Influence of the compaction method on the bond between steel and concrete in composite columns

The aim of the present paper is to assess the impact of the compaction method on the bond between concrete and steel in composite columns. The full scale laboratory tests show that the bond between vibrated concrete and steel is better than in case of self-compacting concrete. It is indicated that the higher concrete compressive plastic stress level the more strength the bond. The results obtained on the basis of laboratory tests are compared with calculations performed according to the Eurocode 4. Moreover, the bond considered is modeled by the FE method. The measured strains and thus computed stresses compare favorably with the FE predictions

Local populations of endangered Maculinea (Phengaris) butterflies are flood resistant

Semi-natural wet meadows are threatened by drainage, the abandonment of traditional management and climate change. The large blue butterflies Maculinea teleius and M. nausithous are flagship species associated with wet meadows and are the targets of many conservation programmes. However, there is little knowledge on the impact of natural catastrophes, such as floods, on the persistence of these butterflies. In our study we tested how a flood that resulted in the temporary inundation of meadows affected populations of M. teleius and M. nausithous. Studies were conducted in two consecutive seasons of 2009 (with ‘normal’ weather) and 2010 (with extreme rainfall and a consequent flood in May) in a wet meadow complex located in the Vistula River valley in southern Poland. In both years the abundance of adults was estimated for each local habitat patch (n = 55) within sympatric metapopulations of both species. Additionally, in June 2010, i.e. directly after the flood and shortly before the flight period, a total of 754 Myrmica ant nests in 10 habitat patches (6 inundated vs. 4 not inundated) were checked for the presence of Maculinea larvae and pupae. We found no impact of inundation on year-to-year changes in adult population sizes. The probability of occurrence of Maculinea larvae and pupae in ant nests was higher in temporarily inundated meadows. Our results indicate that temporary inundation occurring after long-term downpours does not negatively affect the investigated species even during the larval period in ant nests at ground level. This provides an argument against drainage works in wet meadows with Maculinea butterflies

Invasive alien plants affect grassland ant communities, colony size and foraging behaviour

Ants are dominant members of many terrestrial ecosystems and are regarded as indicators of environmental changes. However, little is known about the effects of invasive alien plants on ant populations, particularly as regards the density, spatial distribution and size of ant colonies, as well as their foraging behaviour. We addressed these questions in a study of grassland ant communities on five grasslands invaded by alien goldenrods (Solidago sp.) and on five non-invaded grasslands without this plant. In each grassland, seven 100 m plots were selected and the ant colonies counted. Ant species richness and colony density was lower in the plots on the invaded grasslands. Moreover, both of these traits were higher in the plots near the grassland edge and with a higher number of plant species in the grasslands invaded by goldenrods but not in the non-invaded ones. On average, ant colony size was lower on the invaded grasslands than the non-invaded ones. Also, ant workers travelled for longer distances to collect food items in the invaded areas than they did in the non-invaded ones, even after the experimental removal of some ant colonies in order to exclude the effect of higher colony density in the latter. Our results indicate that invasive alien goldenrods have a profound negative effect on grassland ant communities which may lead to a cascade effect on the whole grassland ecosystem through modification of the interactions among species. The invasion diminishes a major index of the fitness of ants, which is a colony's size, and probably leads to increased foraging effort of workers. This, in turn, may have important consequences for the division of labour and reproductive strategies within ant colonies

Morphology of caterpillars and pupae of European Maculinea species (Lepidoptera: Lycaenidae) with an identification table

Ofthe four recognized Maculinea species that occur in Europe, three (M. teleius, M. nausitlzous, and M. alcon) are found on damp meadows, and may co-occur; sometimes their larval instars even occupy the same host ant nest. It is, therefore, important to be able to distinguish between the caterpillars of these species for effective conservation. We present the morphology of the larvae and pupae of these three species, and a simple key to their identification. Inter-specific differences among larvae and pupae, and within-species differences among larval instars, are underlined in order to enable their proper identification. The length, colour and distribution of bristles are considered the best features for species and instar identification. The morphology ofthe described species is compared with that of the other European species, M. arion

Carbonation of concrete cover of reinforcement as a cause of loss of durability of structures

The article discusses the physical and chemical mechanisms of the carbonation phenomenon itself, as well as points out the synergistic effect of frost destruction and concrete carbonation on reinforced concrete elements. Examples of structural damage from engineering practice in the diagnosis of reinforced concrete structures are presented. Two cases of frost and carbonation damage of precast reinforced concrete elements are analyzed. It was noted that the most common cause of damage to concrete structures is the lack of frost resistance. Carbonation of concrete leads to deprivation of the protective properties of the concrete lagging against the reinforcing steel. The examples cited include precast elements that, for technical reasons, had a relatively small lagging thickness. The first one relates to the thin walled elevation elements, which are exploited during 60 years and the second relates to the energetic poles with very advanced concrete corrosion damage. The examples given of corrosion of concrete and reinforcement of elements indicate that synergistic environmental interactions can intensify the destruction of elements

Plant establishment and invasions : an increase in a seed disperser combined with land abandonment causes an invasion of the non-native walnut in Europe

Successful invasive species often are established for a long time period before increasing exponentially in abundance. This lag phase is one of the least understood phenomena of biological invasions. Plant invasions depend on three factors: a seed source, suitable habitat and a seed disperser. The non-native walnut, Juglans regia, has been planted for centuries in Central Europe but, until recently, has not spread beyond planted areas. However, in the past 20 years, we have observed a rapid increase in walnut abundance, specifically in abandoned agricultural fields. The dominant walnut disperser is the rook, Corvus frugilegus. During the past 50 years, rooks have increased in abundance and now commonly inhabit human settlements, where walnut trees are planted. Central Europe has, in the past few decades, experienced large-scale land abandonment. Walnut seeds dispersed into ploughed fields do not survive, but when cached into ploughed and then abandoned fields, they successfully establish. Rooks preferentially cache seeds in ploughed fields. Thus, land-use change combined with disperser changes can cause rapid increase of a non-native species, allowing it to become invasive. This may have cascading effects on the entire ecosystem. Thus, species that are non-native and not invasive can become invasive as habitats and dispersers change

Karbonatyzacja betonu: trwałość vs sekwestracja CO2

Karbonatyzacja betonu – chemiczna interakcja dwutlenku węgla i hydratów cementu zagrażająca ochronie zbrojenia przed korozją – jako proces nieunikniony w konstrukcjach z betonu w większości środowisk eksploatacyjnych, jest jednym z kluczowych czynników determinujących trwałość i stanowi kryterium projektowania materiałowego betonu i projektowania konstrukcyjnego elementów. Jednocześnie reakcja CO2 z wodorotlenkiem wapnia w betonie stanowi skuteczną formę sekwestracji dwutlenku węgla, korzystnie modyfikującą bilans CO2 w przyrodzie oraz zmniejszającą ślad węglowy cementu i betonu. W artykule rozważono oba aspekty karbonatyzacji, w kontekście poszukiwania bezpiecznej równowagi pomiędzy zapewnieniem wymaganej trwałości konstrukcji i wykorzystaniem potencjału sekwestracyjnego betonu, z uwzględnieniem pełnego cyklu życia cementu/betonu, w tym okresu porozbiórkowego. Przedstawiono także przykład takiego bilansu dla fragmentu hipotetycznej konstrukcji – wiaduktu drogowego.Concrete carbonation – the chemical interaction of carbon dioxide and cement hydrates threatening the protection of the reinforcement against corrosion – as an inevitable process in concrete structures in most exploitational environments, is one of the key factors determining durability and is a criterion for concrete design and structural design of elements. At the same time, the reaction of CO2 with calcium hydroxide in concrete is an effective form of carbon dioxide sequestration, favorably modifying the CO2 balance in nature and reducing the carbon footprint of cement and concrete. The article considers both aspects of carbonation in the context of the search for a safe balance between ensuring the required durability of the structure and the use of the sequestration potential of concrete, taking into account the full life cycle of the cement/concrete, including the post-demolition period. An example of such a balance is also presented for a fragment of a hypothetical structure - a road viaduct