Cracking Control of Mass Concrete Slab in Nuclear Power Plant with Dynamic Curing

To control cracking of mass concrete slabs in nuclear power plants (NPPs), a dynamic curing technique is proposed based on the stress superposition principle and elastic assumptions. It optimizes the stress field through targeted regulation of temperature variation according to the measured elastic strain epsilon(em) by flexible application of surface-protection techniques. The limit tensile strain of epsilon(em) is defined as 120 mu epsilon to guarantee no cracks would occur. In its application on two slabs, only one hairline vertical crack was observed when eem reached 130 mu epsilon on the 12th day after casting. However, the tensile strain gradually decreased, and the crack tended to close with age. The presented technique has been verified on more than 20 NPPs throughout the continuous casting stage (and even the operation period), saving construction time in the meantime. In addition, it provides theoretical and technical guidance for further investigation of mass concrete with complicated cross-section shapes.