## 1 Introduction  
In recent years, there has been a growing interest in the possibility of using nanometric materials as a potential additive for the production of cement composites [1]. This is mainly due to the unique properties of nanoparticles, such as their large specific surface area and chemical activity [2]. Until now, attempts have been made to determine the effect of some nanoparticles on the selected physical and mechanical properties of cement composites obtained with their use. Research included the influence of nanoparticles on the following concrete parameters: porosity [3], water absorption [4], compressive strength [5], bending strength [6], and the destruction process [7]. In the literature, however, in the case of concretes made with the addition of nanoparticles, there is no research concerning mechanical parameters related to rheology, such as creep. Knowledge of the creep effect and of the possibility of its conscious control is important with regard to the durability and maintenance of objects made of concrete [8]. As a rule, when assessing the creep of concrete at the macro-scale, this material is treated as homogeneous, consisting mainly of aggregates. The standard methods that are used for such materials to determine concrete creep are time- and labor-consuming [9]. However, it has been proved that the effective mechanical parameters of concrete are significantly affected by the properties of the structure of the cement matrix observedat micro and nano levels [10], which should be assessed using appropriate techniques. One such technique is the indentation method. Indentation is a method for measuring the mechanical properties of a material. This method is based on pressing a hard indenter in the form of, e.g., a diamond pyramid (Berkovich indenter) into a sample. Indentation research can be carried out at several levels of observation, from macro, to micro and to nano. The value of force applied to the surface of the sample being tested and the corresponding size of the obtained imprint, are directly related to the volume of the material subjected to the test. In the process of indentation, three stages can be distinguished: loading--the indenter is pressed into the material at a given speed until reaching the assumed force, which depends on the type of material; retaining the indenter in the material for a specified period of time; and unloading--usually at the same speed at which the indenter was pressed. The possibility of continuous monitoring of the indentation process enables the following material parameters to be determined: hardness \(\mu H\), observed at micro-scale, and the indentation module \(\mu E\)[11]. It also allows rheological parameters such as creep [12] or relaxation [13] to be calculated. When determining the creep of a cement matrix using the indentation method, which is a form of microstructural analysis, it is necessary to take into account several factors that affect the obtained results [14]. They include the preparation of the samples, the oxidation of the tested surface, the friction and adhesion of the indenter tip, the roughness of the tested surface, the surface of the imprint, and also the development of displacements. Particular attention should also be paid to the time of loading and unloading increase, the time of constant loading, and the number of loading and unloading cycles [14]. It is also worth noting that the assessment of creep using the method of indentation correlates well with the macroscopic assessment and also significantly accelerates the time of the study [15]. So far, many studies have concerned the subject of creep in ordinary, high-performance and self-compacting concrete (SCC). In a paper [16], it was proved that creep is greatly reduced by the use of ultrafine ground granulated blast-furnace slag (GGBS) and silica fume (SF). In addition, a reduction of creep by even more than 50% can be expected when the fly ash replacement level is increased from 35% to 60% [17].