• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.795-798
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• 2002

Recently. the properties of early-age concrete are increasingly important because these properties directly influence the behavior of early-age concrete structures including stress and cracking behavior. Nevertheless, the studies on early-age concrete are limited to strength and temperature development. The purpose of present study is to propose a simple and rational method which can predict the stress and strain behavior of young age concrete. A series of test have been done to measure the temperature development, strains and stresses in concrete members. The concept of equivalent age was used to define the degree of hydration and this degree of hydration was used to calculate the strength and elastic modulus. The present study indicates that the calculated stresses correlate fairly well with measured stresses. The consideration of critical degree of hydration in calculating stresses gives more accurate results. The present study provides useful method and data in evaluating early-age behavior of concrete structure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.75-78
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• 2005

This raper investigates the effect of curing temperature on strength development of concrete incorporating cement kiln dust(CKD) and blast furnace slag (BS) quantitatively. Estimation of compressive strength of concrete was conducted using equivalent age equation and rate constant model. An increasing curing temperature results in an increase in strength at early age, but with the elapse of age, strength development at high curing temperature decreases compared with that at low curing temperature. Especially, the use of 35 has a remarkable strength development at early age and even at later age, high strength is maintained due to accelerated pozzolanic activity resulting from high temperature. Whereas, at low curing temperature, the use of BS leads to a decrease in compressive strength. Accordingly, much attention should be paid to prevent strength loss at low temperature. Based on the strength development estimation using equivalent age equation, good agreements between measured strength and calculated strength are obtained.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.63-71
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• 2010

This paper is about a research of steam curing which is one of the curing methods for accelerating the early-age strength of pre-cast concrete. With cylinder mold and mock-up specimen, the research was executed to study the best cycle of steam curing temperature through quantifying cycle of steam curing and maximum temperature, while the required strength is developed under the early-age. Moreover, causes and measurements for the high temperature of concrete, which is due to the steam curing, and the crack, which occurs when removing steel form, are stated. Ultimately, the economical method of producing, which satisfies early-age strength development and quality assurance while manufacturing PC structure, is stated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.409-410
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• 2023

In this study, the compressive strength and ultrasonic pulse velocity were evaluated according to the elapsed time on concrete mixed with normal and lightweight aggregates at early age. For evaluation in various strength ranges, the design compressive strength was set to 30, 45, and 60MPa and evaluated. As a result of the experiment, the compressive strength of concrete mixed with lightweight aggregates developed 5MPa earlier compared to normal aggregate concrete, and the UPV showed a similar tendency.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.2
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• pp.191-197
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• 2001

In this study, the admixtures for agents for enduring cold weather used widely are collected and applied to cement mortar to analyze the strength development due to variation of curing temperature at early age. The test results show that anti-freezing admixture have some problems due to high chloride content, which may cause the corrosion of reinforcement embedded in concrete. However, the mortar applied by accelerator and another kind of agent for enduring cold weather produced by S company lead to delay of strength development in low temperature. Also, it is clarified that there are no significant problems for cement mortar in strength development due to low temperature if a suitable kind of agent enduring cold weather is used and cement mortar is cured for more than $7.5^{\circ}D.D$ at early age.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1215-1220
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• 2000

Blast-Furnace Slag, a by-product of the iron or steel industry, has potential sa a cementitious material. The addition of a Blast-Furnace Slag generally reduces the heat of hydration and can confer significant improvements in resistance to sulfate attack and alkali-aggregate reaction, as well as increases in ultimate strength. But it also reduces early-age strength. In this study, for the purpose of improvement of early-age quality of Blast-Furnace Slag concrete, we choose blaine fineness of $6, 000~8, 000cm^2/g$ of Blast-Furnace Slag, and investigate the various properties of concrete. As a result, workability and early-age strength of Blast-Furnace Slag concrete were improved according to the increase of blaine fineness of Blast-Furnace Slag.

• Journal of the Korea Institute of Building Construction
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• v.7 no.4
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• pp.145-151
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• 2007

In this paper, tests are carried out in order to investigate the strength development of concrete under various binder types, W/B and curing temperature ranged from $5{\sim}20^{\circ}C$. Fly ash and blast furnace slag were incorporated by as much as 30%, respectively. Strength development of concrete are estimated using Logistic model and strength ratio of concrete at 28days to that at early age are also investigated. According to experimental results, it is found that good agreements are obtained between measured values and calculated ones using logistic model below $20^{\circ}C$. Strength ratio of concrete at 28days to that at early age increases in case W/B decreases and curing temperature increases. Tables and graphs for strength ratio of concrete are provided in this paper. It is capable of obtaining and predicting the periods to attain design strength by considering increment factor of strength easily with the table and graphs presented in this paper. This paper presents the reference data to decide removal time of form, time to reach target strength and strength inspection of remicon whether the test specimens meet the specified criteria of compressive strength. Multi regression models with respect to the relationship between 7days compressive strength and 28 days compressive strength depending on W/B and admixture types are presented.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.889-892
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• 2006

In this study, we compared and analysed the early strength properties of mortar according to the kinds and replacement ratio of mineral admixture to select the kinds and replacement ratio of mineral admixture of high early strength concrete. For this purpose, mortar mixtures according to the kinds(FA, MK, ZR, BFS, DM) and replacement ratio(0, 2, 4% by volume of sand) of mineral admixture were selected. From our test data, early-age compressive strength decreased in accordance with the increase of replacement ratio of fly-ash(FA) & blast furnace slag powder(BSF) and, in case of addintion admixture, early-age compressive strength of with containing ZR & BFS appeared higher compared with containing other mineral admixture.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.47-55
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• 2000

Protections from the frost damage at early ages are one of the serious problems to be considered in cold weather concreting. Frost damage at early ages brings about the harmful influences on the concrete structures such as surface cracks and declination of strength development. Therefore, in this paper, protecting periods of frost damage at early ages according to the standard specifications provided in KCI(Korean Concrete Institute) are suggested by appling logistic curve, which evaluates the strength development of concrete with maturity. W/B, kinds of cement and curing temperatures are selected as test parameters. According to the results, the estimation of strength development by logistic curve has a good agreement between calculated values and measured values. As W/B and compressive strength for protecting from frost damages at early ages increase, it is prolonged. It shows that the protecting periods of FAC(Fly Ash Cement) and BSC(Blast-furnace Slag Cement) concrete are longer than those of OPC(Ordinary Portland Cement) concrete. The protecting peridos from frost damage at early age by JASS are somewhat shorter than those by this paper.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.48-49
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• 2013

This test investigates early strength and durability of concrete using early strength type materials(cement, Polycarboxylate acid). The goal of this test is to secure the strength of 5.0 MPa in 12 hours early age and strength of 14 MPa for 24 hours correspondingly. This type of admixtures, concrete curing temperature, amount of binder and other concrete properties were confirmed by experimental factors. Comparing outcomes from two cases on using early strength type materials and common materials resulted in reducing of costs and shortening of the construction period, that determined the economical benefits of using early strength materials in construction.