• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.04a
• /
• pp.101-102
• /
• 2022

A new hydrazone derivatives namely (E)-N'-(4-(dimethylamino)benzylidene)-2-(5-methoxy-2-methyl-1H-indol-3-yl)acetohydrazide (HIND) has been confirmed for mitigating the corrosion of the steel rebar exposed to chloride contaminated synthetic concrete pore solution (ClSCPS). The mitigation of corrosion properties has been characterized by weight loss and electrochemical methods (Electrochemical impedance, Potentiodynamic polarization studies) as well as surface observations. The presence of HIND in the ClSCPS decreased the corrosion of steel rebar by adsorption of HIND molecules on the surface of the steel rebar. The optimal HIND concentration was 0.5 mmol/L, corresponding to an inhibition efficiency of 88.4%. The use of HIND enables the corrosion process to have a higher energy barrier. X-ray photo electron spectroscopy (XPS), atomic force microscopy (AFM), scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), and X-ray diffraction (XRD) spectroscopy interpretations confirmed that HIND mitigates the corrosion attack on the surface steel rebar.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.12
• /
• pp.25-32
• /
• 2007

This study is to evaluate the effect of chemical attack on durability and deterioration of lining concrete in tunnel. Surface examination, nondestructive inspection, uniaxial compressive strength test, carbonation test, chloride diffusion test, micro-structural analysis were performed to analyze the deterioration of lining concrete in tunnel constructed 70 years ago. From surface examination results, the tunnel had been repaired and reinforced in several times. It has many cracks, water-leakage, efflorescence and exploitation. Compressive strengths obtained from nondestructive inspection and uniaxial compressive strength test have measured $17.5{\sim}34.7MPa$, and $12.8{\sim}40.3MPa$, respectively. Carbonation depth specimen cored from concrete lining has ranged from 3mm to 27mm. From chloride diffusion test, most specimens have low permeability. And the XRD analysis was able to detect ettringite and thaumasite, which were confirmed by SEM and EDS results to be the causes for the deterioration of lining concrete.

• Journal of the Korean GEO-environmental Society
• /
• v.19 no.12
• /
• pp.59-64
• /
• 2018

The damages to the reinforced earth retaining wall are divided into the front wall, foundation, drainage and upper slope. Damage of reinforced earth retaining wall is mainly caused by damage caused by drainage problem in the field. Recently, damage caused by snow removal materials have been occurred. Recently, the amount of snow removal materials used in winter is increasing due to abnormal weather. This chlorides degrades the concrete structure, where the reinforced earth retaining wall was no exception. There has recently been a case in which the front wall of the reinforced earth retaining wall deteriorates due to the chlorides introduced into the back filling portion through the drainage passage. Therefore, in this study, the cause of damages of reinforced earth retaining wall constructed in bridge abutment was analyzed, and an analytical study was conducted on the countermeasure. As a result, it was found that chlorides, which was introduced through the drainage system in the expansion joint of the bridge shift part or the upper structure, is infiltrated into the back part of the reinforced earth retaining wall and damaged. Therefore, it is suggested to improve the drainage system and restored the stiffness of the front wall.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.2
• /
• pp.10-19
• /
• 2019

Management plan with repairing is essential for RC structures exposed to chloride attack since durability problems occur with extended service life. Conventionally deterministic method is adopted for evaluation of service life and repair cost, however more reasonable repair cost can be obtained through continuous repair cost from probabilistic maintenance technique. Unlike the previous researches considering only normal distribution of life time, PLTFs (Probabilistic Life Time Function) which can be capable of handling log and normal distributions are attempted for initial and repair service life, and repair cost is evaluated for OPC and GGBFS concrete. PLTF with log distributions in initial service life is more effective to save repair cost since it is more dominant after average than normal distribution. Repair cost in GGBFS concrete decreases to 30% of OPC concrete due to longer initial service life and lower repairing event. The proposed PLTF from the work can handle not only normal distributions but also log distributions for initial and repair service life, so that it can provide more reasonable repair cost evaluation.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.1
• /
• pp.89-96
• /
• 2023

In this paper, a ferrosilicon by-product was evaluated to confirm the feasibility of recycling it as supplementary cementitious material of ordinary Portland cement in concrete. Three different levels of replacement ratio (10 %, 20 % and 30 % of total binder) were applied to find which is the most beneficial to be used as a binder. Ferrosilicon concrete was initially assessed at setting time and compressive strength. Durability was evaluated by the resistance to chloride penetration test(RCPT) and alkali-silica reaction(ASR) with a comparison to silica fume concrete due to their similarity in chemical composition. The porosimetry and X-ray diffraction analysis along with energy dispersive X-ray spectroscopy give information on the microstructural characteristics of the ferrosilicon concrete. It was found that 10 % ferrosilicon concrete has higher strength while 20 %, 30 % have lower strength than OPC concrete. However, chemical resistance to chloride attack is higher when replacement is increased. Compared to silica fume, the durability of ferrosilicon might be less efficient however, it is obviously beneficial than OPC. High SiO₂ content in ferrosilicon results in producing more C-S-H gel which could make denser pore structure. Most of the risk of alkali silica reaction to silicate binders through length change tests was less than 0.2 %, and both mortar using ferrosilicon and silica fume showed better resistance to alkali silica reaction as the substitution rate increased.Reuse of industrial waste rather than producing highly refined additives might reduce environmental load during manufacture and save costs.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.4
• /
• pp.1-9
• /
• 2020

This study conducted to understand effects of CA (CaAl₂O₄) and CA₂ (CaAl₄O₇) ratio on chloride binding ability and compressive strength and pore structure of cement mortar incorporating mixture of CA and CA₂. The Portland cement based specimens were mixed with the clinkers CA and CA₂, and these calcium aluminate clinker mixture were replaced 0, 5, 10% by weight of cement. After all the test specimens were cured for 28 days under water curing, they were immersed in the distilled water and NaCl solution. As a result, 28 days compressive strength of all specimens was similar, and As the replacement ratio of calcium aluminate clinker in the specimen increased, Friedel's salt production tended to increase. However, it was dependent on the amount of Al₂O₃ in the level of 5% replacement and CA ratio in the level of 10% replacement. Through equilibrium isotherm result, it was also indicated that as replacement ratio of calcium aluminate clinker in cement matrix increased, chloride binding capacity was improved, and chloride penetration was suppressed. In this study, the specimen replaced with 10% of the calcium aluminate clinker mixture (CA 39%, CA₂ 60%) was remarkable to control chloride attack. We figured out necessity to understand optimal CA/CA₂ ratio to effectively apply CA₂ as a sustainable building material by improving the chloride binding ability in Portland cement based system.

• Journal of the Korea Institute of Building Construction
• /
• v.5 no.3 s.17
• /
• pp.75-82
• /
• 2005

Sewage facilities are positively necessary for environment improvement such as rainwater removal, sewage disposal, preservation of the quality of water and health of the citizens in present-day. Meanwhile, a deterioration of the concrete sewer pipe is increasing rapidly due to the chemical and physical attack and especially biochemical attack that is to say biodeterioration. So, in advanced countries, prediction techniques and corrosion inhibition system for sewer concrete are developed and are being applied. Also, antibiotics were developed already but application of that is low because it is not economical and has no practical use. But, in domestic, countermeasures for the corrosion of sewage concrete are not sufficient and biochemical attack is not reflected in those essentially. In this study, to prevent biochemical corrosion of the sewer concrete, surface of the concrete was spread with liquefied inorganic antibiotics and then its engineering properties were experimentally investigated. As a result, compressive strength of the specimen spread with antibiotics were similar to those of non spread, Both bond strength and abrasion amount of the specimen spread with antibiotics were inferior to non spread. Properties of absorption and air permeability of the specimen spread with antibiotics were superior to non spread. Finally, carbonation depth, chloride ion penetration depth and weight change ration of the specimen spread with antibiotics were smaller than non spread.

• Journal of the Korea Concrete Institute
• /
• v.22 no.6
• /
• pp.769-776
• /
• 2010

Concrete structures immersed in seawater are exposed to uniform chloride concentration. However, seashore concrete structures are subjected to various airborne chlorides concentration depending on areas, distance from seashore, orientation of structures and wind direction etc. Therefore, structures which is not coming into direct contact with seawater are greatly affected by salt attack and those cases have been reported. This study intends to investigate salt attack by airborne chlorides in terms of the distance from the seashore based on the measurements conducted at 73 spots and 27 areas during 3 years in the Eastern, Western and Southern coasts of South Korea. Results revealed large regional variations of the salinity in coastal regions along with significant seasonal effects caused by seasonal winds. Moreover, the salinity is seen to diminish as the distance from the seashore increases at a rate corresponding to the function $y=ax^{-b}$. These results will be helpful to do the durability design and management of seashore structures.

• Journal of the Korea Concrete Institute
• /
• v.21 no.3
• /
• pp.359-366
• /
• 2009

A new life-cycle cost (LCC) evaluation scheme for marine reinforced concrete structures is proposed. In this method, unlike the conventional life-cycle cost evaluation performed during the design process, the life-cycle cost is updated successively whenever new information of the chloride penetration is available. This updating is performed based on the Bayesian approach. For important structures, information required for this new method can be obtained without any difficulties because it is a common element of various types of monitoring systems. Using the new method, the life-cycle maintenance cost of structures can be estimated with a good precision.

• Journal of Environmental Science International
• /
• v.17 no.5
• /
• pp.509-516
• /
• 2008

New functional surfactant, N,N-dimethyl-N-dodecyl-N-(2-methyl benzimidazoyl) ammonium chloride(DDBAC) having benzimidazole(BI) functional group have been synthesized and the critical micellar concentration of DDBAC measured by surface tentiometry and electric conductivity method was $8.9{\times}10^{-4}M$. Micellar effects in DDBAC functional surfactant solution on the hydrolysis of p-nitrophenylacetate(p-NPA), p-nitro-phenylpropionate(p-NPP) and p-nitrophenylvalerate(p-NPV) were observed with change of various pH (Tris-buffer). The pseudo first rate constants of hydrolysis of p-NPA, p-NPP and p-NPV in optimum concentration of DDBAC solution increase to about 160, 280 and 600 times, respectively, as compared with those of aqueous solution at pH 8.00(Tris-buffer). It is considered that benzimidazole functional moiety accelerates the reaction rates of hydrolysis because they act as nucleophile or general base. In optimum concentration of DDBAC solution, the rate constants of hydrolysis of p-NPP and p-NPV increase to about 1.5 and 3.0 times, respectively, as compared with that of p-NPA. It means that the more the carbon numbers of alkyl group of substrates, the larger the binding constants between DDBAC micelle and substrates are. To know the hydrolysis mechanism of p-NPCE(p-NPA, p-NPP and p-NPV), the deuterium kinetic isotope effects were measured in $D_2O$ solutions. Consequently the pseudo first order rate constant ratios in $H_2O$ and $D_2O$ solution, $k_{H_2O}/k_{D_2O}$, were about $2.8{\sim}3.0$ range. It means that the mechanism of hydrolysis were proceeded by nucleophile and general base attack in approximately same value.