• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.73-76
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• 1999

In recent, concrete material like specific cement and additives having many functions hsa been developed. In road pavement, ultra high early strength cement or organic material are used to open the road early, but there are many restrictions like workable time and special equipment. We aim to developed specific concrete which 1 day strength is over 300kgf/$\textrm{cm}^2$ to open the road within one day and workable time is maintained over 1 hour that can make the concrete ready mixed concrete. In this study, we are convinced if the ratio of hauyne clinker or its additive is increased early strength property is progressed and if the ratio of non hydrous gypsum is increased longtime strength is progressed. The concrete strength is 290-310 kgf/$\textrm{cm}^2$ at 1 day, 570-640 kgf/$\textrm{cm}^2$ at 28 day and the workable time is maintained over 30 minutes. As the results of this experiments We find out the possibility to developed the 1 day usable ready mixed concrete with high early strength.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.507-512
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• 2002

In road pavements, it is known that cement concrete pavement has superior durability. But in repairing pavement, cement concrete pavement is not usually applied because of the length of time while the road is interrupted when using Ordinary and Rapid-hardening Portland Cement. And Super High Early Strength Cement and Ultra Super High Early Strength Cement are not favorable for ready mixed concrete because of rapid setting time, high slump loss and other restrictions. We developed special cement developing 1 day strength of over 30.0N/$mm^2$ to open the road within 1 day and workable time is maintained over 1 hour so that it can be used as ready mixed concrete. We performed experimental overlay construction with concrete and evaluated the properties of the fresh and hardened concrete. The flexural strength was over 5.0N/$mm^2$ and the compressive strength was over 30N/$mm^2$ at 1 day. So it is thought that the road can be open to traffic within 1 day after placement.

• 한국농공학회지
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• 제17권1호
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• pp.3685-3701
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• 1975

This study was conducted to investigate the strength of soil cements for varied molding water content and cement content(3,6,9,12%) in four cementstabilized soils(KY: sand, MH: sad, SS: sandy loam, JJ: loam). The eoperimental results obtainedfrom unconfined compressive strength tests are asfollows: 1. The optimum moisture content increased in accordance with the increase of the cement while maximum dry density didn't change uniformly. 2. The moisture content for maximum strength was higher than the optimum moisture content in the higher cement content. Moisture-density curves showed a dull peak in the higher cement contents, on the other hand, a sharp peak in the lower cement contents. 3. In molding the specimen with the approximate optimum moisture content, the maximum strength showed at the wet side of the optimum moisture content. 4. SS and JJ maybe used as cement-stabilized base of road to require 300PSI of compressive strength cured seven days, but MH and KY may be not adequate. 5. In soil cement, the better the grain size distribution was, the stronger the compressive strength was itn general. 6. The relation between 28-day strengh and 7-day strength in the cementstabilized four soils may be expressed as follows: q28=1.55q7+1.5 in which q28:28-day strength. q7:7-day strength.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.295-300
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• 2001

In road pavements, it is known that cement concrete pavement has superior durability, safety in compared with asphalt concrete pavement. But in reparing pavement cement concrete pavement is not usually applied because of the length of time while the road is interrupted when using Ordinary and Rapid-hardening Portland Cement. And Super High Early Strength Cement and Ultra Super High Early Strength Cement are not favorable for ready mixied concrete because of rapid setting time, high slump loss and other restrictions. We aim to develope specific cement and concrete developing 1 day strength of over 300 kg/$cm^{2}$ to open the road within one day and workable time is maintained over 1 hour that can be used as ready mixed concrete. In this study, we Produced cement using rapid-hardening cement, Hauyne clinker, anhydride gypsum and accelerator and studied on its properties. The concrete strength was over 300 kg/$cm^{2}$ at 1 day and 550 kg/$cm^{2}$ at 28 day and workable time was maintained for over 1 hour.

• 콘크리트학회논문집
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• 제16권1호
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• pp.102-110
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• 2004

최근 시멘트 및 골재 등 원재료 값의 상승 및 세계적인 유가 급등으로 인한 운송비의 증가로 레미콘 제조원가는 상승하고있다. 그러나 레미콘 제조업체들 간의 과당경쟁으로 인해 레미콘의 납품 단가는 오히려 낮아지고 있는 실정이다. 이를 극복하기 위한 일환으로 레미콘 제조업체들은 레미콘의 제조원가를 최소한으로 줄이고자 하는 노력 중 하나로 고로슬래그미분말 및 플라이애쉬를 혼화재로 사용하는 업체가 증가하고 있다. 그러나 이러한 광물질 혼화재를 사용한 콘크리트의 품질관리에 대한 연구는 미흡한 실정이다. 따라서, 본 연구에서는 고로슬래그미분말 혼합 콘크리트의 28일 압축강도를 조기에 예측하기 위해 열수양생법 및 표준양생에 의한 7일 압축강도를 이용하였다. 고로슬래그미분말 혼합률 별로 선형회귀분석을 실시하여 추정식을 제시하였고 90%의 신뢰구간을 나타내었다. 또한 실험의 신뢰성을 높이기 위해 모든 배합은 3회 반복하였고, 배합순서는 랜덤추출법을 사용하였다. 이러한 실험결과 열수양생법에 의한 1일 촉진강도로서 고로슬래그미분말 혼합 콘크리트의 재령 28일 압축강도를 예측할 수 있는 추정식의 신뢰성을 확인하는 성과를 얻었다.

• Computers and Concrete
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• 제5권1호
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• pp.21-36
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• 2008

Steel fiber reinforced concrete is increasingly used day by day in various structural applications. An extensive experimentation was carried out with w/cm ratio ranging from 0.25 to 0.40, and fiber content ranging from zero to1.5 percent by volume with an aspect ratio of 80 and silica fume replacement at 5%, 10% and 15%. The influence of steel fiber content in terms of fiber reinforcing index on the compressive strength of high-performance fiber reinforced concrete (HPFRC) with strength ranging from 45 85 MPa is presented. Based on the test results, equations are proposed using statistical methods to predict 28-day strength of HPFRC effecting the fiber addition in terms of fiber reinforcing index. A strength model proposed by modifying the mix design procedure, can utilize the optimum water content and efficiency factor of pozzolan. To examine the validity of the proposed strength model, the experimental results were compared with the values predicted by the model and the absolute variation obtained was within 5 percent.

• Child Health Nursing Research
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• 제4권1호
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• pp.17-30
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• 1998

In order to investigate the effects of a decreased activity on skinfold thickness, circumference and muscle strength of the extremities during the recovery period following heart surgery, skinfold thickness, circumference and muscle strength of the extremities were measured on days 0, 3, 6, and 9 following the surgery, and compared with those on the arrival day of intensive care unit. Skinfold thickness was measured using a skinfold caliper(Saehan Cor., Korea), circumference of the limbs were measured with a tape measure, upper extremity strength was determined using the Takei grip dynamometer and lower extremity strength was measured by pressing the flatfoot on an electronic digital health meter while tying on a bed. Results from this study were thus : 1. Skinfold thickness of triceps, quadriceps and gastrocnemius muscle on days 3, 6, 9 following the heart surgery was not significantly different from that of on the day of operation. 2. Circumference of midupperarm and midthigh on days 3, 6, 9 following the heart surgery was not significantly different from that of on the day of operation. Circumference of midcalf on days 3, 6 following the heart surgery was not significantly different from that of on the day of operation, while that of midcalf on day 9 following the surgery decreased significantly compared with that of on the day of operation. 3. Muscle strength of the upper extremity was not significantly different from that of on the day of operation, while that of the lower extremity on day 9 following the surgery decreased significantly compared with that of on the day of operation. From these results, it may be concluded that circumference and muscle strength of lower extremity can be decreased due to the postoperative inactivity following heart surgery in congenital heart disease children.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.233-238
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• 2001

In road Pavements, it is known that cement concrete pavement has superior durability, safety compared with asphalt pavement. But in repairing pavement, cement concrete pavement is not usually applied because of the length of time while the road is interrupted when using Ordinary and Rapid-hardening Portland Cement. And Super High Early Strength Cement and Ultra Super High Early Strength Cement are not favorable for ready mixed concrete because of rapid setting time, high slump loss and other restrictions. We aim to develope special cement and concrete developing 1 day strength of over 300 kg/$\textrm{cm}^2$ to open the road within one day and workable time is maintained over 1 hour that can be used as ready mixed concrete. In this study, we produced cement using rapid-hardening cement, Hauyne clinker, anhydride gypsum and accelerator and studied on its properties. The comperssive strength was over 400 kg/$\textrm{cm}^2$ and tensile at 1 day and workable time was maintained for over 1 hour.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.607-612
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• 2002

In road pavements, it is known that cement concrete pavement has superior durability, safety compared. But in repairing pavement, cement concrete pavement is not usually applied because of the length of time while the road is interrupted when using Ordinary and Rapid-hardening Portland Cement. And Super High Early Strength Cement and Ultra Super High Early Strength Cement are not favorable for ready mixed concrete because of rapid setting time, high slump loss and other restrictions. We developed special cement developing 1 day strength of over 30.0N/mm$^2$ to open the road within 1 day and workable time is maintained over 1 hour so that it can be used as ready mixed concrete. We performed experimental overlay construction with the cement and evaluated the mechanical property and the durability. At curing temperature of 8-l8$^{\circ}C$,the flexural strength was 6.4N/mm$^2$at 1 day, so that the road can be open to traffic within 1 day. In durability test, the hardened concrete showed higher durability than Portland cement concrete.

• 대한간호학회지
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• 제24권1호
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• pp.115-128
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• 1994

The purpose of this study was to observe the change of circumference, volume and strength of normal and operated lower extremities on 3rd, 7th, 10th, and 14th days of postoperation following THRA compared with their condition on preoperation day. Subjects consisted of 13 male and 7 female Patients operated with THRA between the age of 20 and 69 years with a mean age of 38.55(SD=15.1). Circumference of upper and lower leg was measured by tape, leg volume was determined according to formula (Moor & Thornton, 1987) with measurement of 8 circumferences of leg. Leg strength was measured by pressing the center of digital health meter in supine position. The results can be summarized as follows : 1. Circumference of operated thigh decreased significantly at 14 following THRA compared with preoperative value, while that of normal thigh decreased significantly at day 3, 7, 10 and 14 after THRA compared with preoperative value. 2. Circumference of midcalf in both operated and normal limb decreased significantly at day 3, 7, 10 and 14 following THRA compared with preoperative value. 3. Leg volume of operated lower limb decreased significantly at 10, 14 following THRA compared with preoperative value, while that of normal limb decreased significantly at day 7 & 10 after THRA compared with preoperative value.4. Leg strength of operated limb decreased significantly at day 3, 7, 10, 14 following THRA compared with preoperative value. No significant difference of normal leg strength was shown following THRA. 5. Circumference of midcalf differed significantly at day 14 after THRA between normal and operated extremity. From these results, it can be suggested that a decreased activity after THRA caused muscle atrophies in normal and operated extremity.