Complex mechanical-thermal synthesis of nanostructured calcium hydrosilicates for cement composites

Introduction. The use of nanosized calcium hydrosilicates as additives accelerating the structure formation of cement compositions is becoming increasingly popular. The reason for this lies in their high efficiency as accelerators in the absence of a negative effect on the long-term strength and durability of cement composites. An additional advantage of nanoscale calcium hydrosilicates is the variety of existing methods for their synthesis, among which the mechanochemical method stands out due to the availability of raw materials and the simplicity of the technical design of the synthesis. Article body. The review considers a new method for the synthesis of nanostructured calcium hydrosilicates – complex mechanical-thermal synthesis, which is a combination of mechanochemical synthesis of carbohydrate-modified calcium hydrosilicates with their subsequent thermal decomposition. Modified calcium hydrosilicates , in the interlayer space of which the carbohydrate is intercalated , are capable of decomposition under conditions of low-temperature thermolysis (<150 oC ) with the formation of hydrosilicate nanoparticles, the coagulation of which leads to the formation of a nanostructured phase of calcium hydrosilicates – xerogel. A mixture of xerogel with residues of raw materials, hydrated phases that have not decomposed during thermolysis is a calcium silicate dispersion (CSD). The technological features of CSD synthesis and some properties of CSD are described. In particular, a moderate (up to 60%) acceleration of daily strength gain of CSD-modified cement mortars with a parallel increase in grade strength (17%) is revealed. A significant effect of CSD on the rheological properties of cement mixtures is noted. Conclusion. Complex mechanical-thermal synthesis is a new synthetic direction for obtaining nanosized calcium hydrosilicates. The development of this direction is far from complete and is closely related to the development of the theoretical base, in particular, the concept of non-classical nucleation as applied to hydrosilicate phases. The development of the method can be aimed at searching for new organic modifiers with the acquisition of new properties of modified hydrosilicates and products of their thermal decomposition, at improving synthesis modes in order to regulate the quantitative and qualitative parameters of the nanostructured phase, consumer properties of the CSD, and expanding the scope of its application.