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Concrete with blast furnace slag (BFS) shows varied strength development properties under general temperature conditions. Therefore, a precise prediction of compressive strength using a full maturity model is desired. The purpose of this study is to predict the compressive strength of concrete with BFS by calculating the apparent activation energy (Ea) for each BFS replacement ratio, applying this activation energy to the equivalent age model, and then using the Carino model. For BFS replacement ratios of 0%, 10%, 30%, and 50%, Eais calculated as 33.475 kJ/mol, 37.325 kJ/mol, 41.958 kJ/mol and 45.541 kJ/mol respectively. Finally, the compressive strength of concrete with BFS is predicted.

The durability of a concrete structure is most significantly influenced by the corrosion of reinforcing bars, rather than by the deterioration of concrete itself. The corrosion of reinforcement bars due to chloride serves as a main deterioration factor at the interface between the bars and the concrete in the concrete structure. Accordingly, the corrosion inhibitors are widely used to improve the resistance to chloride penetration into reinforced concrete. Corrosion inhibitors are generally divided into the anode-type inorganic inhibitors and anode-cathode-type organic inhibitors, in terms of the reaction type. It is known that when the Cl-:OH- concentration ratio exceeds 0.6%, film on passive state metal on the bar-concrete interface is damaged and local corrosion starts regardless of the chloride ion content. In this study, the performance of the corrosion inhibitor was examined using a potentiostat, with chloride ion contents of 1.2kg/m3 (as reference), 2.4kg/m3, and 4.8kg/m3. The variables were the inhibitor type, Cl-:OH- molar ratio according to the addition of anode-type inorganic corrosion inhibitor (four ratios: 0.0%, 0.3%, 0.6% and 1.2%), and ratio compared to the standard anode-cathode-type organic corrosion inhibitor liquid (four ratios: 0.0, norm 1/2, norm, norm 2 times). As a result, with the anode-type inorganic nitrite corrosion inhibitor, the corrosion inhibition performance was verified with a corrosion potential of -0.30V at a molar ratio of 0.3% or higher when the chloride ion content was 1.2kg/m3, and at a molar ratio of 0.6% or higher when the chloride ion content was 2.4kg/m3 or 4.8kg/m3. With the anode-cathode-type organic corrosion inhibitor, the corrosion inhibition performance was very good at half the standard quantity (0.42kg/m3) regardless of the chloride ion content. From the added corrosion inhibitor quantities, the anode-cathode-type organic corrosion inhibitor had a better corrosion inhibition performance than the anode-type inorganic nitrite corrosion inhibitor.

The various methods for improving chloride penetration resistance in the reinforced concrete have been developed. Among the related general ways, using of corrosion inhibitor became very common. Therefore, in this study, in order to comprehend performance of corrosion inhibitor, the experiment study was conducted about corrosion characteristic of 3 steps(0.0, norm 1/2, norm) compared to organic corrosion inhibitor standard use of liquid and molar 3 steps(0.0, 0.3, 0.6%) of Chloride by added amount of inorganic corrosion inhibitor by the corrosion inhibitor types about 2.4kg/m3, 4.8kg/m3based on Chloride ion content 1.2kg/m3for service life prediction of concrete structure by using Poteniostat. As results, in the case of inorganic nitrous acid corrosion inhibitor, it was confirmed that anti-corrosive performance of Chloride ion content 1.2kg/m3by corrosion Ecorr -0.30V in more than molar ratio 0.3%, and it also was confirmed that anti-corrosive performance of 2.4kg/m3, 4.8kg/m3in more than molar ratio 0.6%. In addition, the excellent anti-corrosive performance of organic corrosion inhibitor was shown in 1/2(0.42kg/m3) of norm regardless of Chloride ion content, and it can be seen that absorption types organic corrosion inhibitor has excellent anti-corrosive performance compared to the inorganic nitrous acid corrosion inhibitor by the added amount of corrosion inhibitor.

Corrosion sensors were devised to develop a system whereby the depth of chloride permeation from concrete surfaces can be monitored in cover concrete of reinforced concrete structures. For making sensor which is similar to rebar author uses Screen printer machines, Ag paste and Fe powder. Appropriate portion of Ag and Fe is over 1:2. The resistance of sensors increased as the degree of corrosion increased.

Concrete is a type of porous materials and is physically and chemically damaged due to exposure to various environments from the placing to the service life. These reactions affect the corrosion of steel bars applied in concrete and that decreases the durability life and strength of such steel bars. Thus, it is very important to insert rust inhibitors into steel bars in the case of a deterioration element that exceeds the critical amount of corrosion in the location of steel bars. However, it is very difficult to guarantee corrosion resistance at the location of steel bars using conventional technology that applies corrosion inhibitors only on the surface of concrete. This study attempts to develop a method that penetrates corrosion inhibitors up to the location of steel bars and investigate the penetration depth of corrosion inhibitors by verifying moisture migration in concrete under an applied pressure.

It is well known that carbonation will result corrosion of steel reinforcement in reinforced concrete structures. To reduce the rate of carbonation, the surface coatings, such as mortar finish, has been used widely to concrete. This paper presents a numerical procedure about carbonation of the coating-concrete system. This numerical procedure starts with a multi-component hydration model. By hydration model which considers both and Portland cement and pozzolanic reaction, the amount of hydration products which are susceptible to carbonate as well as porosity is obtained as function of age. Furthermore, the diffusivity of CO2 is determined and carbonation depth of concrete is predicted. Parameter studies are performed to show the influence of composition and application time of mortar finish on carbonation depth of substrate concrete.

Examination about sticking intensity security way of normal temperature metal spraying covering is required compulsorily accordingly with quantitative assessment about steel plate's surface roughness to secure adhesive power of steel materials and metal membrane stably at application of way method of construction by normal temperature metal spraying. In case of metal spraying, Sticking strength of metal spraying way finish is influenced greatly, and it is judged that is desirable that manages Sm/Rz by 6 lows to secure more than sticking intensity 20kgf/cm2 by Sm/Rz that evaluate that is rough of nature surface. The purpose of this study was to analyze an adhesion strength of metal spraying finish layer with the surface conditions of steel plate. For the purpose the experimental factors such as anticorrosive finish method and surface treatment method were selected.

Cathodic Protection Method was introduced as a corrosion protection method of metals under the ground or sea. Since 1970, it was applied to corrosion protection method of reinforced concrete structures. After 1990, this method has been used around the world, and its usability was proved. But this method has some problems on the aspect of construction and economy. In order to solve these problems, Cathodic Protection Method by using high durable metal spray was developed. First, the specimen was covered with anodic materials (Zn, Al) by using metal spray. And a performance of corrosion protection was confirmed by measuring corrosion current and halfcell potential of specimen. Through the result of experiment, it is possible to know that Cathodic Protection Method by using high metal spray is good protect to corrosion on reinforced concrete structures.

The purpose of this research is to evaluate the effectiveness of nitrate as a corrosion inhibitor in mortar containing chloride. In the experiment, test specimens of mortar to which chloride and nitrite had been added, were subjected to accelerated corrosion by means of repeated drying and wetting on condition of high temperature. This study concerns the assessment of the inhibition effect of nitrite-based corrosion inhibitor using a polarization method and its influence on the chloride transport, compressive strength and setting time of concrete. From the results of the experiments, it was confirmed that the lithium, calcium nitrite corrosion inhibitor and new corrosion inhibitor over dosage 0.6 (NO2-/Cl-) molar ratio is very effective in protecting reinforcement from corrosion in mortar in which chloride ions have contained.

Autogenous shrinkage is the term for the bulk deformation of a closed, isothermal, cement-based material system not subjected to external forces. It is associated with the internal volume reduction of cement/water mixture in the course of the hydration process. However, addition of blended components to cement, especially such as fly ash or silica fume, for the high-performance concrete will lead to a densification of the microstructure. The autogenous shrinkage deformation will increase and the following autogenous shrinkage crack will do harm to durability of concrete structure. In this paper, numerical simulation is suggested to predict autogenous shrinkage of high performance cement paste. The simulation is originated from a multicomponent hydration model. The numerical program considers the influence of water to cement ratio, curing temperature, particle size distribution, cement mineral components on hydration process and autogenous shrinkage. The prediction result agrees well with experiment result.

Where the self weight of the overall slab needs to be considered, the quantity of in-situ concrete required can be reduced by the introduction of polystyrene void forms supplied and fixed to the precast panel during manufacture. In this study, new I-slab system with polystyrene form and precast concrete deck is proposed to reduce the construction period and the self weight of the slab. This paper presents experimental works on the bending and shear of the I-slabs. Five specimens were tested. The main parameters of experiments were the hole diameter of polystyrene form and the thickness of slab. Structural performance of I-slab was evaluated on the basis of failure mode, load-displacement curve, and ultimate strengths. Based on the test results, the critical punching shear sections were changed as test variables, so the punching shear strengths were very different. Test results indicated that the developed I-slab were very effective to increase the strength because of self weight reduction.

This paper presents a model for chloride diffusion in cracked concrete. This numerical model includes two parts: hydration model and chloride diffusion model. The hydration model starts with mix proportion of concrete and considers both Portland cement hydration and pozzolanic activity. By hydration model, the evolution of properties of cement paste is described as function of curing age. Furthermore, based on general effective media theory and composite spheres assemblage model, the effective diffusivity of chloride ions in concrete without crack is obtained. Finally based on crack distribution in cracked concrete and finite element methods, the diffusion of chloride ions in cracked concrete is predicted. The prediction results agree well with experiment results.

Life span of structures made with concrete was shortened by carbonation. This phenomenon makes pH in concrete lower. If pH value in concrete become below 10, rebar in concrete begin to be corroded. This pH value was effected by quantity of Ca(OH)2 that depends on cement types, hydration reaction and carbonation time. In this study, pH value and quantity of Ca(OH)2 in mortar which has blast furnace slag were tested according to hydration and carbonation time. As a test result, the more cement has blast furnace slag (BFS) and the longer carbonation time last, the lower pH value in mortar has. And using this quantitative analysis result of pH and Ca(OH)2, it may be used effectively when service life considering carbonation is predicted using FEMA.

With the development of concrete industry, the necessity for utilizing waste materials and decreasing overall energy consumption is becoming increasingly obvious. Fly ash and granulated blast-furnace slag, which are used as blends of Portland cement, are waste materials produced in electric and energy industry, and concretes made with them can have properties similar to ones made with pure Portland cement at lower cost per unit volume. By using blended Portland cement, both ecology benefit and economic benefit can be achieved. Due to the pozzolanic reaction between calcium hydroxide and blended components, compared with ordinary Portland cement, hydration process of blended Portland cement is more complex. In this paper, based on a multi-component hydration model, a numerical model which can simulate heat evolution process of blended Portland cements is built. The influence of water to cement ratio, curing temperature, particle size distribution of cement paste and blended Portland material, and cement mineral components on heat evolution process is considered. The prediction result agrees well with experiment result.

Economic losses due to the corrosion of steel structures in concrete is almost about 4% of GNP. It is almost 70 billion dollars in America. Also, The Korean economy is expected to experience a 4～5% loss in GNP in the near future in by considering the industrial background that has been formed by heavy industries. Although deteriorations in concrete structures demonstrate a high diversity of factors, it finally comes down to the lowering of water resistance performance in structures based on the crack generation due to the corrosive expansion of steel bars. Thus, it is very important to investigate the lowering of water resistance performance in structures according to the level of the corrosion in steel bars.

A cement which is used in construction and a concrete which is a hydration product of cement is considered anti-environmental materials because of lots of CO2 emission in progress of producing and making them. But a concrete absorbs CO2 gas in atmosphere after hydration and in its lifetime. It is called carbonation. Based on Papadakis’ theses, this research is carried on calculation of the CO2 absorption quantity in concrete. After research, we calculated the CO2 absorption quantity in concrete which has various surface-finishes and we evaluate each surface-finishes the resistance against carbonation.

Chloride attacks concrete structures becoming a primary factor that deteriorates the durability of concrete structures. For this reason, research has been conducted on chloride ion penetration and diffusion. This research produced an accurate durability life prediction through reliability assessments and proposes a prediction method for the chloride ion diffusion coefficient of a concrete applied assessment program for reliability. As a result, test materials were fabricated using different admixtures and chloride ion diffusion coefficient was calculated by applying an RCPT test at each equivalent age. Based on these results, reliability prediction formulas were indicated through the reliability analysis for a durability life design using a Montecarlo method. In addition, propriety was verified through comparisons and analysis using the proposed formula with the investigated data for chloride ion diffusion.

This study performs an electrochemical experiment to quantitatively evaluate the corrosion resistance performance in a Zn-Al thermal metal spraying method and produces corrosion current density according to the type of corrosion resistance methods. In the results of the calculation, the corrosion membrane produced in a Zn-Al thermal metal spraying method showed voltage differences more than 300 mV and that demonstrated enough corrosion performance with the corrosion resistance reaction of base materials and proper Zn-Al ratio, such as 50:50. Also, the results exhibited that the corrosion speed in a Zn-Al thermal metal spraying method was 0.66 time faster than that of the zinc galvanizing method in the estimation based on the standard of corrosion resistance service years in a zinc galvanizing method (JIS H 8641).

This paper describes a numerical method for estimating the elastic modulus of cement paste. The cement paste is modeled as a unit cell, which consists of three parts: dehydrated cement grain, gel, and capillary pore. In the unit cell, the volume fractions of the constituents are quantified with a single kinetic function of the degree of hydration. The elastic modulus of cement paste was calculated from the total displacement of constituents when the uniform pressure was applied to the gel contact area in cement paste assumed a homogenous isotropic matrix. Numerical simulations were conducted through the finite element analysis of the three-dimensional periodic unit cell. The model predictions were compared with experimental results. The predicted trends agree with experimental observations. The approach and some of the results might also be relevant for other technical applications.

The purpose of this study is to define the amount of critical corrosion in steel that causes cracks on the cover of concrete. Major variables in the amount of critical corrosion are concrete strength, thickness, and the cover of concrete. In this experiment, stress concentration is a newly added factor. According to the results of this experiment, it is evident that the amount of critical corrosion decreased according to the increase in stress concentration factors. In addition, electric currents were measured using a constant voltage generator. When a constant voltage was connected to the corrosion circuits, it was discovered that the magnitude in the change was similar to the displacement on the cover of concrete and the electric current according to time.1)

As concrete is a type of porous materials, water or air freely permeates concrete. Therefore the durability of concrete decreases. However, porous material with a rust inhibitor may allow permeation of water into concrete. In addition, there may be permeation of water through the rust inhibitor at the location of steel frames. The objective of the study is to investigate the penetration depth of concrete under water forced conditions with pressure.

Recently, Reinforced Concrete(RC) is used in most buildings. However, steel bars in concrete cause corrosion through carbonation. Furthermore, corrosion shortens the life span of RC structures. Therefore, the surface-finishes such as restraint for penetration and diffusion of CO2 were used to lengthen the life span of RC structures. This study attempted to verify the restraining effect on a carbonation job according to the applied surface-finishes using an FEM analysis. This study also evaluated the restraining effect of carbonation on other surface-finishes with the process proposed in this study.

In this study, accelerated corrosion tests were conducted on concrete specimens with and without accelerated carbonation beforehand for the purpose of elucidating the effects of carbonation, cover depth, and water-cement ratio (W/C) on the reinforcement corrosion. During testing, the corrosion current between the anode steel and cathode stainless steel was measured to continuously monitor the progress of corrosion throughout the test period, thereby investigating the mechanism of reinforcement corrosion and the relationship between corrosion and crack width, as well as other parameters.

In recent years, the friction coefficient decline in the joints of steel structures caused by corrosion has drawn public attention. Therefore, this study investigated the friction coefficient and surface roughness of high tension bolt joints using a Zn/Al metal spraying corrosion resistance method to estimate the application possibility of the Zn/Al metal spraying corrosion resistance method on the joints of steel structures. According to results, the friction coefficient of Zn/Al metal spraying was 0.50 or more. In addition, the friction coefficient increased according to the decrease in surface roughness (Sm/Rz). Therefore, the Zn/Al metal spraying is applicable to a corrosion resistance method for high tension bolt joints.

As concrete is a type of porous materials, water or air freely permeates concrete. Therefore the durability of concrete decreases. However, porous material with a rust inhibitor may allow permeation of water into concrete. In addition, there may be permeation of water through the rust inhibitor at the location of steel frames. The objective of the study is to investigate the penetration depth of concrete under water forced conditions with pressure.

It is well known that PC (polycarboxylate) agent is superior to other agents for the early-strength of concrete. Thus, this study investigates the development of mortar strength using various agents. To prove this, various factors were tested. Furthermore, this study measured compressive strength at the age of 18, 24, 36, 72, and 168 hours and gave a request text TG/DTA to observe minute structures. In addition, this study took pictures of minute structures using an SEM for each agent at the same age. According to the results, mortar using an early-strength PC agents is faster than a general water reducing AE agent, high performance PC agents, and other agents in the acceleration of hydration at the same early age. A TG/DTA test shows that the early-strength PC agents create more hydration products, such as Ca(OH)2, than others at the same age. The degree of pH in each agent is unrelated to the degree of hydration in mortar. An MIP analysis confirms these results. However, other methods are required the exact analysis of micro structures.

RC beam with corroded tension rebars were strengthened with carbon fiber sheets(CFS) and were subjected to static loading tests to investigate the flexural strengthening effect of CFS. The test results confirmed that CFS are effective in reducing stresses to be carried by tension rebars and increasing flexural strength. Since the deformation capacity of the strengthened specimens was increased by anchoring the CFS and since the maximum strength of the specimens was determined by detachment or rupture of CFS, the flexural strength of the strengthened specimens could be calculated from an existing formula. Experimentally determined load-deflection relationships for RC beams were reproduced accurately through a FEM analysis modeling the bond elements between the concrete and the CFS. Practical application of the CFS sheeting method to RC beams requires improvement of the strength of bond between CFS and concrete.

In this study, an Ohno's anti-symmetric shear loading test was conducted after strengthening reinforced concrete (RC) beams damaged by corrosion of stirrup, with carbon fiber sheets (CFS) with a view to reviewing the effect of CFS on shear strengthening. As a result, it was found that CFS like stirrups could take shear stress, and that shear strength could be increased by using more CFS for reinforcement. It was also revealed that shear strength could be calculated by an existing evaluation equation by properly evaluating the effect of CFS on shear strengthening, based on the quantity of reinforcing CFS, ways of fixing the sheets and anchorage length as the effect on shear strengthening varied depending on the fixing method while sheet anchorage increased deformability.

This study was carried out to investigate quantitatively the relationship between the degree of reinforcement corrosion and the mechanical properties of reinforcement. In the experiment, the tensile test of corroded reinforcement was conducted at the different stage of the degree of reinforcement corrosion. As a result, it was found that the chloride-induced corrosion induce the pitting and the corrosion using electrical current induce the uniform corrosion. As the degree of reinforcement corrosion increased, the nominal yield point and nominal elastic modulus both decreased. Also, there were very high correlations between the degree of reinforcement corrosion and the mechanical properties of reinforcement. We could make the material constitutive laws for the mechanical properties of reinforcement as a function of the degree of reinforcement corrosion to analyze the damaged RC members with reinforcement corrosion using finite element method.

As most of the elementary, junior high, and high school buildings nationwide have been deteriorated since the quantitative increase of the buildings from 1985, many experts present the issues on the possibility of the structural instability of the building as well as the increase of the cost for maintenance of the building. So, it is necessary to examine the necessary structural information of the school buildings during the course of maintaining education facilities, and it is also necessary to establish some credible accessing procedures on the deteriorating school facilities so that the building structural engineers can propose the necessary standards for the proper maintenance and repairing works. To achieve the necessity, researches have been conducted to find out the ways of diagnosing the compressive strength and the durability of the concrete structures by measuring the compression wave velocity of concrete structures and the flaw detection inside the concrete specimens using the impact echo method, a non-destructive test to simulate the structures of school buildings. In this research, it was found that the impact echo method has great potentials in the application of the building structure maintenance and the repairing activities based on the accurate understanding of the existing school facilities that are being deteriorated. More over, school facilities has sometimes no structural design drawings available which NDT methods can contribute to detect the internal structural damages of existing building structures.

The present paper describes one of the most important slightly destructive technique used in the masonry survey: the flat-jack test. The test method is described in a critical way, emphasizing advantages and drawbacks. Besides, the relation between the flat-jack test and a numerical modelling is explored.