This article presents the effect of aluminum nanoxide on the physical, strength and structural properties of cement mortars. The mortars were made with a water to binder ratio of 0.5 and a binder to sand ratio of 1:3; and 1%, 2%, 3% and 4% of aluminum nanoxide, respectively, were used by cement weight. First, the consistency of nano-Al₂O₃ mortars was tested. Next, after 7 days of sample maturation, compressive and flexural strength tests were carried out and continued after 28 and 90 days of the maturing of the mortars. The best test results were obtained for mortars with the addition of 1% aluminum nanoxide, the compressive strength of which increased by about 20% compared to the reference mortars. The water absorption and rising capillary tests as well as SEM observations were also performed. Another aim of the article is the analysis of the fracture morphology of nano-Al₂O₃ modified mortars. It is assumed that a change of the microstructure of the hardened cement paste affects not only the properties of the modified mortars but also the roughness of the fractures formed as a result of the destruction of the surface. Roughness analysis was performed with methods and tools relevant to fractal geometry. The fractographic analysis showed a significant influence of the modifier in the form of nano-Al₂O₃ on the values of fractal dimensions. The lowest values of the fractal dimension D and the fractal dimension of the D_RP roughness profile of the fracture surface profile lines were obtained for nano-Al₂O₃ modified mortars. The conducted research proved the fractal dimension to be a parameter extremely sensitive to modifications of mortar composition as well as changes related to the maturation time.

The article presents changes in the quality of tap water depending on time spent in installation and its impact on the creation of biofilms on various materials (polyethylene (PE), polyvinyl chloride (PVC), chrome-nickel steel and galvanized steel). For the first time, quantitative analyses of biofilm were performed using methods such as: Adenosine 5’-triphosphate (ATP) measurement, flow cytometry, heterotrophic plate count and using fractographical parameters. In the water, after leaving the experimental installation, the increase of turbidity, content of organic compounds, nitrites and nitrates was found, as well as the decrease in the content of chlorine compounds, dissolved oxygen and phosphorus compounds. There was an increase in the number of mesophilic and psychrophilic bacteria. In addition, the presence of Escherichia coli was also found. The analysis of the quantitative determination of microorganisms in a biofilm indicates that galvanized steel is the most susceptible material for the adhesion of microorganisms. These results were also confirmed by the analysis of the biofilm morphology. The roughness profile, the thickness of the biofilm layer can be estimated at about 300 μm on galvanized steel.

The article presents the results of examination of the fractal dimension D of macro-pores in concrete. The concretes were made from coarse basalt aggregate. Fractal examinations showed that the fractal dimension D of macro-pores in concrete was different, depending on the water-cement ratio W/C. The performed examination of macro-pores in concretes has shown the existence of a statistically significant correlation between the fractal dimension DBC, as determined by the box method, the relative number of pore crosssections NA (or the number of pores N) and the total air content A, as well as between the fractal dimension DBC, the relative number of pore cross-sections NA and the water-cement ratio W/C.

The article shows the effectiveness of the use of polymer additives for the production of fine-grained concrete mixtures and concretes based on using coal fly ash, which can be used as working mixtures for a 3D printer. Using mathematical planning of experiments, a set of experimental–statistical models was obtained that describes the influence of mixture composition factors including copolymer additive on the most important properties of ash-containing concrete mixtures and concretes for 3D concrete printing in the presence of a hardening accelerator additive. It is shown that when the dry mixture is mixed in water, the redispersed polymer powders are converted into an adhesive polymer dispersion, which, when the solution cures, creates “rubber bridges” in its pores and at the border with the base. They have high tensile strength and elastically reinforce the cement stone; in addition, they are also capable of not only significantly increasing the adhesion between the layers of the extruded mixture, but also significantly smoothing out such shortcomings of the cement stone as increased brittleness, low ultimate elongation, and a tendency to cracking.

Modern methods of designing and testing concrete must be extended to appropriate material engineering approaches. It is then crucial to link the properties of concrete with its structure described in a quantitative way. The aim of the article was to present the results of research on concretes modified with three additives: Silica fume (SF), activated fluidal ash (FA), and metakaolinite (MK). The concretes were tested for compressive strength, fracture toughness (determining critical stress intensity factor K_Ic^S and elastic modulus E). Also, stereological and fractal tests were performed. The research program covered three separate experiment plans, adopting the water/binder ratio and the additive/binder mass ratio as the independent variables. The results of experiments and their analysis proved a statistically significant relationship between fracture morphology (fractal dimension D) and concrete composition and fracture toughness. A higher fractal dimension was found in concretes with a higher content of cement paste and a lower content of additive. No significant effect of the type of additive used in the above dependence was found. An original method enabling the determination of mechanical properties of concrete with no need for destructive testing has been developed.