The long-term preservation and the future-oriented development of the infrastructure are of utmost importance for every country in the world. An increasing failure of infrastructure underpins a tremendous need for action. The reasons for this unsatisfactory situation are various, but certainly among them is often an insufficient performance of the building materials. This holds particularly true for reinforced concrete and its additives, which are nowadays commonly developed by empirical research. Almost all shortcomings of concrete durability are related to the transport of detrimental substances into the pore system. In this regard, a promising approach to prevent chemical deterioration processes is a functionalisation of the pore system by means of organosilicon-based surface treatments in order to hamper the uptake of aggressive aqueous solutions. However, little is known about the reaction mechanisms and the nature of the reaction products associated with such measures. However, this is necessary to obtain reliable information about their performance and ideally to develop these technologies further in a more target-oriented manner. ... mehrThe insufficient understanding of these processes has its origins in the inability of investigations of the reaction course of silicon organic compounds in the pore structure of cement-based systems and their underlying physical and chemical principles. This applies in particular to film-forming reactions in alkaline environments of the pore structure, which lead to functionalization (e.g. hydrophobic effect). The approach of this study is therefore to investigate the reaction products in model systems using mass spectrometry and to explain the course of the reaction by means of computational chemistry. In this way, reaction products of different reaction steps of the condensation of specific components into larger oligomers were characterized and the reaction sequence was explained by molecular modelling. These results contribute to a deeper understanding of the reactions and types of reaction products of organosilicon compounds used to improve the properties of cement-bound materials. This promotes further steps towards the performance-oriented development of such surface protection technologies.