Study On Methods Of Accelerated Testing Of Marine Concrete Durability Based On Simulating Environment And Service Life Prediction

The durability accelerated testing methods based on single-factor action are invalid in service life prediction and durability design of marine concrete in engineering because of absence of multi- factor action of similar actual environment.Airming at these problems of research on durability testing methods and method of service life prediction,some innovative study work are explored in this paper.The main contents and achievements are as follows:1)The transfer mechanisms of harmful substance in concrete and relationship between transfer mechanism and deterioration mechanism of marine concrete in various environmental conditions are discussed.Foundation on service life prediction based on zone environment is established.2)The two basic issues of study on marine concrete durability and service life prediction,which are pore solution making method of concrete and depassivation critical value of steel bar embedded in concrete are investigated.A simple and practical artificial pore solution making method of concrete is presented,and relationship between the parameter such as [OH-] of this artificial pore solution and that of expression pore solution is established.Analyse on the depassivation critical value of steel bar embedded in concrete indicate that the depassivation critical value of steel bar is not only dominated by the parameter of [Cl-],but by the parameter of [OH-] or alkalinity of concrete,and a series of theoretic analyse and experimental data also indicate that half-cell potential of steel bar embedded in concrete is the bivar linear function of log[Cl-] and pH value of pore solution of concrete.3)Based on analysis and summarization of rapid testing methods for chloride diffusion coefficient of concrete, two issues concerned in this field have been put forwarded. Aiming at solving the problems, basic theory, application condition, as well as amendatory methods on rapid testing chloride diffusion coefficient of concrete based on electrochemistry method have been discussed, and a new method for chloride diffusion coefficient of marine concrete saturated with seawater ground on electrical resistivity measurement has been suggested. Experimental results show that this new method is not only correct in theory but dependable in practice. At the same time the experimental results also indicated that the chloride diffusion coefficient can be decresed greatly by adding 25% FA and 25% SG replacing 50% cement in concrete.Service life prediction on normal concrete and concrete with high conctent FA and SG of various W/B is completed by using Monte Carlo stochastic simulation method.4) On the basis of study of gas transfers mechanism into porous medium materials, a calculation formula of gas effective diffusion coefficient of concrete based on pressure grads and water saturation has been deduced according to the relevant theory. According to the testing method and calculation formula,the gas effective diffusion coefficient of HPC and old concrete with higher pressure grads has been tested and calculated. Making use of the relationship model between the gas effective diffusion coefficient of concrete and the gas diffusion coefficient in straight capillary pore, the pore tortuosity factor in concrete has been caculated. The experimental results is basically coincide with that of Switzerland scholar Houst F I and Wittmann Y F using concentration grads method. The analysis of pore structure indicates that the total pore ratio of concrete calculating from cement paste pore ratio by using MIP thchnique can bring prodigious...