모르타르의 내구성(耐久性)에 관(關)한 연구(硏究) - (제(第)1보(報)) : 염산(鹽酸)에 의(依)한 부식(腐蝕)에 관(關)하여

고재군 ( Chae Koon Koh ),유한열 ( Han Yeol Ryu ) 한국농공학회 1969 韓國農工學會誌 : 전원과 자원 Vol.11 No.1

This experiment was carried out as one of the basic studies to improve the acid resistance of concrete and it was conducted to investigate some relations among physical properties such as basorption, ratio of water to cement, compressive strength, density and ratio of mix to weight losses of mortar when exposed to 0.1 N solution of hydrochrolic acid. The results obtained from the limited data secured so far in this experiment are summarized as follows: 1. The specimens used in the experiment were made of 5 cubic centimeters of mortar having such various ratios of mix by weight as 1 : 1, 1 : 3, 1 : 5, 1 : 7, 1 : 10. 2. Physical tests included compressive strengths at 7 days, 28 days, 3 months, and 6 month, and 5 hour boiling absorption test. 3. In acid test, every specimen was immersed into 0.1 N solution of hydrochrolic acid. The specimens exposed to the acid solution were weighed to determine the weight losses of the acid-corroded at one week interval for 7 weeks exposure, and the old acid solutions were also changed to fresh one when weighed the weight losses by acid attack at one week interval. 4. The correlative relations were found among physical properties and they are expressed by certain formulas as follows; i) Relation between ratio of mix and absorption Y = 1.036x + 13.53 where Y: absorption(%) X: ratio of mix ii) Relation between ratio of mix and ratio of water-cement Y = 0.204x + 0.214 where Y: ratio of water-cement. X: ratio of mix iii) Relation between ratio of water-cement and absorption Y = 5.01x + 12.53 where Y: absorption(%). X: ratio of water-cement iv) Relation between density and absorption Y = 50.6 - 0.0176X where Y: absorption(%). X: density(㎏/㎥) v) Relation between density and ratio of water cement Y = 7.2183 - 0.0033X where Y: ratio of water-cement . X: density(㎏/㎥) 5. After completing the acid exposure test the specimens were corroded and , the per cent ranges of weight losses varies from a minimum of 20.4 per cent at a 1 : 1 mix to a maximum of 92.0 per cent at a 1:10 mix. 6. The correlative relations of physical properties of mortar to weight losses by acid attak were found and they are also expressed by certain formulas as follows: i) Relation between weight losses and ratio of mix Y = 8.59X + 8.63 where Y: weight losses(%), X: ratio of mix ii) Relation between wieght losses and absorption Y = 0.121x + 12.43 where Y: absorption(%). X: weight losses(%) iii) Relation between weight losses and ratio of w/c Y = 0.0226X + 0.07 where Y: ratio of w/c X: weight losses(%) iv) Relation between weight losses and compressive strength LogY = 3.6097 - 0.05058X + 0.00022X² where Y: compressive strength (㎏/㎤) X: weight losses(%) v) Relation between weight losses and density Y = 2153.1 - 6.62X where Y: density(㎏/㎥) X: weigh losses(%) 7. In order to make better acid resistant mortar, it could be concluded that a 1 : 3 mix or richer mixes, adequate mixing water to minnimize the ratio of water-cement considering the workability, 16 per cent or less absorption by 5 hour boiling water, 1,800 kilogram per cubic meter or denser density by absolute weight base and 200 kilogram per square meter or compressive strength at 20 day, etc are required so as to obtain acid-resistant mortar. In addition to the above, it might be recommonded to select the fine aggregate and to use better equipments such as a mechanical vibrator, a mechanical mixer etc. in concrete manufacturing works.

시멘트기와의 품질개선(品質改善)에 관(關)한 연구(硏究)

고재군 ( Chae Koon Koh ),이창구 ( Chang Koo Lee ) 한국농공학회 1967 韓國農工學會誌 : 전원과 자원 Vol.9 No.1

The experiment was carried out to investigate the qualities of cement mortar roofing tiles which were produced at ordinary roofing tile manufacturing plants and to show some criteria for making better qualities of roofing tiles by experiment results. The results obtained in this experiment are summarized as follows; 1. Two different tiles in their qualities such as special and common have been produced at some roofing tile factories. In order to investigate their qualities they were sampled at random in 12 roofing tile plants located at the city of Suwon. In this experiment, three different ratios of cement to sand by volume such as 1:3,1:6 and 1:12, were also prepared as samples to find out some criteria for the improvement of qualities of roofing tiles. The tests on them were carried out according to the standard testing methods which are specified in the Japanese Industrial Standard (J.I.S). A simplified testing tool for bending was also specially designed and used it for bending test. 2. According to the experimental results on the samples taken from the ordinary different plants, the percentages of the number of tiles satisfied the criteria in J.I.S, were 80 percents for specials and 90 percents for commons on their absorption tests, and about 60 percents for specials and almost zero percent for commons on their bending strength test. It could be said that the results of the absorption rates were much better for both special and common than those of the bending strength. However, as the latter is usually considered to be more important in their qualities, one must pay attention for selecting tiles produced at ordinary roofing tile manufacturing plants. 3. The relation between different ratios of mortar and their optimum ratios of water to cement controlling the absorption rates, can be expressed by the following regression equation; Y=0.1+1/15X where Y: ratio of water to cement X:ratio of mortar 4. The relation between different ratios of mortar at their optimum ratio of water to cement, and bending strengthes are shown in Fig. 7 5. The relation between different ratios of mortar at their optimum ratios of water to cement, and numbers of roofing tiles produced per sack of cement can also expressed by the following regression equation; Y=12.2X where Y: numbers of tiles X: ratio of mortar 9. In accordance with the results obtained in this experiment, it is estimated that the ratios of cement to sand by volume for roofing tiles produced at ordinary roofing plants, would be 1:8 for special ones, and between 1:10 and 1:12 for common ones, respectively, and that their numbers of tiles per sack of cement would also be 95 for the formers, and between 110 and 120 for the latters, respectively. 7. Concerning with the improvement of qualitise of roofing tiles, it is proposed that the least mixing ratio of mortar should be 1:7, the ratio of water to cement being 0.55. In addition, the number of produced per sack of cement should be restricted to less than 85 tiles, and tiles must be cured under water at lease 7 days after removing their molds.

농경지의 토양침식과 수질오염의 예측 및 억제

고재군 ( Chae Koon Koh ) 한국환경농학회 1985 한국환경농학회지 Vol.4 No.2

조수에 의한 콘크리트의 침식방지법에 관한 연구 (II)

고재군 ( Chae Koon Koh ),황경구 ( Kung Koo Hwang ) 한국농공학회 1973 韓國農工學會誌 : 전원과 자원 Vol.15 No.2

This study was carried out to investigate the effects of various mix designs of concrete on the compressive strengths and corrosive rates when the concretes were immersed in sea water of the West Sea, as the part of study related to durated to durability of concrete by action of the sea water. Concrete mix designs used in this study were ordinary Concrete mix, Concrete mixes with different admixtures such as fly ash, pozzolith and vinsol resin, and pozzolan concrete mix. The concrete specimens were made and cured for 7 days and 28 days in the fresh water in accordance with the Korean Standard specification for concrete. Compressive strengths of the specimens were measured after immersing the specimens for one year in fresh water and sea water which were placed indoors. The sea water used in this test was taken from the Bay of Ahsan. Corrosive rate was also tested after immersing the specimens in the same sea water and placed indoors for one year. The results obtained from the tests are summarized as follows; 1. Compressive strength of an ordinary concrete was the lowest of the various mix desings of concrete immersed both in the fresh water and the sea water. Therefore, the uses of pozzolan cement, fly ash, pozoolith and vinsol resin in mix design of concrete had an effect on increasing compressive strength. 2. Pozzolan concrete was the most effective on compressive strength in the fresh water, but it had less effect than concrete with fly ash admixture immersed in the sea water. 3. The use of fly ash admixture in mix design of concrete showed higher strength as the immersing age is longer both in fresh water and sea water than the other concretes besides pozzolan concrete, but the concretewith fly ash admixture had lower strength than pozzolan concrete in the sea water. Therefore, concrete with fly ash admixture might be better than the pozzolan concrete as far as durability of concrete to sea water was concerned. 4. The use of pozzolith admixture in mix design of concrete had less compressive strength than the use of pozzolan cement for fly ash admixture both in fresh water and sea water. However, the concrete with pozzolith admixture was much stronger than one with vinsol resin admixture in fresh water, but somewhat stronger in the sea water. 5. Though the use of vinsol resin admixture was more effective than ordinary concrete on compressive strength both in fresh water and sea water, it was the least compressive strength among the other concretes. 6. Relation between compressive strengths and absorption rates of every kind of concrete besides concrete with fly ash admixture showed a linear regression line and the compressive strength is highee as the absorption rate is lower. Concrete with fly ash admixture had extremely high strength in comparison with corresponding adsorption rates of the other concretes. 7. Corrosive appearance on the surface of concretes was not occured significantly when exposed to the sea water for one year, However, the specimens of concretes besides ordinary concrete were a little heavier than those cured in fresh water for 28 days.

혼화제(混和劑)가 콘크리트의 내산성(耐酸性)과 물리적성질(物理的性質)에 미치는 영향(影響)에 관(關)한 실험적(實驗的) 연구(硏究)

고재군 ( Koh Chae Koon ) 한국농공학회 1971 韓國農工學會誌 : 전원과 자원 Vol.13 No.2

This resarch was attempted as one of studies for improving the quality of concrete, especially for better chemical resistance of concrete to corrosive action of acid. In this study, concrete specimens were made in accordance with the Korean Standards Specifications for concrete, using various admixtures, additives for normal cement, and pozzolan cement. They were tested for strength, absorption and acid-resistance. In mix designs of concrete, different levels of fly ash substituted for cement were varied from 10 to 30 per cent by weight of the normal cement content of the mix. Pozzolith, vinsol resin and fly ash were used as admixtures, of which fly ash was added to the mix in an amount equal to 10 per cent by weight of the cement of the mix, and pozzolan cement whose pozzolan content was amounted to 20 per cent by weight of the mill cement, was used as a different brand of cement. In the tests, compressive strengths of specimens were measured at the following ages; 7-days, 28-days, 3-months and 6-months. Absorption test was made by immersing specimens in the water kept at boiling temperature for 5 hours. In addition, aeid corrosion test was made by exposing 3-months old specimens to the same concentration of 0.1N solutions of hydrochloric acid (HCl), nitric acid (HNO₃), sulfuric acid (H₂SO₄) and phosphoric acid (H₃PO₄) for 8 weeks. Each old acid solution was changed to fresh one at interval of 2 weeks, and their pH values of both old and fresh solutions were measured by using glass electrode pH meter. The results obtained from the data secured in this test are summarized as follows: 1. Fly ash, when substitutes cement in amounts of 10 to 30 per cent by weight of cement, reduces absorption by concrete, and also remarkably reduces the acid-resistance of concrete to acid solutions as fly ash contents are increased. The compressive strength of concrete containing fly ash of 10 per cent by weight of cement decreases a little. However,, by the use of fly ash of 20 per cent by weight of cement as an optimum content of fly ash, compressive strength is distinctively increased at all ages and the early-strength. of concrete is retarded by the use of fly ash by 30 per cent and some 3 months of curing time is required for fly ash concrete to equal or exceed the strength of plain concrete. Accordingly, fly ash could be used for making concrete in an amount equal to 30 per cent by weight of cement, providing that the low-early strength of fly ash concrete is not a handicap. It may be suggested that the early-strength of fly ash concrete would be attained by high temperature curing, the use of high early-strength cement or the use of admixtures that encourage early-strength of the concrete. 2. Strengths of concrete made by adding pozzolith, vinsol resin and fly ash are higher, at all ages, and the difference among their strengths is not significant. Pozzolith, vinsol resin and fly ash as admixtures exhibited promising results in lowering the absorption of concrete and especially vinsol resin and fly ash increase the resistance of concrete to acid solutions. They are the most acid-resistant among all treatments in this experiment. 3. Pozzolan concrete, whose pozzolan content amounted to 20 per cent by weight of mill cement, has the highest strengths at all ages and among all treatments in this experiment. Absorption of pozzolan concrete is lower than plain concrete and fly ash concrete substituted for cement up to 20 per cent by fly ash. However, it is somewhat higher than concrete containing admixtures such as fly ash, vinsol resin,pozzolith or fly ash concrete of 30 per cent replacement by fly ash by weight of the cement. Pozzolan cement decreases remarkably the resistance of concrete to acid solution, contrary to its high strength, so that it may not be feasible when exposed to acid waters or acid soils. 4. As far as improvement of physical property is concerned, it is evident that the use of admixtures, additives and pozzolan cement in experimental mix designs of concrete is definitely effective than the use of normal cement only. In order to make better acid-resistant concrete as well as improvement of physical properties of concrete, it may be recommendable to use pozzolith and fly ash as adimixtures in mix design of concrete. 5. Through physical and acid resistance tests, plain concrete for which no admixtures or additives are used has higher strength, lower absorption and better acid-resistance as the mix is richer. Consequently, it may be said that a rich mix is one of the important factors to make better quality of plain concrete. 6. It is found that corrosive action of acid to concrete is attributed to the concentration of acid solution, pH value and type of acid, and that, in process of acid corrosion, the lower acidity of solution, the wider range of variation of pH value results, and the more acid corrosion of concrete occures due to an intensive chemical reaction. 7. It is known that the action of acid on concrete not only may increase corrosion of concrete but may reduce compressive strength of concrete, may result in increasing absorption by concrete, when concrete is exposed to acid waters.

콘크리트의 내해수성(耐海水性) 시험(試驗)

고재군 ( Chae Koon Koh ),황경구 ( Kyung Koo Hwang ) 한국농공학회 1974 韓國農工學會誌 : 전원과 자원 Vol.16 No.3

This test was attempted to investigate the effects of some mix designs of concreteon the compressive strengths and corrosive rates when exposed to sea water of the West Sea. In this test, concrete mixes consisted of an ordinary concrete, a pozzolan concrete and concretes with different admixtures such as fly ash, pozzolith and vinsol resin. Compressive strengths of the concrete were measured at ages of 1-year and 2-years when exposed to both sea water and fresh water. Corrosive rate was tested at ages of 1-year and 2-years when exposed to sea water only. The results obtained from the test may be summarized as follows: (1) When all of concretes were exposed to fresh water, compressive strength of an ordinary concrete was the lowest at all mixes of concretes, and all of them showed higher strength as the exposing age is longer. It was evidance that the uses of pozsolan cement, fly ash, pozzolith and vinsol resin in mix design of concrete had an effect on increasing compressive strength and that fresh water also had an effect on curing concretes even though at a long-time age. (2) When concretes were exposed sea water, a concrete with fly ash was the highest in compressive strength and its strength was increasing as the exposing age is longer, but the other concretes were decreased at 2-year exposure. It was found that a concrete with fly ash was the most effective on compressive strength of all concrete, but the other concretes were attacked by action of the sea water. (3) The use of vinsol resin admixture was the most resistant to corrosion by sea water, while the use of pozzolith was the most serious at corrosion and the others were corroded to almost same extent. (4) The relationship between corrosions and compressive strengths of concretes was not clearly correlated yet. It was known that the corrosive rate of concretes could not affect to compressive strengths by 2-year exposure of the sea water. (5) Pozzolan concrete was the most effective in compressive strength when exposed to fresh water only, However, the use of a fly ash admixture was available for compressive strength when exposing to both fresh water and sea water. It was also noticed that the use of vinsol resin was not available for strengths of concrete but for resistance to corrosion when exposed to sea water. (6) It was found that the use of pozzolith was so defective in compressive strengths and corrosiive resistance when exposing to sea water that it was only available for fresh water.

강섬유(綱纖維)에 의한 콘크리트의 보강효과(補强效果)

고재군 ( Koh Chae Koon ),이홍기 ( Kim Moon Ki ),이신호 ( Rhee Shin Ho ) 한국농공학회 1985 韓國農工學會誌 : 전원과 자원 Vol.27 No.2

Wasting fiberous residues from the cutting processes of steel materials at an iron-Works were mixed with concrete. The strength and toughness of steel fiber concrete with different steel contents were tested in a laboratory. The test results showed that the steel fiber residues can be used for the reinforcement of concrete. The potential applications of such product include floor constructions for facilities like dairy barns, grain storages, and machinery shops. The test results are as follows. 1. The compressive strengths of steel fiber concrete with one percent steel content by volume were 20 percent greater than that of plain concrete. The treatments also increased the concrete toughness by 96 percent. 2. When applied to tensile forces, the steel fiber concrete showed the increased strengths by 20 percent, and the toughness by 48 percent. 3. The steel content levels greater than or equal to 1.5 percent by volume resulted in the decreases of the compressive and tensile strengths of steel fiber concrete by 10 percent as compared to plain concrete. The concrete toughness increased with the steel contents. 4. The reinforcement effects of steel fiber depend on the quality of fiber material being used. Good steel fiber for concrete reinforcement appears to be uniform in shape and component, fine and long, and round-shaped.

서해 조수에 의한 콘크리트의 부식 방지법에 관한 연구

고재군 ( Chae Koon Koh ) 한국농공학회 1972 韓國農工學會誌 : 전원과 자원 Vol.14 No.2

This study was attempted in order to search for phyosical properties on various mix designs of concrete as ne of studies relating top revention against corrosion by action of sea water in the West Sea. In this study, as concerete mix design, fly ash, pozzolith and vinsolresin were used as admixtures for normal portland cement respectively, and pozzolan cement and normal cement were also used for each plain concrete. Concrete specimens were made and cured in accordance with the Korean Standard Specifications for concrete. In thetest, compressive strengths of the specimens were measured at the following ages; 7-day, 28-days and 3-months. Absorption test was made by immersing the specimens in water kept at boiling temperature for 5 hours. The results obtained from the tests are summarized as follows; 1. The use of fly ash as an admixture in mix design of concrete, has an effect on compressive strength at each age. But it is actually not effective on absorption by concrete, as the result of the fly ash concrete is almost the same at that of ordinary plain concrete. 2. The use of pozzolith as an admixture in mix design of concrete, has an effect on both of compressive strength at each age and absorption rate. The pozzolith is more effective than vinsol resin, relating to improvement for physical prorerties of concrete. 3. The use of vinsol resin as an admixture in mix design of concrete, has also an effect on both of compressive strength at each age and absorption rate. As the above fact, effectiveness of the vinsol resin is some what lower than pozzolith, as far as physical properties of the concrete are concerned. 4. Plain concrete used pozzolan cement only is the most effective on both of strength at each age and absorption rate in this study. The pozzolan cement is characteristic of higher strenth as the age is later. 5. Relationship between compreessive strengths and absorption rates of the concrete is shown by a different regression line dependingon ages. The gradient of the regression line is steeper as the age is later. 6. Throught physical test, it may be expected that the use of pozzolith and vinsol resinas asan admixture respectively will be better resistant than fly ash or ordinary plain concrete and that plain pozzolan concrete will also be the best resistant to action of sea water due to improvement of theirphysical properties.

모르타르의 내구성(耐久性)에 관(關)한 연구(硏究) (제(第)Ⅱ보(報)) 수산화(水酸化)나트륨에 의(依)한 부식(腐蝕)에 관(關)하여

고재군 ( Chae Koon Koh ) 한국농공학회 1969 韓國農工學會誌 : 전원과 자원 Vol.11 No.4

The experiment was carried out as one of the basic studies to improve the alkali-resistance of cement mortars and it was conducted to investigate some propetties of mortars relating to weight losses when exposed to 0.1 N salution of sodium hydroxide. The experiment and the results obtained are summarized as follow; 1. The specimens used in this experiment were made of 5 centi-meter cubes of mortar having such various ratios of mix by weight as 1 : 1, 1 : 3, 1 : 5, 1 : 7 and 1 : 10. 2. Physical tests included compressive strengths at 7 days, 28 days, 3 months, and 6 month, and 5 hour boiling absorption test. 3. In alkali test, every specimen was immersed into 0.1 N solutions of sodium hydroxide. The specimens exposed to the alkali solution were weighed to determine the weight losses of the alkail-corroded at one week interval for 7 week's exposure and the old alkali solutions were also changed to fresh solutions when weighed the weight losses by alkali attack at one week interval. 4. According to the alkail test after 7 week's exposure, no weight losses were observed on ratios of mix 1:1 and 1:3 and slight weight losses occurred on ratios of mix 1:5 and 1:7, but relatively large amount of weight losses were showed by 36.6 per-cent on ratios of mix 1:10. It was also found that the weight losses of the alkali-corroded were extremely lower than those of the acid-corroded at the some concentrations as 0.1 N of solutions. 5. In order to make better quality of alkali-resistant mortar it might recomend that a 1:7 mix or richemixes, use of small amount of mixing water for watertight, 20 per cent or less absorption by 5 hour boiling 1,600 kirogram per cubic meters or denser densities by absolute dry base are available for physical properties of mortar. It could conclude acid-resistant mortars were so high alkali-resistant, that it is expected to make and improve the acid-resistant mortars for getting rid of damages by alkali attack.

혼화제(混和濟)가 콘크리트의 내산성(耐酸性)과 물리적성질(物理的性質)에 미치는 영향(影響)에 관(關)한 실험적(實驗的) 연구(硏究) (II)

고재군 ( Chae Koon Koh ) 한국농공학회 1971 韓國農工學會誌 : 전원과 자원 Vol.13 No.3