• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.129-130
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• 2021

In order to solve the problem of low early-age compressive strength of high volume fly ash concrete. This paper studies the effect of 2% sodium sulfate (Na₂SO₄) as a chemical activator on the paste with 40% fly ash content and a water-binder ratio of 0.30. The results indicate that the addition of Na₂SO₄ can effectively improve the early-age compressive strength of the fly ash-cement system, and the strength improvement rate on the first day reached nearly 70%. In addition, calorimetric analysis reveals that the incorporation of Na₂SO₄ promotes the early hydration of cement and fly ash, increases the cumulative hydration heat and delays the heat peak of the aluminum phase.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.05a
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• pp.69-74
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• 2002

The following results are achieved from a mortar flow test depending on stainless steel slag fineness, replacement ratio, and a research on material age compressive strength, strength activity index. 1. Flow is proportional to the stainless steel slag fineness within the limits of 4000~8000$\textrm{cm}^2$/g, but in the case of fineness 20000$\textrm{cm}^2$/g flow decreases at all conditions except the case of replacement ratio 10%. 2. As stainless steel slag replacement ratio increases, Mortar of flow somewhat decreases. 3. As stainless steel slag blends, compressive strength decreases, but in proportion to the increase of age, compressive strength increases. 4. As stainless steel slag replacement ratio, compressive strength decreases. 5. In the case of stainless steel slag fineness 6000$\textrm{cm}^2$/g and 20.000$\textrm{cm}^2$/g, compressive strength of revelation ratio has the maximum value when it's replacement ratio is 10%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.75-76
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• 2017

In the case of B / a 1: 3, the intensity when the substitution rate increased to 15% showed a tendency to decrease, but it turned out that the strength increased at the substitution rate of 20%. In the case of B / a 1: 4 and 1: 5, it was found that when the substitution rate at the substitution rate of 10% was the highest and the substitution rate increased further, the strength was reduced. However, since the test body does not exist at the age of 3 days and the age of 7 days at the substitution rate of 0%, there is no specimen, so blast furnace slag binder substitution for increasing strength of refractory mortar is judged to be meaningless.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.132-133
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• 2018

The In this study, the change of composition of the hydrates according to the recovery age of concrete in the case of fire damage was confirmed through microscopic analysis. In 28 days of age, the production of ettringite was higher than that of day 1, and the calcium hydroxide was increased in the 91 day. It has been recovered through the generation of major hydrates which affect the strength.

• Journal of the Korea Institute of Building Construction
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• v.2 no.4
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• pp.163-168
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• 2002

The object of this study is to define the characteristics of high performance concrete with varing compressive strength of concrete and curing temperature. The major test variables are 1) high strength concrete(500kg/$cm^2$) and ordinary strength concrete(240kg/$cm^2$) compressive strength, 2) curing temperature and condition, 3) concrete curing age, 4) three types of cement. From the test results were shown that curing temperature and curing conditions were also very effective for high strength concrete and ordinary strength concrete, and concrete were largely effected by cement type and temperature during the hydration reaction process. This paper describes the effect of curing temperature for strength and characteristics of high performance concrete.

• Korean Institute of Interior Design Journal
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• v.21 no.1
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• pp.20-29
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• 2012

The study was intended to evaluate common spaces of office building in view point of universal design. The common spaces were access road, main entrance, parking lot, corridor, and restroom. Two office buildings in Centum city of Busan were evaluated by their workers, each 100 ones. The check list for evaluating them consisted of 36 universal design elements which related to five common spaces. First, there were many universal design elements which need to be improved. Second, among five common spaces, restroom has the most elements to be rated low. First of all, at least one restroom for wheelchair should be provided each floor. Third, even though both of two office buildings were recently built, there were significant difference between their users' evaluations. This implies that the concept of universal design is not applied to office buildings well. Fourth, there were significant difference among users' evaluations according to age, especially in case of design related elements. This means that users' age is an important factor to be considered.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.217-218
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• 2011

The advantages of blast-furnace slag concrete may include lower hydration heating velocity, restraint on concrete temperature increase, long-age strength improvement due to latent hydraulic reaction, improved water tightness, and repulsion to chemical erosion. These advantages contribute to the high quality of the blast-furnace slag concrete. However, the blast-furnace slag concrete has its limitations as well. These disadvantages may include retarded setting and elongated retention of mold due to the weak strength of early-age. Nevertheless, much research is currently under way to improve the aforementioned issues. To improve activity of blast furnace slag powder, alkaline irritants has been used. In this study, we analyze effect on activity fineness and rate of substitution of Alkali Activator toward activity.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.169-170
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• 2018

The purpose of the research is suggesting the temperature compensation strength for Unicode of constructure standard from Ministry of land, infrastructure and transport. As a result, for the concrete mixture with 100 % OPC, 6, and 3 MPa of compensating strength values were necessary when the temperature were from 4 to 9℃, and from 9 to 17℃, respectively. Additionally, when the temperature was higher than 17℃, compensating strength value was not necessary. In the case of 20 % of blast furnace slag replaced concrete mixture, 9, 6, and 3 MPa of compensating strength values were necessary when the temperature were from 4 to 6℃, from 6 to 12℃, and higher than 17℃, respectively.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.87-90
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• 2006

This study investigates the temperature history of slab mock-up specimens for hot weather concreting applying various surface insulating methods, in order to improve concrete quality at hot weather condition. Test showed that the use of insulating blanket or a bubble sheet on upper section of slab prevented from abrupt increase of temperature and vaporization of moisture during early curing at hot weather circumstance. In addition, it secured higher strength at early age. Therefore it is concluded that concrete construction insulating with the bubble sheet will reduce the plastic and drying shrinkage as well as improve strength at early age, thus securing concrete duality.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.101-105
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• 2009

The purpose of this study is to reduce autogenous shrinkage of high-strength concrete. Previous studies were investigated to measure the effects of reductions to autogenous shrinkage when applying bean oil to concrete. The results of the study showed that as the mixture rate of BO increased, fluidity decreased and air quantity decreased slightly. In early age, compressed strength increased compared to Plain while decreased in long-term age. As an autogenous shrinkage characteristic, reduction effect increased according to increase in mixture rate. When mixture rate is 1%, approximately 30% decreased compared to Plain in BO. At 2%, BO decreased by about 32%. In addition, in the case of BO, autogenous shrinkage was shown to decrease compared to expansive additive and shrinkage-reducing agent.