• Journal of the Korea Concrete Institute
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• v.11 no.3
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• pp.101-111
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• 1999

Compared with the BF slag, the EAF slag has expansion due to the reaction with water and free CaO. Therefore it is specified in Concrete Specification that the FAP slag aggregated must not be used in concrete. Because of this reason it is unusual to use the EAF slag aggregate in concrete. The EAF slag aggregate treated with accelerated and water aging was comparatively satisfied with fundamental properties, which are specific gravity, unit weight, abrasion and immersion expansion ratio, as concrete aggregate. Therefore when we measured the compressive strength till 28 days, we found that the mortar and concrete replacing the natural aggregate with the EAF slag aggregate by 4 steps had better results than the concrete using the natural aggregate in a view of the compressive strength. But at 91 days, concrete using the EAF slag aggregate had no difference with it using the natural aggregate.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.717-720
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• 2008

This study analyzed the basic characteristics and the characteristic of drying shrinkage and creep of high performance concrete complexly metathesized by BS and FA and the results are summarized as the followings. Regarding to the compressive strengths according to the passage of aging, OPC was appeared to be larger than B2F1 at the initial aging but B2F1 was appeared to be higher than OPC at aging 28days. Regarding to the changing rate of drying shrinkage according to the passage of aging, both OPC and B2F1 were appeared to be increased and, at aging 60days, B2F1 was appeared to be largely increased by about 42% as -21${\times}$10-6 및 -51${\times}$10-6 as compared to OPC. The transforming rate of creep was appeared to have been largely increased at the initial aging and then be smoothly increased somewhat as the aging was passed. And regardign to the transforming rate of creep after 60 days had been passed, B2F1 was appeared to be largely increased by about 13% as compared to OPC.

• Journal of Korean Society of societal Security
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• v.2 no.4
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• pp.59-65
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• 2009

The rebound test using Schmidt hammer is most popular method to estimate strength of concrete. However, this method is inappropriate for Seoul Metro underground structures due to unsuitable aging effects. Consequently, the strength presumption equation of underground structures is proposed according to the correlation of uniaxial compressive strength, rebound test results and age of concrete. To achieve this, the results of in-depth inspection of Seoul Metro underground structures performed annually for last 8 years was anlayed.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.275-278
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• 2000

In this paper, we carried out fundamental experiments to use steel manufacturing slag as a concrete aggregate. Generally, there are two types of slag, the blast-furnace slag and the steel manufacturing slag. The latter is classified by the difference of manufacturing method of steel into the convertor slag and the electric-furnace slag. The steel manufacturing slag mainly contains $SiO_2$ and CaO as the chemical composition. The reaction with water and a little of free CaO in the steel manufacturing slag made the expansion of volume change, Therefore, we primarily investigated physical properties, expansion mechanism, pH value, aging effect and aging methods in the steel manufacturing slag, Then compressive strength of concrete with steel slag aggregate is measured.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.997-1002
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• 2001

There are two types of chloride in concrete; one is added as concrete materials' chloride when concrete's mixing, and .the other is penetrated from the air and sea water in the sea-shore area. These chlorides penetrate into concrete, and they are accumulated inside the concrete with aging. This study aimed to evaluate the chloride ion penetration resistance of concrete containing GGBFS in the sea-shore area. Therefore, the specimens made with the replacement ratios(0, 0.30, 0.45, 0.60) of GGBFS were put into 3% NaCl solution according to the chloride accelerating test of JCI-SC3, and then investigated the weight changes, compressive strength, chloride ion with the depths of the specimens by aging. The result is that the diffusion coefficient of chloride ion is decreased with the increase of replacement ratios when compared to OPC

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.321-326
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• 2003

The nonlinear humidity distribution occurs due to the moisture diffusion when a concrete is exposed to an ambient air. These nonlinear humidity distribution induces shrinkage cracks on surfaces of the concrete. Because shrinkage cracks largely affect the durability and serviceability of concrete structures, the moisture diffusion in concrete must be investigated. The purpose of this paper is to propose a model of the moisture diffusion coefficient that governs moisture diffusion within concrete structures. To propose the model, numerical analysis were performed based on several experiments. Because the moisture diffusion coefficient is changed with aging, especially at early ages, the proposed model includes aging effect by terms of the porosity as well as the humidity of concrete.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.58-66
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• 1997

• Computers and Concrete
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• v.17 no.6
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• pp.703-721
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• 2016

A novel approach to modeling concrete behavior at the stage of its maturing is presented in this paper. This approach assumes that at any point in the structure, concrete is composed of a set of layers that are activated in time layer by layer, based on amount of released heat that is produced during process of the concrete's maturing. This allows one to assume that each newly created layer has nominal stiffness moduli and tensile/compressive strengths. Hence introduction of explicit stiffness moduli and tensile/compressive strength dependencies on time, or equivalent time state parameter, is not needed. Analysis of plain concrete (PC) and reinforced concrete (RC) structures, especially massive ones, subjected to any kind of straining in their early stage of existence, mostly due to external loads but especially by thermal loading and shrinkage, is the goal of the approach. In this article a simple elasto-plastic softening model with creep is used for each layer and a general layered model behavior is illustrated on one-dimensional (1D) examples.

• Journal of the Korea Institute of Building Construction
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• v.9 no.1
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• pp.81-87
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• 2009

The purpose of this study is to investigate the sulfate attack resistance of concrete using the EAF(electric arc furnace) Slag as fine aggregate. In order to figure out the effects of magnesium sulfate solution on the durability of concrete using the EAF Slag as fine aggregate, the experiments for the immerging test in the 10% magnesium sulfate solution was executed by selecting factors such as aging processes, replacement ratio(0, 10, 20, 30, 50%), and duration of immerging. The specimens were made with various EAF slag replacements for fine aggregates and with W/C ratio fixed 0.45. compressive strength and S.D.F(Sulfate Deterioration Factor), weight change, and SEM(Scanning Electron Microscope) were tested. From the test results, EAF slag aggregate treated with accelerated aging is better than treated with air aging. The compressive strength and resistance to the sulfate attack is slightly improved with an increase in the EAF slag aggregate treated with accelerated aging replacement for aggregate.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.947-952
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• 2001

The prediction model is proposed to estimate the variation of compressive strength of fly ash concrete with aging. After analyzing the experimental result with the model, the regression results are presented according to fly ash replacement content and water/cement ratio. Based on the regression results, the influence of fly ash replacement content and water/cement ratio on apparent activation energy was investigated. According to the analysis, the model provides a good estimate of compressive strength development of fly ash concrete with aging. As the fly ash replacement content increases, the limiting relative compressive strength and initial apparent activation energy become greater. The concrete with water/cement ratio smaller than 0.40 shows that the limiting relative compressive strength and apparent activation energy are nearly constant according to water/cement ratio. But, the concrete with water/cement ratio greater than 0.40 has the increasing limiting relative compressive strength and apparent activation energy with increasing water/cement ratio.