High Performance Concrete for Containment Structures

摘要

Primary and secondary containment structures are the major components of the nuclear power plant (NPP). The primaryand secondary containment structures are mainly composed of prestressed concrete vertical cylindrical shell wall andsegmented hemispherical dome with openings. The performance requirements of the concrete of containment structures aremainly radiological protection, structural integrity, controlled deformation, leak tightness, durability etc. For this highperformance concrete (HPC) with special attributes such as moderate compressive strength, low shrinkage and highdurability are essential. Department of Civil Engineering, Jadavpur University, India had undertaken a project on thedevelopment of such HPC suitable for containment structure with financial and technical support from Department of AtomicEnergy, Govt. of India. In the project, HPC was developed using Indian ordinary portland cement (a relatively low-aliteportland cement compared to ASTM Type I and other equivalent normal cements), locally available aggregates, silica fumeand ASTM Type F and G superplasticizers. After several trials a high initial slump of 180 to 200 mm and 30-min. slump of150 to 170 mm was achieved with a water-cementitious material ratio of 0.32. The mix was cohesive, consistent and freefrom bleeding and segregation. The maximum compressive strength of 72 MPa, split tensile strength of 4.52MPa and flexuraIstrength of 6.7 MPa was achieved after several trials. The HPC with reasonably low absorption value and drying shrinkagewas obtained for the mixtures containing silica fume of 7.5 % and above. Though the concretes with silica fume content 7.5,10 and 12.5 % were acceptable from workability, strength, shrinkage and absorption point of view, the concrete with silicafume greater with 12.5 and 15 % showed more strength-loss than the other mixtures in 10% MgSO_4 and 1% H_2SO_4 acidsolutions in spite of having a better pore size distribution (measured by mercury porosimetry). X-ray diffraction of samplesexposed in acid and sulfate solutions revealed that the attack was possibly more chemical than physical in nature and gelstructure was particularly attacked. The within-batch variation of compressive strength of some selected types shows thatHPC developed in the laboratory was of consistent quality. Finally on the basis of test results, the HPC with silica fumecontent 7.5 and 10 %, Indian cement and aggregate is recommended for the use in containment structure. The final fieldapplication is, however, subjected to 'Information and qualification test' which is in progress.