The effect of different composition sols on change of structure and properties of cement stone

One of the most rapidly developing directions in science of structural materials is the application of nanotechnology for development of new generation concrete. To date, nanodispersed additives were widely used in technology of concrete, because they allow increasing its main physical-mechanical properties. The use of effective additives contained nanoparticles in its composition allows to optimize structure of concrete, and also to reduce a consumption of the most expensive component - cement. The need to make new available and rather inexpensive modifiers of cement and concrete products is due to the resource intensive, difficulty of its receiving, therefore, high cost and, respectively, a market price. The article discusses the production of additives in the form of sols on the basis of the chemical elements of VI group of the periodic system of D.I. Mendeleev, in particular of sulfur and chromium, and its use for modification of cement stone. The main characteristics of aqueous solutions of sols were defined by physical and chemical methods of researches and calculation. The content of the colloid additives in cement stone was optimized as a result of the conducted experimental studies, it was determined that the kinetics of cement strength setting depends on the type and amount of sols. The content of sols in cement stone is about thousand fractions of binder mass, i.e. its strength increases at the microlevel. That gives significant saving of the presented additives when they are introduced into cement and concrete compositions. The use of additives of sols on the basis of compounds of sulfur and chromium not only accelerated hydration and hardening of cement in the early period, but also significantly improved the strength characteristics of cement stone. The received nanodispersed additives can be included in group of hardening-accelerating admixes of cement. The increasing of strength of a cement stone modified by sols of various compositions is a result of change of its structure. Electronic and microscopic analysis showed that use of sols of different composition as modifiers leads to compaction of microstructure of cement stone and formation of difficult compounds of sulfur and chromium with hydrated calcium silicates.