• Journal of the Korea Concrete Institute
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• v.12 no.4
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• pp.41-48
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• 2000

This study is to investigate for the frost resistance of high-strength concrete using finely ground granulated blast-furnace slag with experimental parameters, such as water/binder ratio, replacement proportion of granulated blast-furnace slag, air content and methods of curing. The high-strength concrete using granulated blast-furnace slag is effective to resist frost and decrease scaling. The more increasable replacement proportion of granulated blast-furnace slag is, the better the effect is. The high-strength concrete using granulated blast-furnace slag needs hydrating adequately to prevent deterioration by drying in the early curing period. The micro structure of high-strength concrete, increased to the pore number with diameter of 0.03~0.1mm, is changed by using granulated blast-furnace slag, but is presented differently according to water/binder ration and replacement proportion of granulated blast-furnace slag.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.33-36
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• 2005

Recently, the use of volcanic-ash as a part of cement content in concrete is very common. But, it has been indicated that the compressive strength of concrete using large amount of volcanic-ash as a part of cement content in early age is low and carbonation velocity is fast. To solve those problems, High Volume Volcanic-Ash Concrete which contained large amount of volcanic-ash as a part of fine aggregate has been proposed. This is an experimential study to compare and analyze the properties of High Volumn Volcanic-Ash Concrete according to the replacement method and ratio of volcanic-ash. For this purpose, the mix proportion of concrete according to the replacement method(PL, C10, C150, A10, A100, A150) And then slump, setting time, bleeding, compressive strength, tensile strength and carbornation test were performed. According to test results, it was found that the compressive strength of the concrete using the volcanic-ash as a part of fine aggregate(A) was higher than that of the concrete using the volcanic-ash as a part of cement content(C). And, the compressive strength of the A concrete increased in early age as well as in long tern age as the volcanic-ash content increased.

• Advances in concrete construction
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• v.12 no.5
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• pp.367-375
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• 2021

This study experimentally investigated the improvement of bond strength and durability of concrete containing high volume fly ash. Concrete mixtures made with 0%, 25% and 60% replacement of cement with class F fly ash were prepared. Water-binder ratios ranged from 0.28 to 0.72. The compressive, flexural and pullout bond strength, the resistance to chloride-ion penetration, and the water permeability of concrete were measured and presented. Test results indicate that except for the concretes at early ages, the mechanical properties, bond strength, and the durability-related chloride-ion permeability and water permeability of concrete containing high volume (60% cement replacement) fly ash were obviously superior to the concrete without fly ash at later ages of beyond 56 days. The enhanced bond strength for the high volume fly-ash concrete either with or without steel confinement is a significant finding which might be valuable for the structural application.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.507-512
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• 2002

Prestressed concrete I-girders were used in the bridge applications in the early 1950s. During the last four decades, the most widely used girder length of bridges have been below 30 meters. The main objective of this study is to develope the alternative section for widely spaced girder of 30 meters span bridge. Girder spacing, the number of strands and compressive strength of concrete are major parameters for widely spaced girders. The optimal girder spacing is determined through the parameter studies of design using widely spaced girders. 30m span bridges of widely girder spacing must use high-strength concrete. Although the basic unit cost of concrete is higher for high-strength concrete, it may be partially or even fully offset by reduced quantities of concrete as result of the smaller number of girders used. High-strength concrete girders have more prestressing strands per girder, but the total number of strands for all of the girders is less than that required for the larger number of normal-strength concrete girders. It could design PSC-I Birdge with widely spaced girder owing to high-strength concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.325-328
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• 2008

Recently increasing interest in high-rise building around the world for more than 100 floor, the trend is the increasing use of high-strength and high-flowable concrete so as of productivity improvements and cost savings to improve the performance of the early strength development. This study is to reach the optimal combination by reviewing the performance of high-rise building which is required. The results, lower the ratio of W/B was an increase in compressive strength and early strength in the use of admixture decreased in the combination of higher replacement ratio of admixture.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.266-267
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• 2014

In order to develop concrete generating compressive strength of 10MPa~15MPa aging for 6hours in the room temperature curing, Hardening accelerator containing Ca²⁺ mixed with rapid hardening portland cement containing C₃S in quantity. The result was that the more addictive contents of Hardening accelerator is, the more greatly early compressive strength was improved. That's because the composition of Ca(OH)₂ was mass-produced at early-ages.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.19-22
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• 2003

This study is carried out (1) checking the development of compressive strength of high flowing concrete at early age, changing water-binder ratio, curing temperature, and type of aggregate, and (2) suggesting basic date that helping cost and schedule plan in future construction. As the result of this study, we find that high curing temperature is effective for the development of compressive strength of concrete at early age on the condition of each water-binder ratio, and after making the compressive prediction formula related to the curing temperature by maturity, the result of the formular is similar to the temperature-compressive strength-age measured data

• Earthquakes and Structures
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• v.7 no.4
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• pp.527-552
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• 2014

The development of modern concrete technology makes it much easier to produce high-strength concrete (HSC) or ultra-high-strength concrete (UHSC) with high workability. However, the application of this concrete is limited in practical construction of traditional reinforced concrete (RC) structures due to low-ductility performance. To further push up the limit of the design concrete strength, concrete-filled-steel-tube (CFST) columns have been recommended considering its superior strength and ductility performance. However, the beneficial composite action cannot be fully developed at early elastic stage as steel dilates more than concrete and thereby reducing the elastic strength and stiffness of the CFST columns. To resolve this problem, external confinement in the form of steel rings is proposed in this study to restrict the lateral dilation of concrete and steel. In this paper, a total of 29 high-strength CFST (HSCFST) columns of various dimensions cast with concrete strength of 75 to 120 MPa concrete and installed with external steel rings were tested under uni-axial compression. From the results, it can be concluded that the proposed ring installation can further improve both strength and ductility of HSCFST columns by restricting the column dilation. Lastly, an analytical model calculating the uni-axial strength of ring-confined HSCFST columns is proposed and verified based on the Von-Mises and Mohr-Coulomb failure criteria for steel tube and in-filled concrete, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.469-470
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• 2010

The high-strength concrete(HSC) compared to normal concrete represents higher autogenous shrinkage due to lower water-to-binder ratio(W/B) and supplementaries, fly ash(FA) and granulated blast-furnace slag(BFS), etc. The potential of early age cracking which reduces durability of concrete structures is normally influenced by autogenous shrinkage and degree of restraint. Therefore, this paper studies on the evaluation of the characteristics of autogenous shrinkage for HSC, ultra-high-strength concrete(UHSC) containing admixtures by experimental test and the test results are compared with existed prediction models.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.601-604
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• 2008

This study as using admixture (G), high early strength agent, calcium hydroxide {a(OH)2} and fine particle cement, etc which have been newly developed for the purpose of quality improvements like the improvement of early strength of concrete that the FA was substituted by 20%, etc, reviewed the possibility of the utilization in the great quantity and the results are summarized as the followings. Slump loss by the kind of mixing material of high early strength agent and Ca(OH)$_2$ showed the smaller width of decrease than that of plain to appear the improved results and fine particle cement and G admixture showed the large slump loss. Air contents were appeared to satisfy the target air contents at all mixing materials. Regarding the compressive strength of the concrete by the kind of mixing material, G admixture was appeared to be highest all on aging 3 days, 7days and 28days at the initial strength. And fine particle cement and high early strength agent showed higher strength increase rate on aging 3days than plain but showed that the increase of strength becomes gradually dulled as aging is increased. And Ca(OH)$_2$ had almost no effect.