V prispevku smo s pomočjo sistema za avtomatizirano vrednotenje zlepljenosti (ABES) ugotavljali razvoj strižne trdnosti ribjega kleja pri lepljenju lesa. Uporabili smo bukov (Fagus sylvatica L.) ...furnir, ki smo ga lepili pri konstantnem tlaku 12 barov, medtem ko smo spreminjali temperaturo in čas stiskanja. Temperatura je znašala med 25 °C in 100 °C, z intervalom 25 °C, čas stiskanja pa od 1 minute do 60 minut. Dosežena maksimalna strižna trdnost je znašala okoli 10 N/mm2, dosegli smo jo pri vseh štirih proučevanih temperaturah stiskanja. Na podlagi rezultatov študije smo ugotovili, da strižna trdnost ribjega kleja pri različnih temperaturah segrevanja neenakomerno narašča. Pri višjih temperaturah segrevanja hitreje dosežemo maksimalne strižne trdnosti. Strižne trdnosti spoja lepila iz ribjega kleja smo ugotavljali tudi po standardih EN 204 in EN 205.
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•The mechanisms of calcium acetoacetate transformations into CaCO3 was proposed.•Strong influence of relative humidity on CaCO3 polymorph formation has been shown.•The formed crystal ...structure is found to be vaterite.•The amorphous CaCO3 appears to be very stable at lower values of relative humidity.
Calcium acetoacetate, Ca(OAcAc)2, was exposed 7, 30 and 365 days to different values of relative humidity (33%, 48%, 75% and 96%) at 40 °C in order to study its transformation to CaCO3. The resulting Ca(OAcAc)2 decomposition and the time dependence of the phase transformations were monitored and critically evaluated by Fourier transform infrared spectroscopy, field emission scanning electron microscopy and X-ray powder diffraction. The impact of relative humidity on CaCO3 polymorph formation was thoroughly assessed. In all of the conditions used and for all ageing periods, the formed crystal structure is found to be vaterite. At the lowest relative humidity (33%), the amorphous CaCO3 remains more or less almost untransformed even after one year of exposure. It is proposed that the reason for the stability of amorphous CaCO3 is due to the limited amount of physisorbed water on the surfaces of the particles, which is considered the driving force for its transformation. However, the carbonation process is faster in the case of the highest humidity (96%). The findings are not only important for better solutions in the field of cultural heritage, but also shed new light on the fundamental mechanism of CaCO3 crystallization.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Hybrid phenol-formaldehyde (PF) resins represent one of the most important niche groups of binding systems for composites. New industrial needs, environmental requirements, and price fluctuations ...have led to further research on materials with enhanced mechanical and thermal properties. The preparation of novel hybrid materials can be achieved by inclusion of various elements or functional groups in the organic polymer phenolic framework. Herein, we report the synthesis and characterization of a PF-based hybrid material with different nanoscale silicone species and ZnAl-layered double hydroxide (LDH). The main goals of this study were to improve the synthetic pathways of hybrid resin, as well as to prepare granulated composite materials and test samples and determine their characterization. Added inorganic species increased the glass-transition temperature by a minimum of 8 °C, which was determined using differential scanning calorimetry (DSC). Rheological properties (melting viscosity and flow distance) of the hybrid resin were measured. The homogeneity of distribution of added species across the organic matrix was evaluated with scanning electron microscopy (SEM). With synthesized new hybrid-binding systems, we prepared different granulated composite materials and evaluated them with the measurements of rheological properties (flow curing characteristics). Tensile strength of samples, prepared from granulated composite material, improved by more than 5%.
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The durability of Portland cement mortars is often affected by environmental factors, which can cause physicochemical and mechanical degradation processes. In this study, the performance of three ...products, calcium acetoacetate and calcium tetrahydrofurfuryloxide dissolved in two different solvents developed and tested as stone consolidants, was evaluated in terms of crack filling or sealing and consolidation. Realistic cracks were induced in quasibrittle cement mortar prisms using a custom-designed test rig. The effectiveness and the performance of the considered treatments, investigated on specimens, were evaluated by optical and scanning electron microscopy, colourimetry, water absorption rate, ultrasonic pulse velocity, and surface hardness measurements. Results revealed that, in the examined conditions, the products were more suitable as surface consolidants than as crack fillers.
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The mining tradition in Litija, dating back to the Iron Age, involved the intensive use of wood in the mines, especially for support and protection. The Sitarjevec mine was reopened for tourism in ...2017, and the central tunnel was opened in 2021. Wood remains a key material in the mines, although other materials have replaced it in the past. The wood used is subject to decay due to high humidity and fungi such as the mine fungus. This fungus can cause wood decomposition and is common in the humid environments of mines. The presence of fungi is important as it can affect visitors to the mine. The high relative humidity (96.6%) and constant temperature (10.1°C) in the mine create favourable conditions for fungal growth, although the relatively low temperature is not a limiting factor for wood decay. The high concentration of fungal spores in the mine is explained by the presence of fungi in the mine itself. In addition, we have observed that the wood contains a high level of inorganic contaminants and many crystals.
In the process of protection and consolidation of valuable materials, the efficiency is the crucial property that needs to be considered. TiO₂/ZnAl layered double hydroxide (LDH) coating and ...silicate- and carbonate-based consolidants were synthesized and proposed to be used for protection and consolidation of four porous mineral substrates: brick, stone, render and mortar. The photocatalytic efficiency of TiO₂/ZnAl LDH coating, as well as consolidation efficiency of two consolidants, both applied on model substrates, were studied. The photocatalytic coating showed significant activity and performed well after the durability tests involving rinsing and freezing/thawing procedures. After treatment with both consolidants, a serious enhancement of consolidation of the used substrates was found. On the other hand, the application of TiO₂/ZnAl LDH, as well as consolidants, caused negligible changes in the water vapour permeability values and in appearance of the porous mineral substrates, indicating a high level of compatibility.
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Light eutrophication in show caves and other light-deprived humid environments can support visible growth of microbial mats, with photoautotrophs as the dominant group of organisms. Photosynthetic ...pigments of aerophytic cyanobacteria and eukaroytic algae impose a greenish patina upon surfaces to which -- with other community members -- they adhere strongly. Diverse eukaryotic algae, fungi, flagellates and amoebozoans were also identified within the community. These "human induced diversity hotspots" in caves are responsible for the biodeterioration of colonized surfaces that is a common result of the synergistic effects of phototrophs and heterotrophs. When sites become colonized by higher plants, such as mosses, liverworts and ferns in species succession, irreversible biodeterioration impact on rocks and speleothems becomes an even more urgent issue. Historical inscriptions and rock-art paintings are particularly sensitive to biodeterioration. Lampenflora also affects components of the cave fauna, which not only graze upon it, but also facilitate its dispersal to other parts of the caves. It can be considered a direct indicator for light eutrophication and of the available energy within the cave ecosystem.
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A novel environmentally friendly method for
in situ
formation of CaCO
3
deep inside a wood's structure is presented. The method is based on vacuum-pressure impregnation using a one-component ...treatment medium - a water solution of calcium acetoacetate - and a single stage process to significantly improve the fire retardancy of the treated material.
In order to improve the fire retardancy of wood the eco-friendly method for
in situ
formation of CaCO
3
deep inside the wood's structure was proposed by the vacuum-pressure impregnation of only one component - water solution of calcium acetoacetate.
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.
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•Presented ecological modification of wood can be an alternative to biocides.•A significant improvement in the fungal durability of wood was achieved.•Thermal modification and mineralisation work synergistic against wood decay fungi.•The reasons for a synergistic effect of combining methods were proposed.•The mass loss decreased from 41% for native to 6% for combined modified beechwood.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Single edge-notched three-point bending tests (SEN-TPB) for mode I were utilized to experimentally evaluate fracture properties of adhesive bondlines in European beech (Fagus Sylvatica L.). The ...bondline was examined at two anatomical planes with TR and RT orientation and at control and two elevated temperatures (70°C and 140°C). Among epoxy (EPI), melamine-urea formaldehyde (MUF), and polyurethane (PUR) adhesives, the highest average critical energy G
c
with 0.80 N/mm and fracture energy G
f
with 1079.4 N/mm were obtained for EPI in the TR plane and under standard climate conditions (20°C/65% relative humidity), followed by MUF (G
c
= 0.50 N/mm and G
f
= 620 N/mm) and PUR (G
c
= 0.25 N/mm and G
f
= 290.9 N/mm), respectively. PUR was least effected by elevated temperature, and no significant differences for G
c
and G
f
between TR and RT bondline orientations were found for MUF and PUR treated at 20°C/65% relative humidity while comparisons between other factors varied significantly. Treatment of specimens at elevated temperatures resulted in reduced fracture performance regardless of wood grain orientation or the adhesive system.
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