In this paper we discuss the test results for concretes containing various amounts of ggbs as compared to concretes made with Portland cement. The main objective of these tests is to evaluate the influence of varying air content in such mixtures on the structure and frost resistance of concrete. The authors suggest that the approach presented here allows for a safe design of concrete mixtures in terms of their frost resistance.

The results indicate that concrete can be resistant to surface scaling even at the W/C ratio markedly higher than 0.45. Increased addition of ggbs leads to a decrease in concrete resistance to surface scaling. Proper air entrainment is the fundamental factor for frost-resistant concrete, and the air void system has to be assessed (micropore content A₃₀₀, spacing factor L). The addition of ggbs increases pore diameters, thus, to obtain the appropriate air pore spacing factor, micropore quantities introduced have to be increased.

This paper presents research results of composite tubes filled with self-compacting concrete. The impact of the selected materials and geometric factors on resistance to the vertical shear was evaluated in this study. The resistance of the tested members was compared with recommendations given in Eurocode PN-EN 1994-1-1. From the results obtained in the tests it can be deduced that more parameters should be taken into consideration when determining resistance to the vertical shear in the interface between steel and concrete than PN-EN 1994-1-1 recommends.

Thin-walled bars currently applied in metal construction engineering belong to a group of members, the cross-section resistance of which is affected by the phenomena of local or distortional stability loss. This results from the fact that the cross-section of such a bar consists of slender-plate elements. The study presents the method of calculating the resistance of the cross-section susceptible to local buckling which is based on the loss of stability of the weakest plate (wall). The "Critical Plate" (CP) was identified by comparing critical stress in cross-section component plates under a given stress condition. Then, the CP showing the lowest critical stress was modelled, depending on boundary conditions, as an internal or cantilever element elastically restrained in the restraining plate (RP). Longitudinal stress distribution was accounted for by means of a constant, linear or non-linear (acc. the second degree parabola) function. For the critical buckling stress, as calculated above, the local critical resistance of the cross-section was determined, which sets a limit on the validity of the Vlasov theory. In order to determine the design ultimate resistance of the cross-section, the effective width theory was applied, while taking into consideration the assumptions specified in the study. The application of the Critical Plate Method (CPM) was presented in the examples. Analytical calculation results were compared with selected experimental findings. lt was demonstrated that taking into consideration the CP elastic restraint and longitudinal stress variation results in a more accurate representation of thin-walled element behaviour in the engineering computational model

The objective of the presented paper is to investigate the performance of concrete containing volcanic scoria as cement replacement after 7, 28, 90, and 180 days curing. Five performance indicators have been studied. Compressive strength, water permeability, porosity, chloride penetrability, and reinforcement corrosion resistance have all been evaluated. Concrete specimens were produced with replacement levels ranging from 10 to 35%. Test results revealed that curing time had a large influence on all the examined performance indicators of scoria-based concrete. Water permeability, porosity, and chloride penetrability of scoria-based concrete mixes were much lower than that of plain concrete. Concretes produced with scoria-based binders also decelerated rebar corrosion, particularly after longer curing times. Furthermore, an estimation equation has been developed by the authors to predict the studied performance indicators, focusing on the curing time and the replacement level of volcanic scoria. SEM/EDX analysis has been reported as well.

Assessment of the flexural buckling resistance of bisymmetrical I-section beam-columns using FEM is widely discussed in the paper with regard to their imperfect model. The concept of equivalent geometric imperfections is applied in compliance with the so-called Eurocode’s general method. Various imperfection profiles are considered. The global effect of imperfections on the real compression members behaviour is illustrated by the comparison of imperfect beam-columns resistance and the resistance of their perfect counterparts. Numerous FEM simulations with regard to the stability behaviour of laterally and torsionally restrained steel structural elements of hot-rolled wide flange HEB section subjected to both compression and bending about the major or minor principal axes were performed. Geometrically and materially nonlinear analyses, GMNA for perfect structural elements and GMNIA for imperfect ones, preceded by LBA for the initial curvature evaluation of imperfect member configuration prior to loading were carried out. Numerical modelling and simulations were conducted with use of ABAQUS/Standard program. FEM results are compared with those obtained using the Eurocode’s interaction criteria of Method 1 and 2. Concluding remarks with regard to a necessity of equivalent imperfection profiles inclusion in modelling of the in-plane resistance of compression members are presented.

These joints are used when the designer and contractor anticipate difficulties during the construction of overlap joints. They were not included in the PN EN 1993‒1‒8 in full scale. Resistance assessment of such joints is presented in accordance with standard rules. The results were compared with the experimental studies carried out at the “Mostostal” Centre; while the former research activities and the legitimacy of the proposed method of assessing the resistance of these joints was confirmed. This is an example of an overlap joint calculation.

The paper presents the results of studies of hybrid composite layers Ni/Al2O3/Cgraphite produced by the electrodeposition method. Three variants of hybrid composite layers were prepared in electrolyte solutions with the same amounts of each dispersion phases which were equal to 0.25; 0.50 and 0.75 g/dm3. The structure of Ni/Al2O3/Cgraphite layers as well as the Al2O3 and graphite powders, which were used as dispersion phases was investigated. The results of morphology and surface topography of produced layers are presented. The modulus of elasticity and microhardness of the material of produced layers were determined by DSI method. Tribological and corrosion resistance tests of produced layers were carried out. Realized studies have shown that the material of the produced layers is characterized by a nanocrystalline structure. Incorporation of dispersion phases into the nickiel matrix increases the degree of surface development of layers. Ni/Al2O3/Cgraphite layers are characterized by high hardness and abrasion resistance by friction, furthermore, they provide good corrosion protection for the substrate material.

The cotton aphid, Aphis gossypii is an economically significant insect pest infesting various important crops and vegetables. The neonicotinoid, acetamiprid was recommended against aphids with excellent results. Resistance emergence and environmental pollution makes acetamiprid a favorable alternative to conventional insecticides. The aims of the present work were to predict acetamiprid resistance risk in A. gossypii, investigate cross resistance to other tested insecticides and explore acetamiprid stability in the absence of selection. A field-collected population from Sharqia governorate, Egypt was selected with acetamiprid. After 16 generations of selection, there was a 22.55-fold increase in LC50 and the realized heritability (h2) of resistance was 0.17. Projected rates of resistance indicated that, if h2 = 0.17 and 50% of the population was killed at each generation, then a tenfold increase in LC50 would be expected in 12.2 generations. If h2 was 0.27 then 7.63 generations would be needed to achieve the same level. In contrast, with h2 of 0.07 it necessitates about 30 generations of selection to reach the same level. Cross resistance studies exhibited that the selected strain showed obvious cross resistance to the other tested neonicotinoid members, moderate cross resistance to alpha-cypermethrin and no cross resistance to pymetrozine. Fortunately, resistance to acetamiprid in the cotton aphid was unstable and resistance reverses the nearby susceptible strain throughout five generations without exposure to acetamiprid. Our results exhibited cotton aphid potential to develop resistance to acetamiprid under continuous selection pressure. The instability of acetamiprid makes A. gossypii amenable to resistance management tactics such as rotation with pymetrozine.

 Widespread opinion holds that calcareous rocks have limited suitability for use in the production
 

 of aggregates and stone products having adequate frost resistance. However, some of the rocks, in
 

 particular those from earlier geological periods, provide a promising alternative to silicate rocks.
 

 The paper presents results of the analysis of Devonian carbonate rock originating from two selected
 

 mines in the Swietokrzyskie region. The examined mines extract limestone from two different
 

 deposits of the same age. The rock samples are collected from beds lying at different depths, distinct
 

 in texture and color in macroscopic examination. It was found that despite the changes in bulk density,
 

 porosity and absorption, all the examined samples were frost resistant.
 

 Using the Differential Analysis of Volumetric Strain method, the content of ice formed in the pore
 

 spaces was determined. In addition, the ratio of the content of water capable of freezing to the total
 

 pore volume, and the total amount of water absorbed due to capillary action in rock samples soaked
 

 in water, were analyzed. In all cases, it was revealed that the destructive action of freezing water was
 

 weakened due to a relatively low content of water capable of freezing and a substantial volume of
 

 pores that are not filled with water in capillary absorption.
 

 It is extremely important to be able to classify the available rock material. The generally adopted
 

 methods, including absorptivity tests, do not allow for precise categorization. In the investigations,

the authors focused on the analysis of the basic factors that are decisive for rock durability, including bulk density, pore filling level and volume absorption. The authors do not correspond compressive

strength and resistance to abrasion as this will be the subject of further research.

The aim of this study was to determine the effect of carfentrazone-ethyl (CE) doses of 0.265, 5.280, 10.560, 21.180, 42.240 μg kg-1 soil DM on fungi, Acnomycetes, organotrophic bacteria, total oligotrophic bacteria and spore-forming oligotrophic bacteria, and on the activity of dehydrogenases, catalase, urease, alkaline phosphatase, acid phosphatase, arylsulfatase and β-glucosidase. Carfentrazone-ethyl had a stimulating effect on total oligotrophic bacteria and organotrophic bacteria, but it inhibited the growth of Azotobacter, fungi, spore-forming oligotrophic bacteria and Actinomycetes. The analyzed substance modified the structure of soil microbial communities, and it induced the most profound changes in fungi. The highest values of the colony development (CD) index and the eco-physiological (EP) index were observed in organotrophic bacteria. The optimal dose of carfentrazone-ethyl stimulated the activity of dehydrogenases, catalase, urease, alkaline phosphatase, acid phosphatase and β-glucosidase, but it had no effect on arylsulfatase. The highest doses of the analyzed substance inhibited the activity of dehydrogenases (reduction from 11.835 to 11.381 μmol TPF), urease (reduction from 0.545 to 0.500 mmol N-NH4) and arylosulfatase (reduction from 0.210 to 0.168 mmol PNP). Dehydrogenases were most resistant to CE, whereas acid phosphatase and arylsulfatase were least resistant to the analyzed compound

In four years’ experiment the infestation of hazel nuts by hazelnut weevil was investigated. Significant differences in resistance of different hazelnut cultivars were found. Olbrzymi z Halle cultivar exhibited a moderate resistance to the pest and was classified to the III class, while other cultivars showed a moderate susceptibility to the pest and were classified to class IV.

The study was aimed at evaluating microbial contamination on the premises of the sewage treatment plant by determining the concentrations of selected groups of airborne microorganisms. Another objective was to determine the antibiotic sensitivity patterns of isolated strains of staphylococci. The research was conducted in a seasonal cycle, by the impaction method using Merck MAS-100 air sampler. Samples were collected at six sites, each representing a different stage of sewage treatment. The susceptibility of isolated staphylococci was assessed with the disc-diffusion method, following the recommendations of the EUCAST. The results indicate that the microbial population in the air of the investigated area was dominated by mold fungi, whose highest average concentration was recorded at site IV located near the final clarifier (7672 CFU•m-3). Heterotrophic bacteria and mannitol-positive staphylococci were the most numerous at locations where sewage undergoes primary treatment. In each subseuqent stage the number of microorganisms emitted into the air from the sewage was lower. Antibiograms show that more than 50% of Staphylococcus spp. exhibited resistance to penicillin and 20% to rifampicin. In addition, 90% of the analyzed strains were sensitive to other antibiotics. The fungal community included the following genera: Cladosporium, Fusarium, Alternaria, Penicillium, Aspergillus, Aureobasidium, and Acremonium.The highest air contamination with all studied groups of microorganisms was recorded at the locations where mechanical sewage treatment was performed. During the subsequent stages lower numbers of heterotrophic bacteria were emitted into the air. The air in the investigated sewage treatment plant did not contain multidrug-resistant staphylococci.

The Ti15Mo alloy has been studied towards long-term corrosion performance in saline solution at 37°C using electrochemical impedance spectroscopy. The physical and chemical characterization of the material were also investigated. The as-received Ti15Mo alloy exhibits a single β-phase structure. The thickness of single-layer structured oxide presented on its surface is ~4 nm. Impedance measurements revealed that the Ti15Mo alloy is characterized by spontaneous passivation in the solution containing chloride ions and formation of a double-layer structured oxide composed of a dense interlayer being the barrier layer against corrosion and porous outer layer. The thickness of this oxide layer, estimated based on the impedance data increases up to ~6 nm during 78 days of exposure. The observed fall in value of the log|Z|f = 0.01 Hz indicates a decrease in pitting corrosion resistance of Ti15Mo alloy in saline solution along with the immersion time. The detailed EIS study on the kinetics and mechanism of corrosion process and the capacitive behavior of the Ti15Mo electrode | passive layer | saline solution system was based on the concept of equivalent electrical circuit with respect to the physical meaning of the applied circuit elements. Potentiodynamic studies up to 9 V vs. SCE and SEM analysis show no presence of pitting corrosion what indicates that the Ti15Mo alloy is promising biomaterial to long-term medical applications.

The publication presents the results of examination of selected carburizers used for cast iron production with respect to their electric

resistance. Both the synthetic graphite carburizers and petroleum coke (petcoke) carburizers of various chemical composition were

compared. The relationships between electrical resistance of tested carburizers and their quality were found. The graphite carburizers

exhibited much better conductivity than the petcoke ones. Resistance characteristics were different for the different types of carburizers.

The measurements were performed according to the authors’ own method based on recording the electric current flow through the

compressed samples. The samples of the specified diameter were put under pressure of the gradually increased value (10, 20, 50, 60, and

finally 70 bar), each time the corresponding value of electric resistance being measured with a gauge of high accuracy, equal to 0.1μΩ.

The higher pressure values resulted in the lower values of resistance. The relation between both the thermal conductance and the electrical

conductance (or the resistance) is well known and mentioned in the professional literature. The results were analysed and presented both in

tabular and, additionally, in graphic form.