The paper presents the results of testing the bearing resistance of the bolted joints of thin-walled profiles used in modular construction. The two types of joints currently applied in the construction industry were subjected to tests. One of them served as the reference sample, and the other as the research sample, which was used to find a solution that is more favorable in terms of the complexity of its production process and its bearing resistance. In addition to the modified shape of the end-plates, the bearing resistance of the joint was also analyzed with regards to the different diameters of bolts (bolts M12 and M16 were used), their classes (the difference between bolts of class 8.8 and 10.9 was examined), and also the number of them in the joint (3 or 5 bolts). Moreover, two thicknesses of steel sheets (3 mm and 4 mm), from which thin-walled cold-bent profiles were made, were used in the research. The bearing resistance tests were carried out with the use of a testing press of the authors’ own design. On the basis of the measurements, plots of the dependence between the deflection of the samples and the force acting in the middle of their span were drawn. It was shown that the tested profile joint had an increased bearing resistance by up to 26% when compared to the reference sample. The maximum destructive bending moment M was equal to 10.7 kN·m for the reference sample, and to 13.5 kN·m for the analyzed design solution. In total, 6 types of modified joints were made for the tests, of which five showed a comparable or higher bearing resistance than the reference sample. Each type of joint was tested by bending it in two directions in relation to the central axis of its cross-section.

The paper presents the effect of a viscosity modifying admixture (VMA) on the air permeability, sorptivity and strength parameters (compressive and tensile strength) of concrete. The Atlas VM-500 admixture used in the research is a well-known additive that is commonly applied in concrete technology. Air permeability tests were carried out using the Torrent method. It was found that viscosity modifying admixtures (VMAs) have a significant impact on the permeability of concrete. The lowest values of the ���� coefficient were obtained for specimens that matured in a water environment, and which contained 0.5% of VMA. This amount of additive reduced permeability by 34% when compared to the reference series of concrete. For air-conditioned specimens with 1.2% of VMA, the maximum decrease was 28% when compared to the reference samples. In the case of samples conditioned in an environment with an increased humidity, the maximum decrease occurred with a lower VMA content of 0.5% and amounted to 27% when compared to the reference samples. In addition, it was shown that the addition of 1.2% of VMA improved the compressive strength of concrete by 2.3% during its curing in water. In turn, this amount of VMA deteriorated its strength by 10.4% when the specimens were conditioned in air, and by 8.1% when they were conditioned in high humidity.

The work presents results of research on the influence of micro materials on the thermal conductivity λ of gypsum. In the research, cellulose-based polymer and aerogel were used as the modifying micro materials. For the purpose of measuring the thermal conductivity, a non-stationary method was used based on the “hot wire method”. A very precise set of devices for measuring and recording the temperature of the heating wire was used. In the presented solution, a single measurement took only one minute. Measurements were recorded with the help of a computer measuring system, with a sampling time of 0.01s. During the 60-second-long test, 6000 measurements of the heating wire temperature were collected. A decrease of the thermal conductivity and density of hardened gypsum with added micro materials was observed due to modifications of the structure of the final product. Experimental values of the thermal conductivity of the gypsum specimens with the addition of polymer and aerogel were respectively over 23% and 6% lower than the non-modified gypsum specimen.