Crack Control Theory and Methods of the Mass Concrete Foundation in Nuclear Power Plants

The mass reinforced concrete in the raft foundation of nuclear power plant reactors has the characteristics of large area, large thickness, high strength, large cement dosage, and increased adiabatic temperature during construction, so the measures to prevent and control cracks are the top priorities. The internal stress is mainly the comprehensive stress caused by temperatures, hydration shrinkage and its constraints during construction. The temperature stress formula shows that the temperature field mainly varies along the radial direction, maximum temperature stress is horizontally hooped at the raft edge, independent of the temperature values and radius. Experimental data showed that the shrinkage stress was tensioned at the center and compressed at the edges, as opposed to the temperature stress. Based on this, the dynamic curing method was proposed, the temperature distribution was changed by continuously changing the insulation measures of the surface covering, and then the temperature deformation was used to neutralize the shrinkage deformation, the total deformation was tested by the elastic deformation device, and the cracks were controlled according to the third failure criterion, thus, and the total internal stress was controlled within a certain range. The crack control method is safe, economical, effective and low investment, and has been successfully applied in dozens of nuclear power foundation construction, which greatly shortens the foundation construction time.