Hybrid reinforced concrete with controlled volume deformations for hydrotechnical facilities
The development of hydration processes in cement concrete is associated with the release of significant amounts of heat, which leads to a significant exothermic temperature increasing in the concrete body, especially valid for massive structures. This creates a temperature gradient from the inside of the array to the surface. The latter may be re lated to the development of unacceptable internal stresses, often leading to cracking, defects and reducing the durability of the facility. The report presents the individual stages of the search for an optimal technical solution for the construction of a specific hydro-technical facility – a massive hybrid reinforced trapezoidal wall of a water catchment gorge, in the area of Stara Zagora town. In the context of specified geometric dimensions of the facility, the specific features of the exothermic increase of the temperature in the concrete body as a function of the hydration processes are discussed. A reasonable choice of a specific type of cement is proposed in order to limit the amount of heat released – slag cement CEM III-A 42.5 N with a specific heat of hydration up to 280 J/g. A specific concrete mix design has been proposed, providing a balanced increase in temperature within acceptable limits, preventing cracking, in two possible scenarios – winter and summer outdoor temperature conditions. An additional advantage of the mix is the inclusion in the recipe of fiber-reinforcement and high-tech chemical admixtures – deep internal crystallization and shrinkage-compensating one. Specific calculation data for the kinetics of temperature increasing are presented, and the obtained values are critically evaluated in terms of guaranteed cracks eliminating in the structure.