Evaluation of the effectiveness of mineral additives in cement systems in the development of "core - shell" photocatalytic compositions

Introduction. Creation of highly efficient photocatalysts for construction composites, which are characterized by increased activity and an extended spectral range of action, is a very important area of research. It is known that "core (substrate) -shell (photocatalyst)" compositions, where mineral raw materials of various genesis can act as carriers, are one of the most effective types of photocatalytic additives for cement systems. It is worth noting that for integrated assessment of the substrate efficiency, we need to obtain information on the composition and properties of raw materials used among which its chemical activity and structure-forming role in cement systems are of paramount importance. The purposes of this study are (1) to establish the influence pattern of four types of mineral additives (silica fume, metakaolin, expanding sulfoaluminate modifier and microcalcite) on the structure formation processes of plasticized cement systems and (2) to identify the most effective modifiers for further use as mineral substrates in the photocatalytic compositions. Methods and materials. Specific surface area and granulometric composition of mineral modifiers were determined by the Kozeny-Karman and laser diffraction methods. The phase composition of mineral additives and modified cement systems were studied using X-ray diffraction phase analysis. Results and discussion. Features of mineralogical and granulometric compositions of mineral additives were revealed. It was determined that the use of individual and complex mineral additives based on silica fume, metakaolin and ESAM made it possible to directionally influence on content of the main phases of cement stone such as ettringite, portlandite, calcium hydrosilicates of different basicity. Conclusions. The increased chemical activity of these modifiers in cement systems, due to presence of reactive minerals in the structure, along with features of the granulometric composition (high dispersity and narrow particle size distribution), indicated the potential prospects for their use as mineral substrate in "core - shell" photocatalytic compositions.