The proper design of protective structures may start from improving the characteristics of soils. In order to obtain reasonable safety criteria, several research studies have recently been dedicated to enhancing complex civil engineering structural systems with the use of nanotechnology. Thus, the following paper investigates the effect of nanospheres, including nanosilica (nano‐SiO₂) and nano zinc oxide (nano‐ZnO), on lime‐stabilized high‐plasticity clay soil. For this purpose, unconfined compressive strength (UCS) and California bearing ratio (CBR) tests were performed on samples. The results showed that the use of the selected nanospheres greatly increased the UCS of the samples compared to untreated soil. The UCS value of samples containing 6% lime and 1.5% nano‐ZnO after 28 days of treatment increased by 5‐fold compared to the UCS of untreated samples. In addition, the samples containing 6% lime and 2% nano‐SiO₂, with similar curing conditions, experienced a 5.3‐fold increase in their UCS value compared to the untreated samples. These compounds were considered as the optimal amounts and showed the highest mechanical strength in both UCS and CBR tests. The same trend was achieved in the CBR test, in which the CBR value for the optimal mixtures containing nano‐ZnO and nano‐SiO₂ was 14.8 and 16.6 times higher than that of high‐plasticity clay soil, respectively. Finally, the results obtained from scanning electron microscopy (SEM) analysis revealed that the nanospheres caused a dense and compact matrix to form in the soil, which led to the enhancement of the mechanical strength of the treated samples.

Non-destructive testing (NDT) and semi-destructive testing (SDT) have recently been more frequently used for the evaluation and condition assessment of concrete floors in various types of buildings. The subject of the article is to briefly introduce the reader to the problem of adhesion between overlays and substrates in concrete floors and to illustrate the current state of knowledge on the subject. The aim of this paper was to briefly describe the recently used non-destructive and semi-destructive testing methods and the parameters useful for characterizing the adhesion between overlays and substrates in concrete floors, as well as the methods useful to characterize the functional properties of the overlays. A recent literature survey, related to the adhesion between the overlays and substrates in concrete floors, is thus shown. Special emphasis was placed on the critical review of the current research results. Based on the analysis of the literature review, research gaps have been presented in order to highlight future research directions.

In civil engineering, overlays should have appropriate strength and functional parameters. In order to obtain these parameters to the desired level, additional actions are applied in the form of dispersed reinforcement, surface hardening and impregnation. There is a lack of detailed results of studies on the impact of amorphous SiO₂ nanospheres contained in the cement mortar of the overlay in concrete floors on its bonding with the concrete substrate, as well as on its functional parameters. Considering the above, the article presents the results of research regarding the impact of amorphous SiO₂ nanospheres. It was also shown that the most favourable results (understood as lower abrasion resistance, higher subsurface tensile strength and a higher overlay hardness), when compared to the reference mortar, are achieved with the use of amorphous SiO₂ nanospheres in an amount of 0.5% in relation to the cement mass. This is confirmed by studies carried out using scanning electron microscopy, which confirmed that these improvements are due to the fact that the mortar with the addition of amorphous SiO₂ nanospheres in an amount of 0.5% of the cement mass is characterized by a lower ratio of pores within the range from 0.83 to 7.50 μm.

This article focuses on the development of nanoalumina-based cement mortars for overlay applications in concrete floors. It focuses on the effect of applying aluminum oxide (Al₂O₃) nanopowder to the cement mortar used to make the overlay, on the adhesion of this overlay to concrete substrate and on its functional properties. It was claimed that the addition of 0.5% of Al₂O₃ nanopowder has a positive effect on the adhesion of the cement mortar used to make the overlay to the substrate made of concrete. The prior studies performed using scanning electron microscopy (SEM) confirmed that the reason for the improvement in adhesion is the fact that cement mortar used to make the overlay with the addition of 0.5% of Al₂O₃ nanopowder is less porous than the reference mortar within the interphase. The article concurs that the most favorable results, in terms of lower abrasion resistance and higher subsurface tensile strength of the cement mortar used to make the overlay, are mainly brought about by adding 0.5% of Al₂O₃ nanopowder.

In this study the results of research that focused on abrasion resistance of concrete containing selected mineral powders are presented. The influence of replacing part of the cement on the physical properties of concrete was studied in the article. The concrete mixtures were modified by addition of basalt, quartz and quartz-feldspar powders in amount of 10, 20 and 30% of the weight of the cement. The results showed that using mineral powders can reduce or increase concrete surface abrasion resistance depending on the type of mineral powder and its concentration in concrete mixture

Recently, the research of innovative building materials is focused on applying supplementary materials in the form of micro- and nanopowders in cementitious composites due to the growing insistence on sustainable development. Considering above, in paper, a research on the effect of microsilica and SiO₂ nanoparticles addition to cement paste, designed with Andreasen and Andersen (AA) packing density model (PDM), in terms of its physical and mechanical properties was conducted. Density, porosity, compressive strength, hardness, and modulus of indentation were investigated and compared regarding different amount of additives used in cement paste mixes. Microstructure of the obtained pastes was analyzed. The possibility of negative influence of alkali-silica reaction (ASR) on the mechanical properties of the obtained composites was analyzed. The results of the conducted investigations were discussed, and conclusions, also practical, were presented. The obtained results confirmed that the applied PDM may be an effective tool in cement paste design, when low porosity of prepared composite is required. On the other hand, the application of AA model did not bring satisfactory results of mechanical performance as expected, what was related, as shown by SEM imaging, with inhomogeneous dispersion of microsilica, and creation of agglomerates acting as reactive aggregates, what as a consequence caused ASR reaction, crack occurrence and lowered mechanical properties. Finally, the study found that the use of about 7.5% wt. of microsilica is the optimum in regards to obtain low porosity, while, to achieve improved mechanical properties, the use of 4 wt. % of microsilica seems to be optimal, in the case of tested cement pastes.