• Journal of the Korea Institute of Building Construction
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• v.12 no.5
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• pp.468-477
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• 2012

This study aimed to mix and test mortar incorporating activated Hwangtoh to improve the Hwangtoh brick bond strength of brick structures. To do this, the bond strength correlation of mortar was analyzed by means of materials and experiment factors and levels, and the optimum conditions were suggested after analyzing the physical properties of brick and the mix ratio of mortar and additive. Furthermore, the compressive strength and bond strength were found to be in inverse proportion, and in terms of the materials and mixing level, W/C ratio, substitution ratio of activated Hwangtoh, and fine aggregate grading were shown to have a considerable influence on the strength. In conclusion, the optimum mixing conditions to improve the bond strength are found to set W/C ratio at 65% and replacmenet ratio of activated Hwangtoh at 10%.

• Journal of Korean Society of Rural Planning
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• v.11 no.3 s.28
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• pp.53-57
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• 2005

Up to recently building are constructed focusing on the convenience of residential condition. However, environmental-friendly materials is required for construction as people are spending more time inside buildings and causes of many problems like sick-building syndrome are known due to the noxious gases and polluted air originated from construction materials. Although loess(hwangtoh) is an environmental-friendly material, it has limitations in compressive strength far a construction material. The purpose of this study is to suggest the optimal ratio of loess(hwangtoh) mortar by tests of compressive strength comparing with standard strength of floor finishing mortar and evaluate the usability of loess(hwangtoh) mortar for floor finishing material through an impact test, a cracking test and a abrasion test. Based on the results of this study, 86% of loess(hwangtoh) and 14% of inorganic binder is suggested for the optimal mixture ratio of loess(hwangtoh) mortar. Moreover, the characteristics of loess(hwangtoh) is suitable for floor finishing material in impact, crack, abrasion.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.173-176
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• 2002

This study is performed to examine the dry Hwangtoh mortar. The unit weight is in the range of $1,891kg/m^3{\sim}2,037kg/m^3$, it tend to decrease with increase using the Hwangtoh. The compressive and bending strength are in the range of $105kgf/cm^2{\sim}353kgf/cm^2,\;18kgf/cm^2{\sim}66kgf/cm^2$, respectively. The mortar of using Hwangtoh 20% is showed the highest strength ratio.

• Journal of the Korea Institute of Building Construction
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• v.12 no.3
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• pp.332-339
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• 2012

In this study, six mortar mixes were tested in order to examine the significance and limitations of hydrophilic fiber in terms of its capacity to enhance the tensile resistance of Hwangtoh mortar. Lyocell, polyamide and polyvinyl alcohol (PVA) fibers were selected for the main test parameters. The tensile capacity of mortars tested was evaluated based on the splitting tensile strength and the modulus of fracture, while their ductility was examined using the toughness indices specified in ASTM. Test results showed that the addition of lyocell and PVA fibers had little influence on the flow of the Hwangtoh mortars. To enhance the tensile capacity and toughness index of Hwangtoh mortar, it is proposed that fiber spacing above 0.0003 is required, regardless of the type of fiber.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.43-46
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• 2006

The Hwangtoh is one of the traditional construction material used in wall, plastering material, and ondol (Korean underfloor heating system) with stone and wood. It is an important greenness material and it has much advantages such as; high storage of heat, auto-purification, antibiotic ability, and emission of far infrared rays. But, it is not developed and not used in modern construction because of its low strength and properties of dry shrinkage crack. According to the recent researches and studies, it is evaluated for natural pozzolanic material like flyash or pozzolan. It's possibility on construction material is high because it's chemical and mineralogical proportion is like as Metakaolin and Kaolinite. In this point of view, this study aims to analyze the physical properties on Hwangtoh mortar through an experiment with various activation condition of Hwangtoh, which is natural pozzolanic material, for the purpose of increase the using possibility in construction material.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.506-513
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• 2020

In this study, the mechanical properties, absorption, and reduction performance of NOx in the mortar containing mineral admixture like zeolite and active hwangtoh were evaluated. Zeolite and active hwangtoh were used as binder, and zeolite and active hwangtoh were substituted for cement. The substitution ratio of two types of mineral admixtures was considered as 20 and 30% respectively. As a result of evaluating the compressive strength and flexural strength of each mortar specimen, the highest strength in the plain mixture was evaluated. As the substitution ratio of zeolite and active hwangtoh increased, the compressive and flexural strength decreased. In addition, the difference of compressive and flexural strength between active hwangtoh and zeolite mixing was evaluated to be insignificant. To evaluate the absorption rate, the mixture was designed to lower the W/B ratio of the existing mixture and set the substitution ratio of active hwangtoh and zeolite at 25%. The highest absorption ratio in the mortar with zeolite was evaluated, and the difference in absorption ratio between the remaining two mortar mixtures was small. The assessment of reduction performance of NOx considering the application of photocatalyst showed a clearly decreasing reduction behavior, even if they were the same mortar mixture. Zeolite and active hwangtoh also showed a higher NOx reduction than the Plain mixture, because of their porosity properties. In the case of active hwangtoh, the absorption ratio was lower than that of zeolite mixture, but the reduction of NOx performance was better than the result of zeolite mixture.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.520-527
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• 2020

Hwangtoh is the rich resource that accounts for about 15.0% of the domestic soil, and can be used as the admixture of concrete with Pozzolan characteristics if activated by rapidly freezing after burning with high temperature. In this study, the mortar curbs containing active hwangtoh were produced, based on the mixture for the mortar curbs sold on the market. The substitution rate of active hwangtoh were considered 10.0% and 25.0%, and the test items were selected to compressive and flexural strength tests, freezing/thawing resistance tests, accelerated carbonation tests, and accelerated chloride diffusion tests. In the results of the mechanical performance, it was showed that the highest strength was evaluated in OPC mixture, and the increase in strength was small by the increase of age, which was believed to be due to the fact that most of the strength in each mixture was created in three days of steam curing. The results of the freezing/thawing tests for 28 aged days showed the reduction rate of compressive strength was 85.0% or higher for all specimen, meeting the criteria presented. The accelerated carbonation tests were carried out on the specimen at 28 days of age, and the results showed that the mortar with active hwangtoh had lower carbonation resistance performance than mortar with OPC. The passed charge of each mixture was assessed in accordance with ASTM C 1202 on 28 and 91 aged days. The OPC mixture had "Low" rate and the mortar with active hwangtoh had "Moderate" rate. So it was thought that the mortar with active hwangtoh had appropriate resistance performance for chloride attack.

• 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 Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.405-412
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• 2019

In this study, the physical and chemical properties of mortar are evaluated by micro-analysis, taking into account the substitution rate(20%, 30%, and 40%) of zeolite with porous properties and active hwangtoh. First, the physical and chemical properties of zeolite and active hwangtoh are reviewed to confirm that the specific surface area of those is similar with ordinary portland cement, and the main chemical composition is SiO₂, Al₂O₃, Fe₂O₃, etc.. So, it is thought that they have the properties of pozolan reactive materials. As the results of the strength test considering the amount of substitution based on that of cement, It is confirmed that strength decreases with the increase of the replacement amount of zeolite and active hwangtoh, and the strength of mortar with replacement rate of 20% is higher than OPC mortar. It is confirmed that the amount of porosity is increased due to chemical properties of zeolite and active hwangtoh, and in particular, the size of the pore is greater than 1㎛ in mortar mixed with active hwangtoh.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.197-200
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• 2002

This study is performed to examine the non-destruction properties of the Hwangtoh mortar. The absorption ratio is in the range of $8.25%{\sim}18.16%$, it tend to increase with increase using the stone dust and Hwangtoh. The pulse velocity and dynamic modulus at the curing age 7 and 28days are in the range of $2,290m/s{\sim}4,140m/s,\;2,976m/s{\sim}4,219m/s\;and\;105{\times}10^3kgf/cm^2{\sim}293{\times}10^3kgf/cm^2,\;137{\times}10^3kgf/cm^2{\sim}318{\times}10^3kgf/cm^2$, respectively. They tend to decrease with increase using the stone dust and Hwangtoh.