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This paper presents the effects of long-term exposure of concrete structures to marine environment using as an example concrete blocks of a pier exposed to seawater for more than three decades. The blocks were tested to determine their mechanical characteristics (compressive strength), durability (gas permeability and capillary absorption), and chemical properties (quantity of chloride and sulphate ions). In addition, concrete behaviour in sea water was modelled using software packages Stadium and Conclife.

Abstract Marine microbial communities form the basis for the functioning of marine ecosystems and the conservation of biodiversity. With the application of metagenomics and metatranscriptomics in marine environmental studies, significant progress has been made in analysing the functioning of microbial communities as a whole. These molecular techniques are highly dependent on reliable, well-characterised, comprehensive and taxonomically diverse sequenced reference transcriptomes of microbial organisms. Here we present a set of 12 individual transcriptome assemblies derived from 6 representative diatom species from the northern Adriatic Sea grown under 2 environmentally relevant growth conditions (phosphate replete vs. phosphate deprived). After filtering the reads and assembly, an average number of 64,932 transcripts per assembly was obtained, of which an average of 8856 were assigned to functionally known proteins. Of all assigned transcripts, an average of 6483 proteins were taxonomically assigned to diatoms (Bacillariophyta). On average, a higher number of assigned proteins was detected in the transcriptome assemblies of diatoms grown under replete media condition. On average, 50% of the mapped proteins were shared between the two growth conditions. All recorded proteins in the dataset were classified into 24 COG categories, with approximately 25% belonging to the unknown function and the remaining 75% belonging to all other categories. The resulting diatom reference database for the northern Adriatic, focussing on the response to nutrient limitation as characteristic for the region and predicted for the future world oceans, provides a valuable resource for analysing environmental metatranscriptome and metagenome data. Each northern Adriatic transcriptome can also be used by itself as a reference database for the (meta)transcriptomes and gene expression studies of the associated species that will be generated in the future.

The ways in which concrete properties are influenced by waste tyre recyclates, used as secondary raw materials, are presented in the paper. Taking advantage of these properties, several special-purpose construction products, containing raw materials obtained by tyre recycling, have been developed at the Faculty of Civil Engineering, University of Zagreb. Each of these innovative products represents an environment-friendly, functional and cost-effective alternative to products traditionally used in engineering practice.

Understanding the mechanisms that alter the ground penetrating radar (GPR) electromagnetic wave propagation as a result of reinforcement corrosion is pivotal for accurate assessment of the corrosion of reinforced concrete (RC) structures. Nevertheless, the behaviour of the GPR signal during the complex corrosion process is not thoroughly understood. In this study, finite-difference time-domain (FDTD) modelling was used to analyse the effects of corrosion-related parameters, i.e., moisture, chlorides, and corrosion products, on the electric field strength. This study aims to expand the database on numerical simulations of GPR signal behaviour in corrosive environments. It also addresses the knowledge gap in modelling the frequency-dependent properties of concrete and iron oxides. Modelling approach adopted in the study was validated with experimental data obtained on laboratory specimens that correspond to the numerical models in terms of geometry and condition.

Plankton studies serve as a basis for marine ecosystem research, but knowledge of marine plankton is still incomplete due to its extreme taxonomic and functional complexity. The application of metabarcoding is very valuable for the characterisation of the plankton community. The plankton community of the Southern Adriatic is subject to strong environmental fluctuations and changes, which underlines the need for frequent, reliable and comprehensive characterisation of the plankton. The aim of this study was to determine the taxonomic composition and seasonal distribution of eukaryotic plankton in the Southern Adriatic. Plankton samples were collected monthly for one year at the coastal station of the Southern Adriatic and metabarcoding was used for taxonomic identification. The results showed a high taxonomic diversity and dynamic seasonal distribution patterns for both the protist and metazoan plankton communities. Metabarcoding revealed both the core, year-round plankton community and previously unrecorded plankton organisms in the Southern Adriatic. The results provide for the first time a comprehensive overview of the plankton community in this area by metabarcoding. The identified seasonal patterns of plankton genera and species in the Southern Adriatic will contribute to the understanding of plankton interactions and future changes in community diversity characterisation.

Implementation of DNA metabarcoding for diatoms for environmental monitoring is now moving from a research to an operational phase, requiring rigorous guidelines and standards. In particular, the first steps of the diatom metabarcoding process, which consist of sampling and storage, have been addressed in various ways in scientific and pilot studies and now need to be rationalised. The objective of this study was to compare three currently applied preservation protocols through different storage durations (ranging from one day to one year) for phytobenthos and phytoplankton samples intended for diatom DNA metabarcoding analysis. The experimental design used samples from four freshwater and two marine sites of diverse ecological characteristics. The impact of the sample preservation and storage duration was assessed through diatom metabarcoding endpoints: DNA quality and quantity, diversity and richness, diatom assemblage composition and ecological index values (for freshwater samples). The yield and quality of extracted DNA only decreased for freshwater phytobenthos samples preserved with ethanol. Diatom diversity was not affected and their taxonomic composition predominantly reflected the site origin. Only rare taxa (< 100 reads) differed among preservation methods and storage durations. For biomonitoring purposes, freshwater ecological index values were not affected by the preservation method and storage duration tested (including ethanol preservation), all treatments returning the same ecological status for a site. This study contributes to consolidating diatom metabarcoding. Thus, accompanied by operational standards, the method will be ready to be confidently deployed and prescribed in future regulatory monitoring.

In line with current ”green” transport initiatives, Croatia plans to build over the next investment period a high speed railway line which will connect central Croatia and its capital with coastal regions of the country. According to design documents, the track system will be built using ballastless concrete solutions. In the scope of the project “Concrete track system – ECOTRACK”, researchers from the University of Zagreb - Faculty of Civil Engineering analysed a new material, i.e. the rubberized hybrid fibre reinforced concrete (RHFRC), in order to find out whether its properties are adequate for the proposed concrete track system. The RHFRC contains by-products from mechanical recycling of waste tyres (rubber and steel fibres). The study of fibre and rubber interaction and their contribution to mechanical properties of the fibre reinforced concrete is presented, as extensive research on positive interaction between industrial and recycled steel fibres has not as yet been made. The results show that the RHFRC is an innovative, sustainable and cost-effective concrete, which is fully compliant with criteria prescribed in relevant standards.

Efforts to improve the environmental sustainability of the construction industry involve exploring waste materials, environmentally friendly production processes and high performance materials like ultra-high-performance concrete (UHPC). Despite UHPC’s benefits, its widespread use is hampered by its high cost and environmental concerns. To address this, limestone filler and metakaolin were used to replace 30% of the cement, while recycled tyre steel fibres (RTSF) and production waste carbon fibres (CF) replaced the conventional factory-made fibres. Eight mixes underwent various tests in fresh state and hardened state, revealing initial negative effects of supplementary cementitious materials (SCMs) on strength and capillary absorption, which improved considerably over time. Fibres addition, especially hybrid fibres, increased strength and toughness without significantly affecting modulus of elasticity. RTSF at 1 vol% and 1.5 vol% positively impacted compressive strength and toughness, while 1 vol% CF improved flexural strength and capillary water absorption. Optimal contents varied for the hybrid fibre mixes depending on the tested property, with overall best results in compressive strength, toughness and specific energy absorption. The hybrid mixes outperformed the RTSF mixes but lagged behind the CF mixes in terms of flexural strength and capillary water absorption. A multi-criteria analysis was conducted to determine the optimum mix design, taking into account factors such as performance, cost, and environmental impact. This analysis highlighted the potential of the supplementary materials and fibres to improve the environmental and economic efficiency of UHPC while maintaining or even improving the tested properties.

In this review, we toxicologically assessed the naturally occurring toxin domoic acid. We used the One Health approach because the impact of domoic acid is potentiated by climate change and water pollution on one side, and reflected in animal health, food security, human diet, and human health on the other. In a changing environment, algal blooms are more frequent. For domoic acid production, the growth of Pseudo-nitzschia diatoms is of particular interest. They produce this toxin, whose capability of accumulation and biomagnification through the food web impacts other organisms in the ecosystem. Domoic acid targets nervous system receptors inducing amnestic shellfish poisoning, among other less severe health-related problems. However, the impact of domoic acid on non-target cells is rather unknown, so we reviewed the currently available literature on cytogenetic effects on human and animal cells. The results of different studies indicate that domoic acid has the potential to induce early molecular events, such as oxidative imbalance and DNA damage, thus posing an additional threat which needs to be thoroughly addressed and monitored in the future.

The northern Adriatic is characterised as the coldest and most productive marine area of the Mediterranean, which is due to high nutrient levels introduced by river discharges, the largest of which is the Italian Po River (at the same time also the largest freshwater input into the Mediterranean). The northern Adriatic is a very shallow marine ecosystem with ocean current patterns that result in long retention times of plankton in the area. The northern Adriatic phytoplankton biodiversity and abundance are well-studied, through many scientific and long-term monitoring reports. These datasets were based on phytoplankton morphological traits traditionally obtained with light microscopy. The most recent comprehensive eastern Adriatic phytoplankton checklist was published more than 20 years ago and is still valuable today. Since phytoplankton taxonomy and systematics are constantly being reviewed (partly also due to new molecular methods of species identification that complement classical methodologies), checklists need to be updated and complemented. Today, metabarcoding of molecular markers gains more and more importance in biodiversity research and monitoring. Here, we report the use of high throughput sequencing methods to re-examine taxonomic richness and provide updated knowledge of phytoplankton diversity in the eastern northern Adriatic to complement the standardised light microscopy method.This study aimed to report an up-to-date list of the phytoplankton taxonomic richness and phylogenetic relationships in the eastern northern Adriatic, based on sequence variability of barcoding genes resolved with advanced molecular tools, namely metabarcoding. Here, metabarcoding is used to complement standardised light microscopy to advance conventional monitoring and research of phytoplankton communities for the purpose of assessing biodiversity and the status of the marine environments. Monthly two-year net sampling targeted six phytoplankton groups including Bacillariophyceae (diatoms) and Chrysophyceae (golden algae) belonging to Ochrophyta, Dinophyceae (dinoflagellates), Cryptophyceae (cryptophytes), Haptophyta (mostly coccolithophorids) and Chlorophyta with Prasinophyceae (prasinophytes) and Chlorophyceae (protist green algae). Generated sequence data were taxonomically assigned and redistributed in two kingdoms, five classes, 32 orders, 49 families and 67 genera. The most diverse group were dinoflagellates, comprising of 34 found genera (48.3%), following by diatoms with 23 (35.4%) and coccolithophorids with three genera (4.0%). In terms of genetic diversity, results were a bit different: a great majority of sequences with one nucleotide tolerance (ASVs, Amplicon sequence variants) assigned to species or genus level were dinoflagellates (83.8%), 13.7% diatoms and 1.6% Chlorophyta, respectively. Although many taxa have not been detected that have been considered as common in this area, metabarcoding revealed five diatoms and 20 dinoflagellate genera that were not reported in previous checklists, along with a few species from other targeted groups that have been reported previously. We here describe the first comprehensive 18S metabarcode inventory for the northern Adriatic Sea.

Renewables-based power grid expansion has increased the use of wood biomass as a low-carbon fuel, resulting in the generation of predominantly inorganic wood biomass ash (WBA) as waste during biomass combustion. The conservation of historically valuable, damaged, and energy-inefficient buildings can help downsize carbon emissions and energy consumption, while promoting the use of alternative repair materials, including unavailing materials such as WBA, and implementing zero-waste measures. This study aims to underscore the importance of a proactive approach in managing WBA and its application in artificial hydraulic lime (AHL) mortars. Hybrid lime mortars were prepared by combining natural hydraulic lime (NHL) as the primary binder with fly wood biomass ash (WBA) as the secondary substitute, using different mass ratios of NHL to WBA (100:0, 80:20, and 70:30). The experimental framework encompassed interconnected analytical steps, ranging from binder analysis to paste and mortar preparation. The chemical and mineralogical composition, physical properties, and reactivity of WBA were evaluated to determine the appropriate proportion of WBA for low-carbon AHL binder formulation. Prior to mortar mixing, the water demand, setting time, and soundness of the AHL pastes were assessed. The effects of each AHL binder blend on the mechanical properties of the AHL mortars were analyzed based on compressive and flexural strength measurements after 28 days of curing under different CO2 and moisture conditions (CO2~400 ppm at 70% RH and 95% RH; CO2~30,000 ppm at 60% RH). Additionally, changes in the porous structure were studied. Notwithstanding the greatly prolonged setting time, the results indicate that the mechanical properties of AHL mortars can be enhanced by the addition of WBA in a moderate ratio, empowering the development of environmentally friendly lime mortars suitable for conservation purposes.

Synthetic fibres are often used to reinforce cementitious composites. However, their production has significant negative environmental impact. An ecological alternative could be to use waste fibre if their properties are found to be satisfactory. Therefore, the main objective of this study was to determine if selected waste fibres could withstand an aggressive and highly alkaline environment of cementitious composites. Three types of production waste fibres (alkali-resistant glass fibres, AR-GF, basalt fibres, BF and carbon fibres, CF and recycled tyre polymer fibres RTPF) were exposed to a synthetic pore solution simulating the cement matrix condition for 90 days. The mechanical properties of the production waste fibres and the morphology determined by scanning electron microscopy were the best predictors of fibre resistance. The sizing of the treated production waste fibres partially (CF) or completely (AR-GF, BF) decomposed. The pronounced deterioration of the BF structure was accompanied by a complete deterioration of the mechanical properties. A slight deterioration of mechanical properties was also observed in CF and to an even greater extent in AR-GF. The RTPFs were too short for mechanical measurements, so a combination of Fourier transform infrared spectroscopy and thermal analysis was required to evaluate effects of exposure to synthetic pore solution. The retained properties of treated RTPF seemed to be at least equivalent to those of AR-GF. Overall, the alkaline resistance of all studied waste and recycled tyre polymer fibres appears to be sufficient to restrain early age deformation of cementitious composite.

Abstract The northern Adriatic is highly productive and shallow area characterized by numerous spatio-temporal gradients (e.g. nutrients, salinity, temperature). It is strongly influenced by numerous freshwater inputs, mainly from Po river. Its current systems as well as Po river, generates gradients of phosphate availability with an expressed N/P imbalance and phosphate limitation. A number of recent studies characterized these gradients as major factors affecting abundance and composition of microphytoplankton communities. Focus of this study is on two Leptocylindrus species, Leptocylindrus aporus (F.W. French & Hargraves) D. Nanjappa & A. Zingone 2013 and Leptocylindrus hargravesii D. Nanjappa & A. Zingone 2013. Species belonging to Leptocylindrus genus are frequently observed and have high abundances and also high contributions to the microphytoplankton community in this area. We focused on their morphological and physiological responses to phosphate limitation in situ and also performed in vitro experiments. In this study we report data on species specific growth rates under phosphorus (P) deplete and P rich conditions, localization and characteristics of alkaline phosphate activity, phosphate uptake rates as well as their morphological differences in P deplete versus P rich conditions. Our in vitro experiments showed that both Leptocylindrus species morphologically reacted similarly to phosphorus depletion and showed significantly elongated pervalvar axis in P depleted conditions if compared to P rich conditions. Also average chain lengths increased when in P depleted conditions. Two previously mentioned adaptations indicate their tendency to increase cellular surface areas available for alkaline phosphatase. Chlorophyll fluorescence of both species significantly decreased in P depleted medium. Although both species morphologically reacted similarly, our experiment demonstrated significant differences in physiological reactions to P depleted conditions.

An essential step in the condition assessment of reinforced concrete structures and evaluation of the residual capacity is the determination of the arrangement and quantity of reinforcement as well as the geometry of the structural elements. The objective of this paper is to present the fundamentals in the application of two non-destructive methods, cover meter and ground penetrating radar, in the determination of the above structural features. A comparison of the two methods is presented and their capabilities, advantages and disadvantages are shown through nine case studies.

This paper presents the pilot project of application of recycled aggregate during construction of a new day hospital in Zadar. The project included the demolition of an existing hospital building and the use of generated construction waste as recycled aggregate in the construction of a part of the building. The 16/32 mm fraction of aggregate was obtained by mechanical processing of the generated waste which was then tested in accordance with the HRN EN 206 and HRN EN 12620 standards. Four concrete mixes were prepared, and the fresh (slump, density, air content) and hardened properties were tested (compressive strength, modulus of elasticity, capillary absorption, water permeability, drying shrinkage). The obtained results confirm that by complying with the standards for recycled aggregates and knowing their origin it is possible to produce concrete with properties equivalent to those of ordinary concrete for specified durability conditions.

The trend of wood biomass use as a renewable energy source has contributed to an increase in the quantity of wood biomass ash (WBA) that is regarded as waste. Currently, 70 % of WBA is landfilled, 20 % is used in agriculture, and 10 % is used for other purposes. The aim of this paper is to carry out an extensive analysis of the current situation regarding WBA production in Croatia and other European countries. An overview of the types and properties of WBA in relation to the type of wood biomass is given, and parameters relevant for WBA use in concrete industry are presented.

Self-compacting concrete requires a special composition with an increased proportion of fine particles and larger volumes of paste compared to traditional vibrated concrete. Larger volumes of paste increase autogenous deformation, which can cause microcracking of concrete. The aim of this paper is to research the possibility of using recycled polymer fibers obtained from end-of-life tires to prevent micro cracking due to autogenous deformation in self-compacting concrete. Mixes of self-compacting concrete containing 1 and 2 kg/m3 of recycled tire polymer fibers and reference mixes were prepared and tested. Beside autogenous deformation, fresh state properties as well as compressive strength at the age of 3, 7 and 28 days were tested. The results of the performed laboratory tests indicate that the use of recycled tire polymer fibers is effective for the reduction of early autogenous deformation with insignificant difference in compressive strength at tested ages.

Properties of concrete elements under fatigue load can be enhanced by adding steel fibres to the concrete mixture. An experimental study of recycled steel fibre reinforced concrete elements subjected to cyclic load is described. Fatigue design models are presented according to the fib Model Code 2010, ACI 215, and JSCE guidance. Design model calculations are compared to the results of experimental analyses. It can be observed that, as a rule, all design models underestimate the experimentally obtained fatigue resistance of concrete elements. The adjustment of the fib Model Code design model is proposed.

Chaetoceros peruvianus is a marine diatom species with circumglobal distribution. While frequently observed, it appears never to dominate the marine phytoplankton community hence it can be characterized as a rather opportunistic, generalistic species. Here we present ecological interpretations from a long-term data set on marine microphytoplankton in the northern Adriatic Sea, where the abundancies and relative contributions of C. peruvianus were observed along a set of steep ecological gradients. Limited supply of dissolved inorganic phosphate was identified as the driving ecological factor for this ecosystem. In parallel C. peruvianus was cultivated in monoclonal cultures and its morphological and physiological reaction to replete and phosphorus depleted medium was analysed. C. peruvianus reacted to phosphorus depletion by an increase in cell height and length as well as thickness and length of setae. This morphological reaction included an increase in cellular volume and calculated carbon content. Additionally, it represents the transition between two described morphological varieties, C. peruvianus and C. peruvianus var. robusta. C. peruvianus showed a significant induction of extracellular alkaline phosphatase activity if grown in phosphate depleted medium. Microscopical analysis demonstrated this activity to be located exclusively on the setae of the cells.

Different types of fibres are often used in concrete to prevent microcracking due to shrinkage, and polypropylene fibres are among the most often used ones. If not prevented, microcracks can lead to the development of larger cracks as drying shrinkage occurs, enabling penetration of aggressive substances from the environment and reducing durability of concrete structures. The hypothesis of the present research is that polypropylene fibres, used in concrete for controlling formation of microcracks due to shrinkage, can be replaced with recycled polymer fibres obtained from end-of-life tyres. To test the hypothesis, concrete mixtures containing polypropylene fibres and recycled tyre polymer fibres were prepared and tested. Experimental programme focused on autogenous, free, and restrained shrinkage. It was shown that PP fibres can be substituted with higher amount of recycled tyre polymer fibres obtaining concrete with similar shrinkage behaviour. The results indicate promising possibilities of using recycled tyre polymer fibres in concrete products. At the same time, such applications would contribute to solving the problem of waste tyre disposal.