• 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.

• Journal of the Korea Institute of Building Construction
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• v.8 no.3
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• pp.111-117
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• 2008

This study provides the setting time prediction method of super retarding concrete incorporating mineral admixtures at the same time including fly ash(FA), blast furnace slag(BS) based on maturity method. The setting time was retarded, as super retarding agent contents increase and curing temperature decreases. In addition, apparent activation energy by Arrhenius function was ranged from $24{\sim}35KJ/mol$ with slightly difference along with mixture proportion. This value is smaller than existing value $30{\sim}50KJ/mol$. It is Indicated that equivalent age using setting time can be a proper method to predict setting time and it also exhibited comparable relativity between prediction value and measurement value. Therefore, this study provided setting time prediction value with super retarding agent contents and mineral admixture combination. Setting time prediction equation provided herein is possibly valid for estimating precise setting time of the super retarding concrete at the job site.

• Journal of the Korea Institute of Building Construction
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• v.14 no.3
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• pp.273-284
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• 2014

Ultra-high-performance concrete (UHPC) consists of cement, silica fume (SF), sand, fibers, water and superplasticizer. Typical water/binder ratios are 0.15 to 0.20 with 20 to 30% silica fume. In the production of ultra-high performance concrete, a significant temperature rise at an early age can be observed because of the higher cement content per unit mass of concrete. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of ultra-high performance concrete. The heat evolution rate of UHPC is determined from the contributions of cement hydration and the pozzolanic reaction. Furthermore, by combining a blended-cement hydration model with the finite-element method, the temperature history in the hardening of UHPC is evaluated using the degree of hydration of the cement and the silica fume. The predicted temperature-history curves were compared with experimental data, and a good correlation was found.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.135-136
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• 2014

In this study, the experimental study on the early age compressive strength of cement mortar using anti freezer and hardening accelerator at low temperature was conducted. For this study, all of materials for experiment were kept in a low temperature for 24 hours before mortar mixing. After mortar curing at low temperature, compressive strength was measured at the early ages. Furthermore, properties of hardened cement material was analysed using TG-DTA and MIP.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.107-110
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• 2009

After inquiring into physical characteristics of using fly ash and alkali solution, it was found that higher pH density is favorable to strength development at early age and the higher the age is, the higher the compressive strength gets. Also, it was found that when there is more addition of activator, the compressive strength is higher. I was shown that more than atmospheric curing, steam curing was favorable for development of compressive strength. When the temperature of curing temperature was higher, most of the compressive strengths were higher. Thus, based on this study, it was understood that environmental-friendly chemically combined concrete using fly ash and alkali solution can be utilized without using cement.

• 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.

• Journal of the Korea Institute of Building Construction
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• v.3 no.3
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• pp.121-126
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• 2003

This study investigated about several mix factors came up to drying shrinkage and carbonation of high flowing concrete using viscosity. The results are as follows; Drying shrinkage ratio of high flowing concrete using viscosity showed higher for early age, but lower than normal concrete as long age. Also, drying shrinkage ratio and reduction ratio of mass showed higher and relative dynamic modulus of elasticty showed lower as W/C was higher generally. And in case of high flowing concrete using viscosity, carbonation wasn't confirmed without the kinds of cement and viscosity except 50C.

• 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.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.45-46
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• 2022

In this study, ultrasonic pulse velocity is compared on non-sintered hwangto concrete(NHTC) and normal concrete(NC) at ages. Strength of specimens set up 30MPa. Cement is replaced with 15 and 30% non-sintered hwangto. UPV is tested at 1, 3, 7, 28, 56, 91 days. As a result, UPV increases as the age and strength increase, but decreases as the non-sintered hwangto replacement increases. Although ultrasonic pulse velocity of NHTC was 72% lower than NC, after that, difference tends to decrease

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.231-232
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• 2021

This study intended to verify the alkali activation effect of concrete by replacing FA and CBS-Dust with cement to find out how to utilize CBS-Dust generated during cement production. Experiments result shows that air flow and liquidity can be secured when CBS-Dust is replaced by 5% in FA 20%, and that relatively high compressive strength is expressed in the initial age of 3 days and 7 days and long-term age of 91 days.