Papers by Author: In Seok Yoon

Abstract: The purpose of this study is to identify and quantify the effect of the mixing features of concrete such as size of coarse aggregate, high strength and steel fiber reinforcement on chloride penetration through micro-cracks. In examining the effect of size of coarse aggregate on chloride penetration through cracks, the cracks should not impact on chloride penetration directly, although small size of coarse aggregate can lead to complicated micro-cracks in concrete. On the contrary, chloride should easily penetrate through micro-cracks concentrated at the surface of coarse aggregates. In examining the effect of high strength concrete on chloride penetration through cracks, high strength concrete has an excellent performance to resist with chloride penetration. If cracks are generated in high strength concrete, however, its performance is reduced up to the level of ordinary concrete.

Abstract: The most common deterioration cause of concrete structures over the world is chloride ions attacks. Thus, service life modeling of concrete is a crucial issue in civil engineering society. Many studies on the topic have been accomplished, however, it is not easy to review literatures about environmental analysis, in particular micro-climatic condition of concrete under chloride laden environment. Since the durability of concrete depends on the properties of the surface concrete, micro-climatic condition which influences on surface concrete realistically should be considered. This study is devoted to analysis the micro-climatic condition of concrete structures, based on the in-situ monitoring of weather in marine environment. The outcome will be combined with modules of material parameters such as chloride diffusivity, surface chloride content, and so on. It is expected that the result of this work should be available for the prediction of chloride profile of marine concrete at atmospheric zone or tidal zone.

Abstract: This study is focused on examining the effect of cracks on chloride penetration into concrete. In order to get reliable results, short-term and long term experiments were set up and chloride penetration behaviour through cracks was examined. It was noticed that chloride penetration through cracks tends to decrease with time. One of the explanations is crack-healing. Especially, this trend was obvious in concrete samples with larger crack width. However, measuring the border between chloride contaminated zone and healthy zone was clear in concrete of short-term experiment, while it was ambiguous in long term experiment.

Abstract: The surface treatment system is one of the best options to extend the service life of marine concrete in terms of cost effectiveness versus durability performance. In order to establish rational maintenance strategies for surface treated concrete structures, however, it is necessary to define how to quantify and how to optimize the performance of the surface treatment system. The solution could be obtained from the prediction of chloride in surface treated concrete. In this study, theoretical solution to predict the behavior of chloride diffusion in surface treated concrete is constructed.

Abstract: The purpose of this study is to establish a simple approach to compute the chloride diffusivity of (non)carbonated concrete. The chloride diffusivity of concrete should is defined, based on engineering and scientific knowledge of cement and concrete materials. In this paper, parameters affecting the chloride diffusivity, such as the diffusivity in pore solution, tortuosity, micro-structural properties of hardened cement paste, volumetric portion of aggregate, are taken into consideration in the calculation of the chloride diffusivity of noncarbonated concrete. For carbonated concrete, reduced porosity due to carbonation is calculated and used for calculating the chloride diffusivity. The results are compared with experimental data and previous research works.

Abstract: The ingress of chloride ions plays a crucial role for service life design of reinforced concrete structures. In view of durability design of concrete structures under marine environment, one of the most essential parameters is the surface chloride content of concrete. With the social and technical backgrounds, the research approach of this study starts with the calculation of the amount of chloride ingredients in normal sea water. The capillary pore structure is modeled by numerical simulation model HYMOSTRUC and it is assumed to be completely saturated by the salt ingredients of seawater. In order to validate this approach, the total chloride content of the mortar and concrete slim disc specimen was measured after the immersion into the artificial sea water solution. Additionally, the theoretical, the experimental and in-situ investigation results of other researchers are compiled and analyzed. Based on this approach, it will follow to calculate the maximum surface chloride content of concrete in the tidal zone, where the environment can be considered as subjected to dry-wetting cycles.