• Advances in concrete construction
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• v.6 no.2
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• pp.123-143
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• 2018

Self compacting concrete (SCC) has good flowability, passability and segregation resistance because of voluminous cementitious material & high coarse aggregate to fine aggregate ratio, and high free water availability. But these factors make it highly susceptible to shrinkage. Fibers are known to reduce shrinkage in concrete mixes. Until now for conserving cement, only pozzolanic materials are admixed in concrete to yield a SCC. Hence, this study compares the use of wollastonite micro fiber (WMF), a cheap pozzolanic easily processed raw mineral fiber, and flyash in yielding economical SCC for rigid pavement. Microsilica was used as a complimentary material with both admixtures. Since WMF has large surface area ($827m^2/kg$), is acicular in nature; therefore its use in yielding SCC was dubious. Binary and ternary mixes were constituted for WMF and flyash, respectively. Paste mixes were tested for compatibility with superplasticizer and trials were performed on a normal concrete mix of flexural strength 4.5 MPa to yield SCC. Flexural strength test and restrained shrinkage test were performed on those mixes, which qualified self compacting criteria. Results revealed that WMF admixed pastes have high water demand, and comparable setting times to flyash mixes. Workability tests showed that 20% WMF with microsilica (5-7.5%) is efficient enough in achieving SCC and higher flexural strength than normal concrete at 90 days. Also, stress rate due to shrinkage was lesser and time duration for final strain was higher in WMF admixed SCC which encourages its use in yielding a SCC than pozzolanic materials.

• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.261-268
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• 1998

Deflections due to shrinkage are frequently ignored in design calculation. Especially for thin member, shrinkage often causes considerable deformations as wellas appreciable stress changes. Several methods for computing shringkage curvature have been proposed by many researchers. Some of the approximte methods widely used in the recent years are the equivalent tensile force method, Miller's method and Branson's method. These methods were, however, somewhat oversimplified and could be too conservative in the case of well cured concrete structure. In this paper, an approximate method for computing shrinkage curvature and deflection is proposed. Curvature due to shrinkage is derived from the requirements of strain compatibility and equilibrium of a section and the age-adjusted effective modulus method. The proposed method is verified by comparison with several experimental measurements. The correlations between calculated and measured curvatures is very good.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.581-584
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• 2008

In this study, it is willing to present that fundamental data for proposing quantitatively shrinkage cracking evaluation method such as plat-ring type restrained test method. To examine suitable size of specimen of plat-ring type restrained test method, Evaluated concrete about restrained shrinkage crack properties of numerical analysis of 3D solid element using the MIDAS program, drying shrinkage deformation, restrained shrinkage stress, crack area and crack point with inside ring diameter of specimen in 100mm, 150mm, 200mm and high of Specimen in 30mm, 50mm after curing in condition of constant temperature and usual habit of temperature 20${\pm}$3$^{\circ}$C, humidity 60${\pm}$5%. As a result, it was available about suitable estimation with inside ring diameter of specimen in more than 150mm and high of Specimen in 50mm. Hereafter, it is considered that the study concerning environmental condition and mixing factor in plat-ring type restrained test method is need.

• Magazine of the Korea Concrete Institute
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• v.9 no.4
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• pp.197-205
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• 1997

The shrinkage of polymer concrete overlays to cement concrete causes interface shear, normal and axial stresses in the overlays. These can lead to deterioration of the polymer concrete overlays due to affection of adhesion polymer concrete and cement concrete. The shrinkage stress in the polymer concrete cause it to shorten and the shorting is measured: With the modulus of elasticity of the polymer concrete and strain known the stresses can be calculated. The purpose of this study is to provide the basic data of application of polymer concrete overlays such as bridge decks, highway and airport pavement repair and overlay materials. From the test results. It has been found that depending on the type polymer. overlay thickness, time after curing and temperature. the shrinkage stresses are eliminated by relaxation in time ranging from a few hours to a few days.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.127-130
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• 2000

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.647-650
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• 2003

Under sustained loads, the deformation of a structure gradually increase with time and eventually may be much greater than its instantaneous value, This inelastic and time-dependent deformation causes increase in deflection and curvature, redistribution of stress and internal action, In this paper, time-dependent analysis with creep and shrinkage of uncracked and cracked partially prestressed concrete flexural members is presented.

• Composites Research
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• v.27 no.4
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• pp.174-181
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• 2014

This study describes viscoelasticity analysis of carbon-fiber reinforced polymer matrix composite material. One of the most important problem during high temperature molding process is residual stress. Residual stress can cause warpage and cracks which can lead to serious defects of the final product. For the difference in thermal expansion coefficient and change of resin property during curing, it is difficult to predict the final deformed shape of carbon-fiber reinforced polymer matrix composite. The consideration of chemical shrinkage can reduce the prediction errors. For this reason, this study includes the viscoelasticity and chemical shrinkage effects in FE analysis by creating subroutines in ABAQUS. Analysis results are compared with other researches to verify the validity of the subroutine developed, and several stacking sequences are introduced to compare tested results.

• Textile Coloration and Finishing
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• v.1 no.1
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• pp.54-62
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• 1989

The woven fabric composed of nylon 6 filaments was treated with aqueous solutions (20, 30, 40, 50, 60%) of formic acid at 3$0^{\circ}C$ for 10 minutes under unrestrained condition, and the shrinkage behavior and some kinds of properties were examined. The shrinkages of the constituent yarns and fabric were increased with formic acid concentration, but they were lower than that of the original filaments because of fabric-structural factors. And the shrinkage of the warp was lower than that of the weft because of the residual stress from weaving process. By the restraint forces such as fabric-structural factors and residual stress, the constituent filaments were damaged partially at 60% of formic acid concentration and the degree of damage on the warp was greater than on the weft. And though the fabric count were increased overall, the spacing between the warps was decreased prior to the weft and eliminated nearly at 60% of formic acid concentration. The thickness, tensile strength, elongation, and handle value of fabric were increased overall with formic acid concentration excepting that the tensile strength for both the warp and weft directions and the elongation for the warp direction were decreased instead by the damage of yarns. But the crease recovery was decreased except the case of the weft direction at 60% of formic acid concentration.

• Polymer(Korea)
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• v.27 no.5
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• pp.477-483
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• 2003

The structure development of drawn poly(trimethylene terephthalate) PTT as a function of draw down ratio and drawing temperature was studied. The special effort was made to find out the effect of structural development on thermal properties and crystallinity in drawn PTT. The changes in shrinkage ratio and mechanical properties were understood base on the level of crystallinity and orientation of the drawn PTT. The stress induced crystallization caused the increase in glass transition temperature and the decrease in cold crystallization temperature and enthalpy. The crystallinity and orientation were dependent upon the level of applied stress level as well as chain flexibility at high drawing temperature. The drawing resulted in the increase of shrinkage ratio but it was minimized by increasing of crystallinity. The development of orientation resulted in increasing modulus and tensile strength while decreasing elongation at break.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.461-466
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• 2013

This paper examines the characteristics of butt welding joint shrinkage for shipbuilding and marine structures main plate. The shrinkage strain of butt welding joint which is caused by the process of heat input and cooling, results in the difference between dimensions of the actual parent metal and the dimensions of design. This, in turn, leads to poor quality in the production of ship blocks and reworking through period of correction brings about impediment on improvement of productivity. Through experiments on butt welding joint's shrinkage strain on large structures main plate, the deformation of welding residual stress in the form of I, Y, V was obtained. In addition, the results of experiments indicate that there is limited range of shrinkage in the range of 1 ~ 2 mm in 11t ~ 21.5t thickness and the effect of heat transfer of weld appears to be limited within 1000mm based on one side of seam line so there was limited impact of weight of parent metal on the shrinkage. Finally, it has been learned that Shrinkage margin needs to be applied differently based on groove phenomenon in the design phase in order to minimize shrinkage.