Life Cycle Theory-Based Durability Optimized Design Of Marine Concrete

Based on concrete structure life cycle theory, the marine concrete durability deterioration under the chloride attack is studied, with the discussion on concrete design and performance optimization and the life span analyzing that considers economic and social benefit. The principle of material choosing and application is proposed. A chloride investigation database is established by onsite detecting, exposure tests, artificial simulating tests and accelerated tests in and abroad. The chloride resistance paten of the detected marine concrete is discussed. Under the requests of concrete durability and CO2 emission limitation, a modified concrete design method which is in concern with the chloride resistance and energy saving of the marine concrete is suggested. Concrete mixture design software is developed.The flow of this research is as follows.1. The fractal theory is introduced into the analysis of fine aggregates particles distribution. The mass and volume fractal dimensions of aggregates piles are deduced. Experiment is designed to detect the relationship between fine aggregates grading and concrete performance. Numerical study is adopted too. A two-dimension circle aggregate distribution model is set up. The aggregates volume fraction is transformed into circle aggregate area volume in the finite element computerization. The experiment results metchs with the numerical computering results.2. A chloride investigating database is established. It contains different data from:â‘ etecting the chloride resistance of the marine concrete structures on the specific ports in Zhejiang province and Japan;â‘¡xposure testing in Hangzhou Bay Bridge and Port and Airport Research Institute, Japan;â‘¢accelerated tests of artificial environments simulating tests and the electrical accelerated tests. The database also collects the material, climate and environmental information. Web technology combined with Django software is introduced to setup a database managing system. MySQL is planted in the system to manipulate the database system. This database is an important information source for the life cycle theory-based concrete durability research and to support the evaluation of the marine concrete structures chloride resistance.3. The co-effect of initial curing condition and exposure environments on concrete chloride resistance is discussed by experiment. Two methods of exposure testing and steady state migration tests are adopted. The chloride transportation model in unsaturated concrete is used to simulate the chloride movement characters in longer term's exposure. The curing effect coefficient kc on chloride resistance of concrete is suggested for different service environments. The different initial curing conditions are advised for the concrete to use in different environments too.4. Based on the established database, the time dependent reducing parameters of the chloride diffusion coefficients Da and the migration coefficients DRCM are worked out. The empirical expressions of these two parameters are given. By considering the suggestion in<Guide to durability design and construction of concrete structures>, the migration coefficient DRCM,28 at 28d age is determined as the durability design index of concrete material. By introducing the multi-environmental time similarity (METS), the relationship between Da and DRCM is studied. The material effect coefficient Kmateriai and environment effect coefficient ke are also studied. Their values in specific conditions are suggested.5. The relationship between concrete mixture design indexes and the chloride resistance is developed by using nonlinear analysis methods. The nonlinear and neural network predicting models are established to estimate the DRCM,28 values from the concrete mixtures. The predicting models are introduced into the traditional concrete mixture design process. In addition, the CO2 emission of marine concrete material manufacturing, transportation and construction are considered. A piece of designing software is developed. The benefits of the optimized concrete on economy, energy saving and service life expending are obtained.This research was supported by the project of National Natural Science Fund "Fundamental Research on Durability Design and Assessment of Concrete Structures in Chloride Erosive Environment" (50538070), the science and technology project of Zhejiang Province "Key Anti-corrosion Techniques of Harbor and Costal Engineering and Development and Application of Supporting Facilities" (2006C13090), the agreement project of Chinese and Japanese (NSFC/JSPS) "Durability design theory of concrete structure based on Life-Cycle Cost Management Technique", the science and technology project of Zhejiang Province "Durability Research and Monitory Technique on Jiubao Project-Durability Study on the Composite Structural Bridge". Their support is gratefully acknowledged.