Jae-Cheol Ahn

Development of Multidirection Incoming Salt Collector that Excludes Backward Wind

Evaluation of the amount of chloride ion coming from the sea is very important in assessing the life expectancy of Reinforced Concrete structures. Developed in Japan, the incoming salt collector has been used to this day. Unfortunately, the incoming salt collector has had a bad reputation, which is caused by backward wind. Backward wind causes a reduction of the amount of salt collected in collector`s gauze. The collector was developed to eliminate the effect of backward wind. Simulation test in the laboratory and site measurement were performed to determine the amount of incoming salt according to the height. The performance was verified through analytic and experimental methods.

Disassembly Properties of Cementitious Finish Joints Using an Induction Heating Method

Efficient maintenance and upgrading of a building during its lifecycle are difficult because a cementitious finish uses materials and parts with low disassembly properties. Additionally, the reuse and recycling processes during building demolition also present numerous problems from the perspective of environmental technology. In this study, an induction heating (IH) method was used to disassemble cementitious finish joints, which are widely used to join building members and materials. The IH rapidly and selectively heated and weakened these joints. The temperature elevation characteristics of the cementitious joint materials were measured as a function of several resistor types, including wire meshes and punching metals, which are usually used for cementitious finishing. The disassembly properties were evaluated through various tests using conductive resistors in cementitious joints such as mortar. When steel fiber, punching metal, and wire mesh were used as conductive resistors, the cementitious modifiers could be weakened within 30 s. Cementitious joints with conductive resistors also showed complete disassembly with little residual bond strength.

Study on CO 2 Emission Reduction Effects of Using Waste Cementitious Powder as an Alternative Raw Material

With environmental regulations continuously being strengthened internationally the need to control environmental pollution and environmental load is emerging in Korea. The purpose of this study is to seek methods or using waste cementitious powder as an alternative raw material for limestone through the optimization of raw material and to quantitatively analyze the resulting reduction of CO₂ emission in order to contribute to solving the issue of waste, which is the biggest issue in relation to construction and global warming. The results of the study, show that waste cementitious powder can be used as an alternative raw material for limestone at OPC level, but it was also found that mixing fine aggregate cementitious powder into waste cementitious powder significantly affected the substitution rate for limestone with waste cementitious powder and the reduction of greenhouse gas. In particular, when fine aggregate cementitious powder was used at a rate of 0~20%, the substitution rate for limestone and the reduction in the rate of greenhouse gas emission was significantly reduced. It is thought that a technique to efficiently separate and discharge the fine aggregate cementitious powder mixed in waste cementitious powder needs to be developed in the future.

The Property Evaluation of the Marine Concrete Structure Constructed in the Period of Japanese Occupancy (YoungDo Bridge)

YoungDo bridge is the first suspension bridge in Busan which experienced several times repair and reinforcement after completion in 1934. The bridge is under demolition for extension and restoration work since 2011. The purpose of this research is to establish data base about modern concrete. The mix design of the concrete is like that cement : fine aggregate : coarse aggregate

Development of Testing and Analysis Model for Evaluation of Absorbed Water Diffusion into Concrete

Concrete is affected by various deterioration factors, such as and chloride ions from the sea, which cause carbonation and salt attack on concrete. These deterioration phenomena cause steel corrosion in RC structures. Although a great deal of research has been carried out in this area thus far, it is difficult to know the point at which corrosion will occur to a reinforced bar. As the diffusion of deterioration factors depends on the water content in concrete, it is imperative to assess the condition of absorbed water content. A mass measuring method was applied to calculate the absorbed water diffusion coefficient, as well as non-linear finite element method(FEM) analysis. As a result, it was found that W/C and unit water content in concrete mixture affect the diffusion coefficient decision.