The paper presents results of investigations of compressive strength and shrinkage of concrete samples made on the basis of the Portland cement CEM I 32.5R, after 2, 7, 14, 28, 90, and 365 days of maturation in four different maturation conditions. It was shown that after 28 days the samples cured according to the standard in the cuvettes with water achieved the highest compressive strength, although the early-age compressive strengths after 7 and 14 days were lower than those for the samples cured in building film and in dry conditions. A determined correlation between the compressive strength and shrinkage of the concrete proves that wet curing also allows a total elimination of the shrinkage in the first 28 days. Along with the growth of the compressive strength, the drying shrinkage reduces. Obtained results confirmed that the best way of concrete curing, among the analyzed methods, from the point of view of both compressive strength and volume changes is the wet curing.

Concrete is a highly alkaline material; therefore, the presence of organic acids (acetic, butyric, lactic) from agricultural sewage constitutes a threat to the concrete and the environment. The investigations were aimed at simulating the influence of highly concentrated organic acids on concrete elements of livestock buildings. Cubic samples 100 × 100 × 100 mm of the ordinary concrete were immersed in 10% acetic acid for 270 days. Then, the compressive strength and mass decrement of the samples were determined as well as using SEM images and a 3D-profilograph to profile the surface roughness and depth of changes evoked in the structure of the samples by penetrating acid. The results were compared with those for a control sample (not subjected to the effects of aggressive agents) as well as for samples placed in a neutral and alkaline environment. The compressive strength of the samples stored in the acidic environment was 22.23% lower than that of the control sample, whereas the compressive strength of those samples stored in an alkaline environment were 44.27% higher. Conclusions from these investigations can be of innovative importance in the preparation of environmental impact reports, which are necessary for obtaining permission for the construction and use of livestock buildings, and afterward in the reduction of the impact of these buildings on the environment and surface and underground water resources.

No abstract

Contact of concrete with aggressive factors, technological structures, reduces their durability through microstructural changes. This work presents the results of research on determining the influence of post grit chamber sewage and sewage from the active sludge chamber in three different environments, i.e., acidic, neutral, and alkaline, on the structure and compressive strength of concrete. Compressive strength tests were carried out after 11.5 months of concrete cubes being submerged in the solutions and compared. To complete the studies, the photos of the microstructure were done. This made it possible to accentuate the relationship between the microstructure and performance characteristics of concrete. The time of storing the cubes in both acidic environments (sewage from post grit chamber and active sludge chamber) has a negative influence on their compressive strength. The compressive strength of cubes decreases along with the time. Compressive strength of cubes increases with increasing pH of the environment.

The paper discusses the principles of terraces design assessment with different types of insulation. It presents and compares layer systems and choice of materials in the existing terraces and modernized. Special attention was paid to the need to ensure adequate thermal insulation in areas adjacent to the balconies and terraces as well as terraces. See also the main principles of good design such structures, taking into account issues of temperature and humidity, as well as making the modernization of the terraces. * Corresponding author: marek_dohojda@sggw.pl

Increasing urban populations raises a number of problems and risks that are strengthened by observed and projected climate change. An increase in green areas (so-called green infrastructure) has turned out to be an effective means of lowering temperature in the city. Green roofs can be one of the possible measures leading to achieving this aim. The aim of the study was the analysis of temperature changes of different roof surfaces (conventional roof, board, intensive roof substrate without plant cover, substrate covered with plants (shrubs). Studies on comparing the temperature between a conventional roof and green roofs were carried out in the period from April to September 2015 on the roof of the building of the Faculty of Modern Languages, University of Warsaw. The measurement was performed using the FLIR SC620 thermal imaging system. As a result of the tests, it was found that in the summer months the differences between the temperature of the green roof and the conventional roof amounted to a maximum of 31.3°C. The obtained results showed that the roof with vegetation can signifi cantly contribute to the mitigation of the urban heat island phenomenon in urban areas during summer periods.

No abstract

This paper aims to present the results of compressive strength tests of concrete specimens, prepared according to two recipes, after 2, 7 and 28 days of maturing in four different environments. The concrete specimens had the same w/c ratio, the same amount of aggregate of particular fractions, the addition of a superplasticizer, but they differed in the cement type. In one recipe, the Portland cement CEM I 32.5R was used, in the other – pozzolanic ash cement CEM IV/B(V) 32.5R-LH/NA. Concrete specimens with dimensions of 100 x 100 x 100 mm made according to both recipes were placed in individual ripening environments: in cuvettes with water, soaked and wrapped with construction foil, left in room conditions in the laboratory, placed outside the laboratory and being exposed to the atmospheric conditions. The obtained compressive strength results confirmed that the best way of curing concrete is the wet cure (in cuvettes with water). It has been proven that the choice of proper curing method is key in terms of compressive strength.