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시멘트 제조사 및 W/C 변화에 따른 콘크리트의 초기 강도발현 특성
金光華,裵正烈,김규도,이승훈,한천구 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)
This study is to investigate the influence of cement manufacturing company and W/C on the properties of fresh concrete, strength of hardened concrete and rebound value of P type Schmidt hammer. According to the result, setting time of concrete is shortened with and increase of W/C, and when cement made in A and B corporation is used in concrete, the final setting time is measured at about 10 hours and 13 hours. Compressive strength increases with elapse of time and decrease of W/C, and concrete using cement made in A corporation shows higher compressive strength and rebound value until 24 hours, but from 3rd day, the contrary tendency is shown. As for the properties of early strength, the strength develop fast with decrease of W/C, and the time when compressive strength of 5MPa is gained and the form can be removed, is about 15, 18, 21 hours and 20, 22, 27 hours at the W/C 40, 45, 50% in concrete using cement made in A and B Co. respectively. The correlativity between compressive strength and the rebound value, which a coefficient of correlation is over 0.97, is very favorable. Therefore this method is effective to estimate the strength of removing the form.
金光華,김종,한민철,정평유,한천구 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1(구조계)
The objective of this paper is to investigate the physical and mechanical properties of concrete incorporating shrinkage reducing admixture(SRA) and mineral admixture(MA) such as fly ash and blast furnace slag powder. According to results, for fresh concrete properties, increase of SRA content leaded to reduce the fluidity and air content sharply. For setting time, use of SRA caused concrete to accelerate setting time, and compared with plain concrete it retarded by incorporating MA. Compressive strength decreased with an increase in SRA content, and when incorporating MA, compared with plain concrete, it shows lower compressive strength in early age but similar or increase by the elapse of age due to the pozzolanic and latent hydration reaction. For drying shrinkage, concrete shows decline tendency with an increase in SRA content due to the relaxation effect at the capillary tension in concrete by SRA. In the scope of this paper, it is found that the use of SRA with 1.0% has optimum effects on the various properties of concrete, and the combinations of SRA and fly ash will ensure the stability for drying shrinkage.
회수수 안정화제를 사용한 콘크리트의 공학적 특성에 관한 연구
김기정,金光華,이문환,이세현,한천구 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2
In this study is investigated the engineering properties of concrete using stabilizing agent of recycling water in order to suggest a practical use of recycling water. According to the results. as stabilizing agent is added. fluidity and air content varies slightly with W/C, but does not make a big difference. Bleeding is reduced by adding stabilizing agent, and so it decreases by about 40% at the adding ratio of 0.15%. When stabilizing agent is not added, compressive strength decreases in comparison with plain concrete, but increases by adding stabilizing agent, so it is largest at adding ratio of 0.30%(W/C 30%) and 0.15%(W/C 40, 50%). Length change by drying shrinkage is larger than plain concrete in the case of no adding of stabilizing agent, but decreases by the use of stabilizing agent. Therefore, it is thought that when stabilizing agent is added to recycling water, quality deterioration of concrete is prevented, moreover, quality of concrete can be improved.
트리에탄올아민의 혼입률 변화에 따른 콘크리트의 초기 강도발현 특성
황인성,金光華,김규동,이승훈,한천구 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)
In this study, the influence of TEA on early strength development of concrete is discussed in order to reduce a construction period in RC structure by early removal of forms. According to the results, as for the properties of fresh concrete, fluidity of concrete shows no difference, and air content increases with an increase of the mixing ratio of TEA. Setting time is shortened upto mixing ratio of 0.025%, but is retarded above the mixing ratio of 0.025%. The time when compressive strength gains 5MPa is fast in about 2 hours in the case of the mixing ratio of 0.05%, but it is retarded above the mixing ratio of 0.05%. The relativity between compressive strength and the rebound value of P-type Schmidt hammer is also favorable at early age, and compressive strength of 5MPa, which the side forms can be removed, is estimated at the rebound value of 23.
수축저감제 혼입률 변화에 따른 콘크리트의 공학적 특성에 관한 연구
한민철,金光華,정규문,정평유,윤성노,한천구 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2
In this paper, tests are carried out using concrete incorporating shrinkage reducing agent(SR) in order to investigate the engineering properties of concrete. The contents of SR and W/C are varied. According to test results, as for fresh concrete, as SR content increases, slump and air content shows decline tendency, and setting time is accelerated with increase of SR content and decrease of W/C. As for compressive strength, as SR contents increases compressive strength shows to be decreased. As for the effect of SR on drying shrinkage, it shows to be reduced with increase of SR content. This is due to the reduced surface tensile strength of water and tensile strength of capillary pore in concrete.
김기훈,金虎林,金光華,윤기원,한천구 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1(구조계)
Crushed sand is made by crushing the rock artificially. With the wide shortage of natural fine aggregates at all regions in Korea. crushed sand has been increasingly consumed as a alternative aggreagtes of natural sand. But there is insufficient information related to the actual situation on the produce. quality and manufacturing company of crushed sand. In this paper. survey is performed in order to know actual consumption situation of crushed sand through ready mixed concrete company in domestic. The remicon companies using crushed sand were estimated with 55%. According to the using method of crushed sand. most remicon company used fine aggregates by mixing natural sand and crushed sand. It is found that natural sand is replaced by crushed sand by about 20~50%. For quality problems in using crushed sand. grain shape. grade and fine particles shall be improved to meet the quality requirement of remicon and wide application. Therefore. it is found that quality improvement of crushed sand is required.
Guang-Hua Xie,Sun Eun Choi,Myung-Jae Mun,Jae-Hun Jeong,Kwang-Hyun Park 한국자원식물학회 2018 한국자원식물학회지 Vol.31 No.3
Hepatic ischemia-reperfusion injury (HIRI) is linked with high mortality rate. Several agents have been developed so far to reduce the risk of HIRI. In this study, we investigated the effects of combined treatment of Ginko biloba leaves extract and vitamin C (GLEVC) on hepatic ischemia-reperfusion injury. To explore the protective effects of GLEVC on HIRI rats model were tested. After the development of HIRI by using clamping method rats were then randomly divided into four groups. Different doses of GLEVC were administered in HIRI rat model. The level of ALT, AST, SOD and MDA content in serum were detected in HIRI groups. Moreover, the activity of SOD, content of MDA, and GSH in hepatic tissue were also examined. Bcl-2 and Bax protein expression were detected by immunohistochemical staining method. Compared with sham group, GLEVC has the protective effect on the HIRI-induced model. Level of ALT, AST, and MDA in blood were significantly lower in GLEVC group compared with HIRI-induced group. Moreover, SOD activity and GSH were increased in GLEVC group whereas MDA content was reduced by GLEVC treatment. Furthermore, HIRI-induced Bax protein was reduced upon GLEVC treatment, whereas Bcl-2 protein expression was enhanced. These results demonstrate that GLEVC treatment may provide potential ameliorative therapy by reducing damaged signaling mechanism in hepatic ischemia/reperfusion injury model.
Guang-Hua Xie,정재훈,최선은,정승일,박광현 한국자원식물학회 2017 한국자원식물학회지 Vol.30 No.6
Hepatic ischemia-reperfusion injury (HIRI) is linked with high mortality rate. Several agents have been developed so far to reduce the risk of HIRI. In this study, we investigated the effects of Acanthopanax senticosus extract (AS) on hepatic ischemia-reperfusion. To explore the protective effects of A. senticosus extract injection (ASI) on hepatic ischemia-reperfusion injury rats animal model were used. After the development of HIRI by using clamping method rats were then randomly divided into five groups. Different doses of AS were administered in HIRI rat model. The level of ALT, AST, and MDA content in serum were detected in sham and HIRI groups. The activity of SOD, MPO and Ca2+-ATPase, content of MDA, and cAMP in hepatic tissue were also measured. Expression of Bcl-2 and Bax protein were detected by immunohistochemical staining method. Compared with sham group, ASI has the protective effect on the HIRI model in rats. Blood levels of ALT, AST, SOD, MPO, and MDA were significantly lower in ASI group compared with HIRI. Indeed SOD and Ca2+-ATPase activities, MDA content, and cAMP level were improved in ASI group. Furthermore, Bcl-2 and Bax protein were improved in ASI group compared with only HIRI group. These results suggest that AS may provide potential ameliorative therapy by inhibiting the damage signaling mechanism in hepatic ischemia/reperfusion injury model.