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In this study, it is investigated the properties of high strength concrete using mineral admixture, on the purpose of use of meta kaolin for the substitutive materials to silica fume which is so expensive. The plain mixtures are 3 degrees which are ordinary portland cement, blast furnace slag cement and OPC included fly ash 20%, and silica fume and meta kaolin are substituted for the each plain mixtures in the range of 20%. The results of experiment showed as follows. In case of silica fume was only used, the viscosity and slump flow of fresh concrete were much decreased, on the contrary air content increased. But as usage of meta kaolin increased, to being increase the viscosity of fresh concrete, slump flow increased and air content and usage of super-plasticizer were decreased. Accordingly the workabilities of concrete were against tendency between silica fume and meta kaolin. The compressive strength, velocity of ultrasonic pulse and unit weight were increased according to usage of meta kaolin, the properties of hardened concrete were judged that they are affected with air content of fresh concrete, so it is very important to control air content of high strength concrete. Therefore, the use of meta kaolin is prospected to the substitutive material of silica fume, in case of using silica fume and meta kaolin, it is judged that the optimum usage of silica fume and meta kaolin is about 10% respectively, considering workability and strength of concrete.

There is currently a need to evaluate the non-destructive techniques that are used to detect the fracture of stressed steel wires in grouted post-tensioned concrete bridges. Although continuous acoustic emission (AE) monitoring technique has been developed to detect wire breaks in unbonded tendons, it is not established as the on-site monitoring tools for grouted post-tensioned concrete bridges. In this study, AE measurements were conducted to detect corrosion-induced wire fractures inside a grouted post-tensioned beam. The test beam was drilled with 5mm drill bit to expose individual wires and a reservoir filled with corrosive solution of NaCl and NaOH was formed on the side of the beam. During the experiment, the corrosion site was anodically polarized to + 200mV using a potentiostat and it was continuously monitored and the data obtained were processed with an AE monitoring system. The outcome of this research shows that the continuous AE monitoring system successfully identified and located an individual corrosion-induced wire fracture in a fully grouted post-tensioned concrete beam.

This paper presents experimental test results on corrosion resistance of concrete containing ground granulate blast-furnace slag (GGBS) and ASTM Type I or ASTM Type V cement. To investigate the problem, a series of tests were performed. First, rapid chloride permeability tests were executed in accordance with ASTM C 1202 to determine the qualitative terms of chloride-ion penetrability. Second, accelerated chloride-ion diffusion tests were done to calculate diffusion coefficients of chloride-ions permeated through concrete specimens. Third, accelerated steel corrosion tests were carried out by using the repeated wetting and drying technique. Fourth, half-cell potential tests were implemented in accordance with ASTM C 876 to evaluate the probability of steel corrosion. Finally, the surface area of corrosion on embedded steel in concrete specimens was measured to confirm half-cell test results. Test results showed that the coefficient of permeability of Type I cement concrete was lower than that of Type V cement concrete. All the concrete mixed with GGBS exhibited lower diffusion coefficient, compared to GGBS-free concrete. Moreover, the corrosion probability of steel bar in Type V cement concrete was higher than that of steel bar in Type I cement concrete. Based on the test results, it is suggested that much stronger corrosion resistance can be achieved, if higher volume of GGBS is added in Type I cement rather than Type V cement.

In this study, a mix design for self compacting concrete was based on Okamura's method and concrete incorporated just a ground granulated blast furnace slag. Replacement ratio of slag is in the range of of cement matrix by volume. For the optimal self compactability in mixture incorporating ground granulated blast furnace slag, the paste and mortar tests were first completed. Then the slump flow, elapsed time of 500mm slump flow, V funnel time and filling height by U type box were conducted in concrete. The volume of coarse aggregate in self compacting concrete was in the range of to the solid volume percentage of coarse aggregate. Finally, the compressive and splitting tensile strengths were determined in the hardened self compacting concrete incorporating ground granulated blast furnace slag. From the test results, it is desirable for self compacting concrete that the replacement of ground granulated blast furnace slag is in the range of of cement matrix by volume and the volume of coarse aggregate to the solid volume percentage of coarse aggregate with a limit of .

The behavior of chloride ions introduced into concrete from concrete surface by marine environment and by use of marine aggregate was analyzed for a coastal concrete structure. A mathematical model including the diffusion of chloride ion in aqueous phase of pores, the adsorption and desorption of chloride ions to and from the surface of solid phase of concrete, and the chemical reactions of chloride ions with solid phase was presented. Finite element method was employed to carry out numerical analysis. Quantitative analysis was conducted to measure the distribution of the free chloride ion concentration in aqueous phase of concrete with potentiometric titration based on ASTM D 1820. The concentration profiles of chloride ions predicted by the mathematical model agreed favorably with the measured data. The results of this study may be used to predict the onset of reinforcement corrosion and to identify the maximum limit of chloride ions contained in concrete admixtures.