방화석고보드 두께 및 접착방식 변화에 따른 고강도 콘크리트의 폭렬특성

한천구,배장춘,장기현 청주대학교 산업과학연구소 2008 産業科學硏究 Vol.26 No.1

This study investigates fire resistance properties of high strength concrete designed with various thickness and adhesive methods of fireproof gypsum board. Test results showed that compressive strength of control concrete indicated 89.9MPa, which is high strength rage. For the fire test results, uncovering top section of specimens caused severe spalling occurrence in all sides, exposing mostly re-bars. Moreover, some specimens even exposed main bars of concrete. However, covering top section of specimens protected from fire and resulted in secured high strength concrete. The maximum temperature of main bars in 19BN-W indicated 1017℃, in 19MB-W was 1061℃, in 19MN-W was 1036℃, in 25MB-W was 583℃ and in 19MN-T was 271℃ respectively. 19MB-W had the highest value of weight loss ratio, indicating 54%, while 25MB-W showed 43% of weight loss ratio, 19BN-W was around 40%, 19MN-W was around 27% and 19MN-T was around 7%.

조강성 혼화제 종류에 따른 콘크리트의 물리적 특성

한천구,한민철,노상균 청주대학교 산업과학연구소 2009 産業科學硏究 Vol.26 No.2

The purpose of this study is to compare and analyze the physical properties of concrete in connection with the recent trends to reduce construction periods, in order to increase early-strength of the concrete where the various kinds of liquified early strength concrete agent are used. As for the experiment plan in two levels such as the W/C 30, 50 %, which the standard air entraining water reducing agent(The following P) was intermixed as the plain, the early-strength agent of MAS serial(The following A), the AE reducing agent of early-strength type of the polycarbonic acid serial(The following B) and the naphthalene+lignin serial(The following C) were selected to change them into 4 levels, so that total 8 levels might be included in the experiment. According to the results, the setting time accelerated as the B was fastest and followed by A and C. And as for the compressive strength, the strength development of A recorded 115 %, B recorded 95% and C recorded 80 % of the plain mixture respectively when they were compared with the plain mixture at one day of age, but in the case of 3 days of age, a recorded 103 %, B recorded 104 % and C recorded 110 % of the plain mixture respectively. On the other hand, when A was added the air content increased by 2 %, so it is judged that the compressive strength of A would more than by 10% in consideration of the fact that the compressive strength fell off by 4~6 % when the air content increased by 1 %.

유기질 섬유 보강재를 사용한 시멘트 모르터의 특성

한천구,이건철,신현섭 청주대학교 산업과학연구소 2006 産業科學硏究 Vol.23 No.2

This study reported the result of experiments as to engineering properties of cement mortar with organic fiber types, such as cellulose(CEL), nylon(NY), polypropylene(PP) and polyvinyl Alcohol (PVA) and their contents. For the properties of fresh concrete, slump flow of almost all concrete, adding fiber less than 0.1% by volume, increased, but the flow of concrete adding more than 0.1% decreased, except for PVA fiber. Furthermore, air content increased as NY and PP fiber content increase, and PVA fiber content decrease. For the properties of hardened concrete, compressive strength at early age had no significant effect, but the strength value of concrete adding 0.1%, at 28 days, increased. This test results demonstrated that proper amounts of fiber have favorable strength value. Tensile strength of concrete adding 0.1%~0.15% also exhibited improved value, especially adding NY fiber, was pretty remarkable, even if physical properties and improved air content are considered. For the dry shrinkage properties, increase of CEL and PP fiber content resulted in first increase and decrease. However, increase of dry shrinkage was proportional to the increase of NY and PVA fiber content.

3종류 잔골재를 조합 사용한 시멘트 모르터의 특성

한천구,윤기원,박용규 청주대학교 산업과학연구소 2005 産業科學硏究 Vol.23 No.1

This paper investigated the engineering properties of cement mortar mixed with more than two kinds of fine aggregate. For fresh mortar properties, unit volume weight is constant regardless of mixing content and type of fine aggregate. An increase in contents of natural fine aggregate and crushed fine aggregate resulted in an increase in flow, whereas an increase in recycled fine aggregate contents reduced flow. Gap between maximum flow in N_(3)C_(0)R_(0) and minimum flow in N_(0)C_(0)R_(3) exhibited about 12%. Compressive strength at 28 days ranged from 32 to 36 MPa in order for crushed fine aggregate, natural fine aggregate and crushed fine aggregate showed compressive strength comparable to that of crushed fine aggregate. An increase of fraction of recycled fine aggregate in mixed fine aggregate resulted in a decrease in compressive strength. For drying shrinkage, N_(0)C_(0)R_(3) had the largest drying shrinkage among various mixture type. The combination of large contents of recycled fine aggregate and small contents of natural and crushed fine aggregate had a large amount of drying shrinkage.

석회암 성분의 부순잔골재를 사용한 모르터의 역학적 특성

한천구 청주대학교 산업과학연구소 2006 産業科學硏究 Vol.24 No.1

This study investigates engineering properties of mortar using limestone-crushed-aggregate (LS). Test resulted show, that increase of incorporating ratio of Ls had better fluidity than other specimens. This is due to the particle shape and continuous grade distribution of Ls. In addition, mortar incorporating more Ls exhibited lower air content, by the well-filling effects of the aggregate. Among specimens, It was found that Ls affected to the setting time of the mortar, resulting from acceleration of the initial and final setting time. For the properties of strength, specimens incorporating higher ratio of Ls had favorable strength, such as higher compressive, tensile and flexural values, Drying shrinkage length, change ratio of the specimens exhibited that Ls was the lowest and it reduced the shrinkage, as the incorporating ratio of Ls increased, due to the improved strength.

주택성능등급제에 따른 레미콘 산업의 대응방안

한천구,이건철,오상백,박용규 청주대학교 산업과학연구소 2006 産業科學硏究 Vol.24 No.1

This study investigates the regulations on concrete grade evaluation, in response to operation of housing performance grade system(HGS). It also studies countermeasure- of ready mixed concrete industry. Because the HGS provide people who have to invest in housing once during their whole life, with objective information of housing performance, housing consumers would easily understand and purchase better house. In addition housing construction companies will try to supply the high quality housing, in response to people's various housing performance needs. It is expected that housing quality improvement and housing components technology development will be nationally activated, due to the competition on housing quality between the construction companies. After this, HGS is now on design process but will be on construction process connecting specification, which is perfoiniance based design and on the process after completion. It is assumed that those regulations will be possibly continued to develope for housing performance guarantee system.

혼화재 다량 치환 콘크리트의 품질향상에 관한 기초적 연구

한천구 청주대학교 2009 産業科學硏究 Vol.26 No.2

In this study, it was designed to devise a quality improvement method to make up for the problems that are occurring when the mineral admixtures like FA(Fly-Ash) and BS(Blast Furnace Slag) are used in great quantity, by approaching the methods from chemical and physical basis. And the summarized contents are as follows. As for the concrete properties before setting, in the case of fluidity, the EAE(Early AE agent) appeared to have highest value but the FCE(Fine Particle Cement) appeared to have the lowest value among the admixtures. And other mixtures did not appeared to be much different from OPC, and in the case of air, it was identified that besides the B-P mixture, all other mixtures could not reach the target air content. As for the setting time, the mixture of NAO(NaOH) and FCE brought about the relatively satisfactory results, which are the alkali activators as the quality improvement admixtures. As for the properties of hardened concrete, the semi-adiabatic temperature history appeared to be high when it was NAO at the BS and in the case of quality improvement admixtures, but in the other cases it appeared to be similar to the plain mixtures or a little lower than the plain mixture. In the case of compressive strength, all kinds of quality improvement admixtures appeared to be lower than the plain mixture, but in the case of BS, the NAO was satisfactory at the third day of the early stage of age. And in the case of mixture where the large quantity of FA and BS were used, the FCE appeared to be most excellent at the 91st day of aging.

시멘트 킬른 더스트를 사용한 콘크리트의 역학적 특성에 관한 연구

전충근,차천수,차완호,손성운,한천구 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)

This paper is intended to investigate the properties of fresh and hardened concrete, in which cement and fine aggregate are replaced with cement kiln dust(CKD), for effective using method of CKD, a by-product produced in the process of making cement. According to the results, as the replacing ratio of CKD increases, slump and air content of concrete decreases remarkably due to an increase of viscosity and filling of the pores respectively. As the properties of setting, setting time are shortened with an increase of the replacing ratio of CKD. Compressive strength increases due to the filling effect of the pores in comparison with plain concrete, and compressive strength ratio is high at early age.

콘크리트의 블리딩에 미치는 혼화재의 영향

황인성,文學龍,金光華,한천구 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.1(구조계)

This study is to investigate the influence of contents of mineral admixture on bleeding of concrete. According to the results, as W/B increases, bleeding occurs rapidly at early age regardless of replacement of mineral admixture, and when slump and air content are kept equal, the amount of bleeding decreases proportionately with an increase of replacing ratio of fly ash and blast furnace slag powder. Bleeding speed is highest at 60 minutes after placing concrete, and grow slower after 180 minutes. Bleeding speed also grows high with an increase of W/B, and is lower in the case of fly ash than in the case of blast furnace slag powder.

폴리프로필렌섬유의 형상비 및 길이조합 변화에 따른 고강도 콘크리트의 폭렬특성

송용원,허영선,한천구 청주대학교 산업과학연구소 2007 産業科學硏究 Vol.24 No.2

This study investigates spilling resistance of high strength concrete, 60∼80MPa class, designed with the various adding and aspect ratios of polypropylene(PP) fiber. Test showed that increase of PP fiber content and aspect ratio decreased the fluidity of fresh concrete. Especially, the slump flow significantly decreased in the specimens containing certain fibers being 475 and 750 of aspect ratios. Compressive strength of specimtls containing fibers, 300 and 475, exhibited 5 percent higher thin other specimens. Specimens containing combination of diverse fiber lengths declined the value about 10-25% than that of control concrete. In addition, specimens containing more thin 0.lvol% of PP fiber, T00, hid favorable spilling resistance, while specimtls containing PPsxl(3mm+19mm) and PPmxl(6mm+19mm) was O.1vol% and specimens containing PPsl(3mm+12mm) and PPml(6mm+12mm) was 0.15vol%. Therefore the specimen, containing 0.1vol% of PP fiber, T00, exhibited the most effective fluidity, strength is well is the side of economy.