• Journal of the Korea Concrete Institute
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• v.13 no.2
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• pp.123-129
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• 2001

Pozzolan is to improve the strength and the durability of concrete as a result of the pozzolanic reaction, Broadly speaking, pozzolanic materials can be artificial materials, such as slica fume and fly ash, and natural material, such as rice husk ash, clay, volcanic ash, clayish pozzolan. Hwangtoh is a mineral which belongs to a group of matakaolin, especially halloysite, and the main elements is SiO$_2$, Al$_2$O$_3$, Fe$_2$O$_3$. The purpose of this study is to examine the application of Hwangtoh for the concrete admixtures, the composition of this study is shown as follows. Chapter I is analysis for properties of concrete as the kinds of admixture, and Chapter H is analysis for properties of concrete as the replacement ratio of activated Hwangtoh. As a result of this study, Hwangtoh is found to have high practical use as pozzolanic material, and the pertinent range of replacement ratios of Hwangtoh on cement are 10∼20 %.

• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.685-694
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• 2010

As a eco-friendly material, Hwangtoh (red clay) has been studied for complete or partial replacement of portland cement. Most of existing studies focused on the material properties of the Hwangtoh concrete including the compressive strength, drying shringkage, and creep. In the present study, the shear strength of the beams made with the Hwangtoh concrete was tested. Further, bond strength of tension re-bars embedded in the Hwangtoh concrete was tested. One of the concrete tested consisted of activated Hwangtoh replacing 20% of the cement. The other consisted 100% activated. Hwangtoh replacing all the cement. The beam specimens were tested under two point static loading. The test result showed that the shear strength of activated Hwangtoh concrete beams replacing 20% and 100% of cement was equivalent to that of the ordinary portland cement concrete beam. However, the bond strength of activated Hwangtoh concrete replacing 100% of the cement was less than that of the ordinary portland cement concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.797-800
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• 2008

To decrease the usage of cement, the pozzolan reaction materials are used as a mineral admixture. Hwang Toh which is broadly deposited in Korea is well known as a environment friendly material and the activated Hwang Toh which has the property of pozzolan reaction is practically used as a mineral admixture of concrete. PET fiber which is made by recycled PET bottle controls micro crack in concrete. But the study about concrete mixed with reinforcing fiber is not enough and the property of Hwang Toh concrete mixed with PET fiber is more complicated case. So this study performed drying shrinkage experiment to analyse mechanical property of Hwang Toh concrete mixed with PET fiber.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.567-574
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• 2010

As a eco-friendly material, Hwangtoh(red clay) has been studied for a partial or complete replacement of portland cement. Most of existing studies focused on the mechanical properties of the Hwangtoh concrete including the compressive strength, drying shrinkage, creep. In the present study, the flexural capacity of the beams made with the Hwangtoh concrete was tested. One of the concrete tested consisted of activated Hwangtoh replacing 20% of the cement. The other consisted 100% activated Hwangtoh replacing all the cement. The simple beams were tested under two point static loading. The flexural strength, cracking moment, deflection, and ductility were compared with those of the beams made with ordinary portland cement concrete.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.265-273
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• 2009

There have been numerous studies to develop eco-friendly concrete. The attempt to reduce the amount of cement used is suggested as one of the solutions for eco-friendly concrete. To decrease the usage of cement, the pozzolan reaction materials are used as a mineral admixture. Hwang-toh, which is broadly deposited in Korea is a well known environment friendly material and the activated hwang-toh, which has the property of pozzolan reaction, is alternatively used as a mineral admixture of concrete. The purpose of this study is to investigate the drying shrinkage of hwang-toh concrete mixed with recycled PET fiber. Therefore, drying shrinkage experiments are performed to analyze mechanical property of hwang-toh concrete mixed with recycled PET fiber. Test results showed that the drying shrinkage is controlled by hwang-toh admixture and PET fiber.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.6
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• pp.120-127
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• 2016

Several problems including respiratory and skin disorders due to the problems for sick house syndrome have occurred, there appears echo friendly materials to solve the problems. The research is lacking in quality management techniques ocher concrete using nondestructive tests. In this research, the experimental works were conducted to study the initial quality control for the compressive strength of Ocher concrete(21 MPa). The purpose of this study is the implementation platform for quality management of ocher concrete using nondestructive tests. It uses the relationship between the compressive strength and ultrasonic pulse velocity of the ocher concrete to estimate the compressive strength of the ocher concrete. And using the impact echo method to estimate the thickness of the ocher concrete. The platform is based on a Java script, so that the user can obtain the data through the platform.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.281-284
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• 2008

Recently, interest in eco-friendly structure has been increased and many researches about hwang-toh are being actively processed. However, most researches are about material properties of hwang-toh, and researches about structural performance are insufficient. Moreover, the usability of activated hwang-toh is being identified in some ways, but its use rate is low in economic aspect in reality. Non-activated hwang-toh is expected to be advantageous in respect of economy but its material and structural performance have not been identified. Therefore, the effect of activated hwang-toh and non-activated hwang-toh on flexural capacity of hwang-toh concrete beam is analyzed in this research.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.619-626
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• 2008

There have been numerous studies to develop eco-friendly concrete. The attempt to reduce the amount of cement usage is suggested as one of the solutions for eco-friendly concrete. To reduce the amount of cement usage, the pozzolan-reaction materials such as ground granulated blast furnace slag, fly ash, and meta kaolin are widely used as the mineral admixture. Hwangtoh which deposited broadly in Korea is a well known eco-friendly material and the activated Hwangtoh with pozzolan-reaction can be practically used as a mineral admixture of concrete. Meanwhile, PET fiber made of recycled PET bottle is a type of recycled material, which can be used to control micro cracks in concrete. But the study about concrete mixed with recycled PET fiber is insufficient and the research of Hwangtoh concrete mixed with PET fiber is urgently needed presently. In this study, experiment and analysis flexural behavior of Hwangtoh concrete blended with recycled PET fiber are carried out. The results are discussed in detail.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.152-159
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• 2010

Recently, the public interest in eco-friendly material and structure has been increasing and many Hwang-toh researches are being actively performed. Hwang-toh is one of the traditional environment friendly construction materials used as a construction and plastering material. Hwang-toh has many advantages as construction material due to its high heat storage capacity, auto-purification, antibiotic ability, and infrared ray emission characteristics. But, currently it has not been developed into construction material and used in modern construction due to its low strength and dry shrinkage cracking prone characteristics. According to the recent researches and study results, Hwang-toh can be used as a natural pozzolanic material like fly-ash or pozzolan. In this study, mechanical properties and structural flexure behavior experiments of slag, recycled PET fiber, and Hwang-toh added concrete are carried out. The test results showed that drying shrinkage of concrete mixed with Hwang-toh has lower compressive strength and elastic modulus than those of control cement concrete specimen, but it has the similar flexural behavior in reinforced concrete beams.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.549-555
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• 2008

In this paper, the applicability of Hwangtoh, as an alternative of cement paste, is investigated for the solution of internal heat and shrinkage caused by the hydration of cement paste. Several small-sized specimens of Hwangtoh and ordinary portland concrete (OPC) were compared as to compressive strength, heat of hydration, and shrinkage strain. Moreover, the applicability to the construction structures was reviewed through the test of large-size specimens. The 28-day compressive strength of Hwangtoh concrete (HBC), ranged 18 to 33 MPa, can reach that of OPC. Not only the maximun internal temperature of HBC was read about 1/4 of OPC as it is cured, but also its shrinkage decreased more than the OPC did. Therefore, Hwangtoh binder is more favorable than cement binder in terms of its hydration heat and shrinkage under the construction of concrete.