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 mu m.