| Self-compacting concrete (SCC) is widely accepted by engineers and researchers due to its excellent workability and environmental friendly properties. In this research, the properties of SCC which was utilized in nuclear power plant, such as mix design, mechanical properties, durability and shrinkage crack resistance, were investigated in comparison with normal vibrating concrete (NVC). Focusing on the concrete structure durability in complicated environment, the time dependence properties simulation and analysis of concrete were discussed in multi-factor coupling conditions. The subjects of this research include:(1) In considering the operation convenience, a simplified method on estimating the specific surface of aggregate was put forward based on improved Heywood single aggregate surface calculation equation. The coarse-to-fine degree and particle size distribution of aggregate were taken into account in this method and two new concepts, surplus thickness of sand and thickness of paste around aggregate, were introduced. Then take the two new concepts as the breakthrough point, this research proposed a new mix design method of SCC. Two kinds of SCC, C35 and C50, were designed with this method and tested through both indoor and outdoor experiments. The test results indicated that the SCC designed with new method showed good behaviors in mechanical properties and workability.(2) The cubic compressive strength, cubic splitting tensile strength, axial compressive strength, elastic modulus, flexural tensile strength, steel bonding strength and flexural cracking strain of both SCC and NVC in C35 and C50 were investigated from 3d to 560d. The research revealed the long term development of mechanical properties with time and the inter-relationship between them of SCC against NVC. A further comparison of the durability and shrinkage cracking resistance between SCC and NVC was conducted in terms of permeability resistance test, chloride penetration resistance test and carbonation resistance test, as well as the free shrinkage test, plate cracking restraint test and ring cracking restraint test. The test results showed that mechanical properties, durability and shrinkage cracking resistance of SCC all beat NVC.(3) Based on Fick diffusion law and mass conservation law, a theoretical model of concrete moisture field was established. The high similarity between moisture field and temperature field of concrete was applied to digitally solve the moisture field problems with converted temperature field. In view of dry-shrinkage and wet-expansion effect of moisture field, this research put forward a new method to identify the moisture field parameters by concrete shrinkage curve under different drying conditions. The calculation on 4 kinds of concretes verified the accuracy and convenience of the new method.(4) Based on the assumption of anisotropic strain damage and introduction of damage factor in concrete element, a new concept of anisotropic diffusion enhancing factor was defined and applied to modify moisture, carbon dioxide and chloride diffusion coefficients on damage and cracking of concrete element. The diffusion enhancing factors of moisture, carbon dioxide and chloride can all be easily implemented in finite element analysis and improve the accuracy of simulation calculation.(5) Based on literatures review, Fick diffusion law and mass conservation law were applied in theoretically modeling the carbon dioxide field and chloride field under multi-factor coupling conditions, such as temperature, moisture and stress. Carbon dioxide field and chloride field were both translated to temperature field for simulation analysis according to the high similarity between carbon dioxide field, chloride field and temperature field. Simulation analysis of carbon dioxide field and chloride field was verified by accelerated carbonation experiment and chloride penetration experiment with pre-cracked concrete specimen. Both the simulation results of carbon dioxide field and chloride field showed good agreement with experiments results. Aiming at the application on the generally used finite element program platform, basic process framework of time dependence simulation analysis of concrete under multi-factor coupling conditions was built.The research can provide a simple and practical mix design method and reliable test data base for a wider application of SCC in nuclear power constructions and other engineering projects. At the same time, this investigation will offer some useful references for durability analysis and service-life-span prediction of concrete structure in complicated environments.The research was financially supported by National Science Foundation (Grant No. 50838008), National Basic Research Program of China (973 Program, Grant No. 2009CB623200), Doctoral Program of Higher Education (No. 20070335087) and High Technology Research and Development Program of China (863 Program, 2006AA04Z415).
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