Toxic metals in cyanobacterial mat of Big Lachman Lake, James Ross Island, Antarctica.

The northern part of James Ross Island is the largest deglaciated area in the Antarctic Peninsula region with a unique ecosystem created during the Late Glacial. This research aims to evaluate the degree of contamination of the locality with toxic metals (As, Hg, Cd, and Pb) through bioindicators in the aquatic environment-colonies of cyanobacteria and algae. For this purpose, bottom lake sediments of Big Lachman Lake were studied for contents of Fe, As, Hg, Cd, Pb, Cr, Co, Ni, Cu, and Zn, as well as samples of cyanobacterial mat, in which Fe, As, Hg, Cd, and Pb were determined. Metal contents were determined by means of inductively coupled plasma optical emission spectrometry and atomic absorption spectrometry. The contents of metals in sediments did not differ from the usual values in the area of the Antarctic Peninsula. The bioaccumulation of metals in cyanobacterial mat was evaluated by calculating enrichment factors (the calculation to Fe as a reference element). According to this method, moderate pollution of Big Lachman Lake was confirmed for Hg and Cd.

CaCO3 Polymorphs Used as Additives in Filament Production for 3D Printing.

Nowadays, additive manufacturing-also called 3D printing-represents a well-established technology in the field of the processing of various types of materials manufacturing products used in many industrial sectors. The most common type of 3D printing uses the fused filament fabrication (FFF) method, in which materials based on thermoplastics or elastomers are processed into filaments. Much effort was dedicated to improving the properties and processing of such printed filaments, and various types of inorganic and organic additives have been found to play a beneficial role. One of them, calcium carbonate (CaCO3), is standardly used as filler for the processing of polymeric materials. However, it is well-known from its different applications that CaCO3 crystals may represent particles of different morphologies and shapes that may have a crucial impact on the final properties of the resulting products. For this reason, three different synthetic polymorphs of CaCO3 (aragonite, calcite, and vaterite) and commercially available calcite powders were applied as fillers for the fabrication of polymeric filaments. Analysis of obtained data from different testing techniques has shown significant influence of filament properties depending on the type of applied CaCO3 polymorph. Aragonite particles showed a beneficial impact on the mechanical properties of produced filaments. The obtained results may help to fabricate products with enhanced properties using 3D printing FFF technology.

Lightweight Concretes with Improved Water and Water Vapor Transport for Remediation of Damp Induced Buildings.

Most of the historical and old building stock in Europe are constructed from masonry, when brick, stones, or their combination are bound with traditional mortars. Rising damp, due to accompanying effects, is the main factor influencing the quality of indoor climate as well as having an important impact on the durability of masonry structures. In this study, new types of lightweight concrete with waste aggregate content as a suitable material for remediation of damp damaged masonries were designed and tested. Alternative aggregate served as silica sand substitution in the range of 0-100 vol.%. Basic structural properties, mechanical resistance, water, and water vapor transport properties were measured after 28 days of water curing and were compared with dense reference concrete and with traditional masonry materials as well. Moreover, the porous structure of produced concretes and changes caused by usage of alternative aggregate usage were evaluated with the mercury intrusion porosimetry (MIP) technique. Obtained experimental data showed the suitability of modified concretes with 25-50 vol.% of waste aggregate content to ensure acceptable strength and hydric properties, and these properties were found to be comparable with masonry structures and materials used in the past.

The Design and Material Characterization of Reclaimed Asphalt Pavement Enriched Concrete for Construction Purposes.

Reclaimed asphalt pavement (RAP) is a valuable commodity originating during processes of road/highways rehabilitations, resurfacing in the cases of the revelation of underneath-placed layers. Removed material can be successfully recycled and utilized as a supplementing material for new hot asphalt mixes. However, its dosages are limited because of variations in properties of aged bitumen compared to fresh material and, thus, a significant amount of waste material is remaining as waste products. Nonetheless, this commodity may find usage in the construction industry that suffers from a shortage of high-quality and easily available aggregates. This work aimed to investigate the optimal substitution of mined natural aggregate with commonly available RAP in order to produce composites with the comparable mechanical performance of reference ordinary Portland concrete. The aggregate substitutions up to 100% with RAP have been studied with a combination of mechanical and analytical techniques. Obtained experimental data showed changes in the porous structure, mineralogy, and in the amount of formed cement-related hydration products that influenced the mechanical performance of produced composites. Composite with 10% of natural aggregate substitution with RAP has shown the strength class C16/20 after 28 days of water curing, according to the EN 206-1. Such innovative products could be utilized in the construction industry. The usage of waste RAP could contribute to preservation of our environment for future generations.

Effect of Cyclotriphosphazene-Based Curing Agents on the Flame Resistance of Epoxy Resins.

Epoxy resins are characterized by excellent properties such as chemical resistance, shape stability, hardness and heat resistance, but they present low flame resistance. In this work, the synthesized derivatives, namely hexacyclohexylamino-cyclotriphosphazene (HCACTP) and novel diaminotetracyclohexylamino-cyclotriphosphazene (DTCATP), were applied as curing agents for halogen-free flame retarding epoxy materials. The thermal properties and combustion behavior of the cured epoxy resins were investigated. The obtained results revealed that the application of both derivatives significantly increased flame resistance. The epoxy resins cured with HCACTP and DTCATP exhibited lower total heat release together with lower total smoke production compared to the epoxy materials based on conventional curing agents (dipropylenetriamine and ethylenediamine). Comparing both derivatives, the HCACTP-cured epoxy resin was found to provide a higher flame resistance. The designed novel class of epoxy materials may be used for the preparation of materials with improved flame resistance properties in terms of flame spreading and smoke inhibition.

Synthetic calcium carbonate improves the effectiveness of treatments with nanolime to contrast decay in highly porous limestone.

Three synthetized polymorphs of calcium carbonate have been tested in combination with the suspension of nanolime particles as potential consolidating agents for contrasting stone decay and overcome some of the limitations of nanolime agents when applied to substrates with large porosity. The modifications induced in the pore network of the Maastricht limestone were analyzed with microscopy and in a non-invasive fashion with small angle neutron scattering and synchrotron radiation micro-computed tomography. A reduction in porosity and pore accessibility at the micrometric scale was detected with the latter technique, and ascribed to the improved pore-filling capacity of the consolidation agent containing CaCO3 particles. These were found to be effectively bound to the carbonated nanolime, strengthening the pore-matrix microstructure. Penetration depth and positive effect on porosity were found to depend on the particle size and shape. Absence of significant changes in the fractal nature of the pore surface at the nanoscale, was interpreted as indication of the negligible contribution of nanolime-based materials in the consolidation of stones with large porosity. However, the results indicate that in such cases, their effectiveness may be enhanced when used in combination with CaCO3 particles, owing to the synergic effect of chemical/structural compatibility and particle size distribution.