• Journal of the Korea institute for structural maintenance and inspection
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• 제18권5호
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• pp.34-40
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• 2014

High-performance fiber-reinforced cement composite (HPFRCC) shows very high autogenous shrinkage, because it contains a low water-to-binder ratio (W/B) of 0.2 and high fineness admixture without coarse aggregate. Thus, it needs a method to decrease the cracking potential. Accordingly, in this study, to effectively reduce the shrinkage of HPFRCC, a total of five different ratios of SRA (1% and 2%), EA (5% and 7.5%), and a combination of SRA and EA (1% and 7.5%) were considered. According to the test results of ring-test, a combination of SRA and EA (1% and 7.5%) showed best performance regarding restrained shrinkage behavior without significant deterioration of compressive and tensile strengths. This was also verified by performing modified drying shrinkage crack test.

• Journal of the Korea Concrete Institute
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• 제14권1호
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• pp.76-82
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• 2002

The rapid-set cement concrete causes high hydration temperature and nay result in a high drying shrinkage and shrinkage-induced cracking. This problem may be fixed by incorporating polypropylene fibers in rapid-set cement concrete, because of increased toughness, resistance to impact, corrosion, fatigue, and durability. A series of concrete drving shrinkage tests was peformed in order to investigate the shrinkage properties of polypropylene fiber reinforced concrete with experimental variables such as concrete types, fiber reinforcement, W/C ratio, with and without restraint. Uni-axially restrained bar specimens were used for the restrained shrinkage tests. The results were as follows; The dry shrinkage of rapid-set cement concrete was much lessor than that oi OPC, probably because of smaller weight reduction rate by early hydration and strength development. The constraint and bridging effects caused by polypropylene fibers were great for the rapid-setting cement concrete when compared with that of plain concrete, and this resulted In increased resistance against tensile stress and cracking.

• 한국도로학회:학술대회논문집
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• 한국도로학회 2004년도 학술발표회 논문집
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• pp.137-142
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• 2004

• Computers and Concrete
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• 제4권6호
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• pp.437-456
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• 2007

The shrinkage of large reinforced concrete floors often gives rise to cracking problems. To identify the problematic areas, shrinkage movement analysis is often carried out by finite element method with proper creep and shrinkage models using step-by-step time integration. However as the full stress history prior to the time interval considered is necessary, with the increase in the number of time intervals used, the amount of computations increases dramatically. Therefore a new method using the shrinkage-adjusted elasticity modulus (SAEM) is introduced so that analysis can be carried out using one single step. Examples are presented to demonstrate its usefulness.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.95-100
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• 2003

The shrinkage of high strength/high performance concrete is very important property for the good working of a structure since it very often generates early age cracking due to thermal and autogenous shrinkage. Autogenous shrinkage occurs as a result of internal moisture depletion due to hydration and temperature-induced effects. The level of autogenous shrinkage occurring due to hydration also depends on temperature history at very early age. It is necessary that effect of temperature on autogenous shrinkage is investigated since the stress generated due to autogenous shrinkage is quantified. In this study, Effect of hydration heat evolution on autogenous shrinkage of high strength concretes with W/C=25-40% was investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.17-20
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• 2005

In this study, the properties of autogenous shrinkage stress and dry shrinkage stress for high strength concrete using Type I and Type IV cement were discussed. According to experimental results, autogenous shrinkage stress of SN30(the high strength concrete using type I cement) shows values higher than SL30(the high strength concrete using type IVcement). It is observed that the total shrinkage stress of SN30 is higher than that of SL30, because the ratio of autogenous shrinkage stress of the total shrinkage stress is relatively large. Therefore, SL30 is more effective to control or minimize the cracking of the high strength concrete, compared with SN30.

• Structural Monitoring and Maintenance
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• 제10권2호
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• pp.155-174
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• 2023

High performance concrete (HPC) has been extensively used in thin overlay for repair purpose due to its excellent strength and durability. This paper presents an experiment, where the sensor-instrumented HPC overlays have been followed by dynamic strain and moisture content monitoring for 1 year, under normal traffic. The vibrating wire and soil moisture sensors were embedded in overlay before construction. Four given HPC mixes (2 original mixes and their shrinkage-modified mixes) were used for overlays to contrast the strain and moisture results. A calibration method to accurately measure the moisture content for a given concrete mixture using soil moisture sensor was established. The monitoring results indicated that the modified mixes performed much better than the original mixes in shrinkage cracking control. Weather condition and concrete maturity at early age greatly affected the strain in concrete. The strain in HPC overlay was primarily in longitudinal direction, leading to transverse cracks. Additionally, the most moisture loss in concrete occurred at early age. Its rate was very dependent on weather. After one year, cracking survey was carried out by vision to verify the strain direction and no cracks observed in shrinkage modified mixes.

• Steel and Composite Structures
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• 제7권3호
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• pp.219-240
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• 2007

An analytical-numerical procedure has been presented in this paper to take into account the nonlinear effects of concrete cracking and time-dependent effects of creep and shrinkage in the concrete portion of the continuous composite beams under service load. The procedure is analytical at the element level and numerical at the structural level. The cracked span length beam element consisting of uncracked zone in middle and cracked zones near the ends has been proposed to reduce the computational effort. The progressive nature of cracking of concrete has been taken into account by division of the time into a number of time intervals. Closed form expressions for stiffness matrix, load vector, crack lengths and mid-span deflection of the beam element have been presented in order to reduce the computational effort and bookkeeping. The procedure has been validated by comparison with the experimental and analytical results reported elsewhere and with FEM. The procedure can be readily extended for the analysis of composite building frames where saving in computational effort would be very considerable.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.194-195
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• 2022

The jointing of unsupported concrete on the parking lot floor is a process for cracking and stress relief due to concrete drying shrinkage and restraint, but curling occurs due to long-term drying shrinkage after the initial age. will be lowered Therefore, by using an expansion material and a shrinkage reducing agent, the dry shrinkage of concrete is realized to 200 με or less.

• Journal of the Korea Concrete Institute
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• 제23권3호
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• pp.289-294
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• 2011

The installation of joint is to prevent random cracking due to drying shrinkage stress of concrete slab. However contraction joint spacing is empirically implemented into slab constructions without detail calculation based on quantitative criteria. In this study, shrinkage strain of concrete due to concrete shrinkage stress was measured to suggest joint spacing based on the study results. The test environmental conditions were applied temperature of $15^{\circ}C$ and relative humidity of 60%. The design compressive strength used was 30 MPa and 40 MPa, which are currently used in concrete slab designs. The drying shrinkage test result was applied to drying shrinkage models (ACI 209R, CEB MC 90, B3, GL 2000 and Sakata). The results showed that the most appropriate model was ACI 209R model. Based on the research findings, quantitative contraction joint spacing locations were calculated.