action of MnO2 as a foaming agent in waste glass and waste glass/silica mud systems was studied. Samples were fired at different temperatures and with different dwelling times at a certain temperature, and the development of porosity was investigated by means of X-ray micro-tomography. It was found that, with the prolongation in dwelling times, the number of pores decreased, while, on the other hand, the volume of these pores increased, and that the addition of silica mud increases the foaming temperature and slows down the foaming process. © 2013 Elsevier Inc. Source


Malensek N.,NTF | Ducman V.,ZAG | Mirtic B.,NTF
Ceramics International | Year: 2015

Within the scope of the present study the cold-bonding process was used for the recycling of waste filter powder which was mixed with two different binders in different concentrations; alumino-silicate cement and potassium water glass, and combinations of these two materials, and hardened at room temperature. Selected samples were also fired at 1200 °C. Tests to determine tensile and compressive strength, density and porosity, as well as dilatometry and SEM analyses, were performed. As expected, compressive strength increased as a function of the concentration of the potassium water glass. When combinations of both binders were used, compressive strengths were higher, but a significant increase in strength was also achieved by firing the samples. The compressive strengths of the non-fired samples were in the range from 0.8 to 2.4 MPa, whereas after firing strengths of up to 36 MPa were obtained. During the firing density increased, and porosity was reduced, while the average pore size increased. The results of dilatometric analysis showed that the granulate produced with cement shrink upon firing up to 300 °C, but then start slowly to expand, whereas the granulate produced by water glass first expanded on firing up to 800 °C, and then began to shrink swiftly. In the case of combinations of the two binders, shrinkage as well as expansion on firing was less pronounced. Selected granulate prepared using potassium water glass were also tested in a refractory concrete matrix in order to verify their usability. © 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. Source


Korat L.,ZAG Ljubljana | Ducman V.,ZAG Ljubljana | Legat A.,ZAG Ljubljana | Mirtic B.,NTF
Ceramics International | Year: 2013

In the case of lightweight aggregate (LWA), porosity can be achieved by means of a high temperature foaming process. During this process a glassy matrix is created, and almost simultaneously the added foaming agent degasses and the resulting gasses remain trapped inside the glassy structure. The present paper deals with the foaming process which occurs in the case of silica sludge to which fly ash, which creates liquid phase, has been added, as well as SiC, which acts as a foaming agent. The development of porosity within the structure of this material was investigated at different temperatures and dwelling times by means of X-ray micro-tomography (micro-CT), and mercury intrusion porosimetry (MIP). The results were compared by means of both X-ray micro-tomography and mercury intrusion porosimetry, the first technique being applied within the pore size distribution range of between 50 μm to more than 1 mm, and the second within the range, between 0.0055 and 360 μm. Both techniques have certain limitations as well as certain advantages, but in the case of the investigated system micro-CT gives much more reliable results about porosity development over a prolonged firing time, at the selected temperature. The results showed that, at the selected temperature, which in this case amounted to 1220 °C, porosity as well as median pore size increased with increased dwelling times. In the case of prolonged dwelling times, the number of pores decreased, but, on the other hand, the volume of these pores increased. © 2013 Elsevier Ltd and Techna Group S.r.l. Source

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