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Jeong, Jin-A,Jin, Chung-Kuk,Kim, Yong-Hwan,Chung, Won-Sub Japan Concrete Institute 2013 Journal of advanced concrete technology Vol.11 No.1
<P> In recent years, an interes in the corrosion monitoring technique of steel in marine concrete structures has been increased. Monitoring the reinforcement corrosion, it is crucial to be aware of corrosion threshold for damages or early repair and rehabilitation due to economical and safety aspects. A number of corrosion monitoring sensors have been proposed world-widely to predict the proper repair time of concrete structures. However, most of sensors introduced so far have some limitations to reach to the reliable status to evaluate corrosion continuously and accurately. A multi-functional compact sensor to monitor several corrosion factors has been proposed in this study, and the electrochemical and physical evaluation has been carried out to investigate rebar potential, corrosion rate, passivation state of rebar surface, and temperature of concrete. Five different environments, i.e. atmospheric, tap water, seawater, 15% seawater, and 15% seawater wet-dry cycle, have been applied, and a reasonable prediction of corrosion has been obtained in terms of non-destructive electrochemical point of view. </P>
Experimental Study on Blast Resistance of SIFCON
Chun, Pang-jo,Lee, Sang Ho,Cho, Sang Ho,Lim, Yun Mook Japan Concrete Institute 2013 Journal of advanced concrete technology Vol.11 No.4
<P> Slurry infiltrated fiber concrete (SIFCON) have received considerable attention in recent years. The SIFCON is distinguished from the conventional steel fiber reinforced cementitious composite (FRCC) by its high volume ratio of fibers, far beyond that of typical steel FRCC. Although this material has already been used for important structures including power plants and military facilities, very little is known about its behavior under blast loading. We therefore have experimentally investigated the behavior of SIFCON under the contact blast loading for the first time. This paper is intended to report these blast test results, in which varying amounts of gelignite embedded in the specimens were set off. After the blast test, diameter of crater, diameter of inlet of charge hole, and bulge of top surface of SIFCON were measured from the pictures using a commercial stereophotogrammetry program ShapeMetrix3D, and compared them to that of the conventional high strength concrete. The comparison results show the much higher blast resistance of SIFCON over conventional high strength concrete. In addition, the coefficient of resistance of SIFCON is evaluated which helps us to design the SIFCON structure subject to blast loading </P>
Tension Stiffening Model for Numerical Analysis of RC Structures by Using Bond-Slip Relationship
Japan Concrete Institute 2009 Journal of advanced concrete technology Vol.7 No.1
<P>In this paper, a tension stiffening model based on the bond-slip relationship is introduced and adopted in a finite multilayered shell element formulation for surface structure analysis. The tension stiffening effect evaluated at the meso-level is taken into account in the constitutive law of reinforcement at the macro level by defining a crack element at the Gauss point. The crack element is iteratively analyzed by means of a step-by-step integration, which allows application of any complicated bond laws. To define the crack element, a crack spacing model considers the crack formation grade. As a relevant factor in this tension stiffening concept, the reinforcement cracking stress may be evaluated by taking the fractile value of the concrete tensile strength. Through several simulations, the validity of the concept is systematically in-vestigated under monotonic and cyclic loading. The analysis under cyclic loading shows the effect of the re-contact of the crack flanks. The numerical examples demonstrate the applicability of the applied reinforced concrete model with a tension stiffening effect.</P>
Fundamental Property of Chloride Inhibiting and Low Heat Cement for Marine Concrete Structures
Park, Cheolwoo,Sim, Jongsung,Lee, Jongryul Japan Concrete Institute 2009 Journal of advanced concrete technology Vol.7 No.1
<P>As the construction of marine concrete structures become more common, durability issues are gaining importance. This study introduces a newly developed chloride-inhibiting low-heat cement that is a quaternary blended cement. The primary target application of the newly developed cement is massive marine concrete structures. The adiabatic temperature rise of the newly developed cement was about 30% and 28% lower than for ordinary Portland cement and blast furnace slag cement, respectively, and resistance to chloride ion penetration was much higher compared to blast furnace slag cement. Based on the ASTM C1202 guidelines, the adiabatic temperature rise of the new cement could be considered very low at 28 days, while that of the blast furnace slag cement was in low range. Thus the primary purposes of the newly developed cement can be said to have been successfully attained. In addition, the developed chloride-inhibiting and low-heat cement may satisfy the strength requirement of general-purpose marine concrete applications without significant concerns regarding early-age strength. The developed cement was shown to provide sufficient resistance to freezing-thawing attack as long as proper air content is obtained.</P>
Tidal Water Effect on the Hybrid Cathodic Protection Systems for Marine Concrete Structures
Jeong, Jin-A,Jin, Chung-Kuk,Chung, Won-Sub Japan Concrete Institute 2012 Journal of advanced concrete technology Vol.10 No.12
<P> This paper represents the behaviors of hybrid cathodic protection (hybrid CP) system in a reinforced concrete column specimen. Cathodic protection (CP) is widely used as a means of protecting corrosion for marine concrete structures such as harbor and offshore facilities. Specifically, hybrid CP, which is the combination both sacrificial anode cathodic protection (SACP) system and impressed current cathodic protection (ICCP) system, can be an optimum way to protect corrosion. Some complex concrete structures as well as harbor constructions are considered to be protected by both systems. Especially, it becomes more complicated to protect corrosion damage of concrete structures in the tidal and splash zones of marine environment. In case of Yellow Sea of the South Korea, the tidal zone reaches to 6~8m. On the condition that this system is well applied in the Yellow Sea, it is expected to show a good CP behavior to solve an underprotection problem, especially in tidal and splash zones. In this study, the hybrid system installed both the ICCP with Timesh anode and the SACP with zinc anode has been adopted to verify the current influence through laboratory experiment. CP potential and current have been investigated, in addition, 4-hour depolarization test has been involved to reveal the effectiveness of hybrid CP. </P>