• Journal of the Korea Institute of Building Construction
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• v.10 no.3
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• pp.49-56
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• 2010

The purpose of this study is to examine the effect of variations in the mix rate of PVA fiber and the replacement ratio of non-sintering Hwangtoh on non-sintering Hwangtoh mortar and concrete mixed with PVA fiber. For water to binder ratio, mortar and concrete were both 50%, and PVA fiber mix rate was 0% and 0.3%. The replacement ratio of non-sintering Hwangtoh was 0, 25, 50 and 75(%) for mortar, and 0, 15, 30 and 50(%) for concrete. The properties of the mortar and concrete were compared and analyzed in 4 different levels, and the results can be summarized as follows. The replacement ratio of 30% of the non-sintering Hwangtoh, and the PVA fiber mix rate of 0.3% is determined to result in concrete of high quality, including strength and fluidity, and crack control by plastic shrinkage.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.499-506
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• 2014

A number of studies on eco-friendly and healthy building materials are being conducted as modern people are becoming more conscious about health and the environment they live in. Among those materials, studies on Hwangtoh are the most prevalent but due to its strength, crack coming from drying shrinkage, and susceptibility to water, the usage of Hwangtoh is incomplete and limited to be used as a common building material. Cement concrete, considered as one of the most widely used building materials, is extensively used in construction because it is economical, easily accessible and moldable and has proper compressive strength. Due to carbon dioxide created in the process of making cement concrete, it is recognized as pollution. Accordingly, there are a lot of studies on reduction of carbon dioxide in cement concrete industry. There are increasing numbers of researches as well as developments on Hwangtoh or traditional construction materials used in South Korea to reduce the environmental problems. Therefore, this study suggests the basic features of the construction material that can replace cement concrete in the future with the non-sindtered cement mixed with non-sintering hwangtoh which is made with the furnace slag and multiple stimulants.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.375-376
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• 2009

This study aims to provide basic material of concrete in replacement of non firing Hwang-toh, a traditional construction material in order to reduce CO$_2$ produced during manufacturing due to effectuation of the current Kyoto Protocol.

• 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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• 2021.11a
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• pp.34-35
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• 2021

In this study, we compared and analyzed hydration heat of the Concrete(NC) and non-fired Hwangto Concrete(HT). The Concrete(NC) was based on the mix that showed 30, 45 MPa on compressive strength on 28th and Only cement was used to make it. and We substituted 30% of weight of unit cement to non-fired Hwangto to create non-fired Hwangto Concrete(HT).

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.39-40
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• 2023

In this study, the compressive strength development was analyzed at early ages of concrete specimens admixed with non-sintered hwangto to reduce the CO₂ emissions generated during cement production. The W/B of the specimens was set at 0.41, the percentage of non-sintered hwangto admixture was set at three levels of 15, 30, and 45%, and the compressive strength were measured at 1, 3, 7, and 28 days. The results showed that the compressive strength decreases as the percentage of non-sintered hwangto increases, but the strength development rate increases, and the NHTC41-15 test specimen developed a compressive strength close to NC41 at 28 days.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.273-274
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• 2023

In this study, ultrasonic pulse velocity was analyzed to evaluate the high-temperature mechanical properties of concrete mixed with non-sintered hwangto. The W/B of the specimens was set at 0.41, the percentage of non-sintered hwangto admixture was set at two levels of 15,30%. The target temperature of the specimen is set to 6 levels of 20, 100, 200, 300, 500, 700 ℃, and the heating rate is set to 1℃/min. The result showed that the amount of non-sintered hwangto incorporated into the concrete tends to results in lower compressive strength. Ultrasonic pulse velocity showed similar trends, but differed in some areas.

• Journal of the Korea Institute of Building Construction
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• v.23 no.1
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• pp.35-43
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• 2023

In this study, the mechanical properties of concrete mixed with non-sintered hwangto(NHT) as an alternate material for cement were evaluated, and the compressive strength prediction equation of concrete based on ultrasonic pulse velocity analysis was proposed. Cement replacement rates for mixed NHT were set to 0, 15, and 30%, and design compressive strength was set to 30 and 45MPa to evaluate the effect on the amount of cement and NHT powder. The mechanical properties items analyzed were compressive strength, ultrasonic pulse velocity, and elastic modulus, and were measured on days 1, 3, 7, and 28. As the replacement rate of NHT increased, the mechanical properties tended to decrease. In addition, as a result of analyzing the correlation between compressive strength and ultrasonic pulse velocity, the correlation coefficient(R²) showed a high relationship(R²=0.95) on concrete mixed with NHT.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.159-160
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• 2023

Recently, interest in reducing cement has been growing. Hwangto, an eco-friendly material, has advantages such as air purification effect and humidity control, but when used, accidents such as form collapse may occur due to low strength and reduced durability. In order to quantitatively evaluate the timing of mold demolding, we would like to evaluate the timing of mold demolding through correlation with compressive strength using ultrasonic pulse velocity. As a result, the time at which 5 MPa is developed is after 20 hours for the test specimen of W/B 41 , in the case of W/B 33, NC33 and HTC33-15 were equally expressed at 12 hours, and HTC33-30 was expressed at 16 hours.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.105-111
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• 2023

In this study, the mechanical properties of high-strength concrete according to the substitution rate of NSH(Non-sintered Hwangto) as an alternative material for cement were measured and evaluated. Through UPV(Ultrasonic pulse velocity) analysis, the compressive strength prediction equation was proposed, and the substitution rate of NSH was set at 15 % and 30 %. The evaluation items were compressive strength and UPV, and the curing period was set to 24 hours. In compressive strength and UPV, as the NSH substitution rate increased, lower strength and lower UPV were shown. In addition, the correlation number(R² ) between compressive strength and UPV was 0.99 for NC(Normal Concrete), 0.97 for NSHC(Non-sintered Hwangto Concrete)33-15, and 0.94 for NSHC33-30.