• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.317-325
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• 2012

In this study, to evaluate the shrinkage behavior of ultra high performance fiber reinforced concrete (UHPFRC) under restrained condition, restrained shrinkage test was performed according to ring-test mostly used at home and abroad. Ring-test was performed with the various thicknesses and radii of inner steel ring to give different degree of restraint. Free shrinkage and tensile tests were carried out simultaneously to estimate the degree of restraint, stress relaxation, and shrinkage cracking potential. Test results indicated that the average steel strain and residual tensile stress were reduced as the thicker inner steel ring was used, whereas degree of restraint was increased. The steel strain, residual tensile stress and degree of restraint were hardly affected by the size of radius of inner ring. In the case of all ring specimens, shrinkage crack did not occur because the residual tensile stress was lower than the tensile strength. About 39~65% of the elastic shrinkage stress was relaxed by the sustained interface pressure, and the maximum relaxed stress was increased as the thicker inner ring was applied. Finally, the degree of restraint with age was predicted by performing non-linear regression analysis, and it was in good agreement with the test results.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.28-29
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• 2016

By Testing restrained shrinkage, it is possible to estimating the cracking tendency of concrete such as time to cracking, tensile stress and tensile creep. In this study, tensile creep properties of concrete under restraint shrinkage were investigation through comparison of specimens that JIS and AASHTO proposed. As a results, tensile creep strains in concrete ring specimens were 15% higher than those in uniaxial specimens.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.188-196
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• 2009

In Concrete, shrinkages occur like plastic shrinkage and drying shrinkage in the early age because of evaporation and transfer of moisture. Within the country, the crack test standardized by KS is used to test the drying shrinkage of the concrete by using the restricted drying shrinkage of Dumbbell type mold, but this test is for the cracking-point and the restricted shrinkage stress. Thus it is difficult to valuate the crack quantitative test. In this study, it is intended to develop the Flat-ring type restrained test method for the shrinkage deformation movement of the concrete and to provide the quantitative data for evaluating the cracks in concrete. And it suggest the proper specimen diameter and quantitative test method about shrinkage crack properties on Flat-ring type restrained test method. And Verified the suitability.

• 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.

• Fashion & Textile Research Journal
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• v.18 no.1
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• pp.113-119
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• 2016

The evolution of spinning technology was focused on improving productivity with good quality of yarns. More detail spinning technology according to mixing of various kinds of fibre materials on the air vortex spinning system is required for obtaining good quality yarns. This paper investigated the physical properties of air vortex yarns compared with ring and compact yarns using PTT/tencel/cotton fibres. It was observed that unevenness of air vortex yarns was higher than those of ring and compact yarns, which resulted in low tenacity and breaking strain of air vortex yarns. Initial modulus of air vortex yarns was higher than those of ring and compact yarns. Yarn imperfections of air vortex yarns such as thin, thick and nep were much more than those of ring and compact yarns. These poor yarn qualities of air vortex yarn were attributed to the fasciated yarn structure with parallel fibres in the core part of the air vortex yarn. However, yarn hairiness of air vortex yarns was less and shorter than those of ring and compact yarns. Thermal shrinkage of air vortex yarns were higher than that of ring yarns, which was caused by sensible thermal shrinkage of PTT fibres on the bulky yarn surface and core part of air vortex yarns.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.821-824
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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. It is possible to decide that specimen diameter is s 150mm with evaluating restrained shrinkage crack properties of concrete according to change of ring diameter in specimen. Also, effectiveness of test method according to mixing of PVA fiber is evaluated as part of a repeatability verification experiment of plat-ring type restrained test method using ring which diameter is 150mm. As a result, it is possible to measure the crack due to the plastic shrinkage which was occurred within 48hours at early age with plat-ring type restrained test method. Hereafter, it is considered that the study concerning environmental condition and mixing factor in plat-ring type restrained test method is need.

• Journal of the Korean Wood Science and Technology
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• v.33 no.2 s.130
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• pp.17-23
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• 2005

Juvenile and transitional-juvenile wood samples from loblolly pine (Pinus taeda) were immersed in water to investigate longitudinal and tangential swelling properties. Increment cores from twenty-six loblolly pine trees were sampled at breast height (1.37 m). Earlywood rings 5 and 9 were separated from the core, extracted, oven-dried and immersed in water at room temperature. The variance in longitudinal swell was significant for ring 5 compared to ring 9 (p = 0.001). It was found that tangential swell might predict longitudinal swelling of juvenile wood at ring 9 but not at ring 5. Poor correlation in ring 5 suggests that swelling response in younger juvenile wood may differ. The swell response at ring 5 did not follow the shrinkage models discussed in the literature while ring 9 adhered to the expected curve.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3535-3541
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• 2015

In this study, series of tests were performed for drying shrinkage characteristics of concrete with power type shrinkage reducing agent (SRA) and fly ash as a part of research to reduce drying shrinkage of concrete. Firstly, for the mechanical properties, a target strength was acquired securely. In the unrestraint shrinkage tests, the SRA decreased the drying shrinkage about $200{\mu}{\varepsilon}$. Lastly, in the ring tests, due to the tensile creep effect, the concrete with SRA showed the cracking times as much again as the concrete with ordinary Portland cement only did.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.5
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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.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.9-12
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• 2005

In this study, to investigate shrinkage and cracking behavior of 120MPa UHSC, free and restrained drying shrinkage test were performed. Three strength levels(50MPa, 80MPa, 120MPa) were used and the effect of mineral admixtures(fly ash, slag) on free and restrained shrinkage was investigated. From comparing the result of pin -penetration test with the result of ring test, Time-Zero was determined as initial set. Shrinkage test results show that autogenous shrinkage of UHSC was much higher than that of HSC, VHSC and fly ash delayed cracking age in UHSC by decreasing autogenous shrinkage. Additional free concrete rings(with restraint removed) were also tested to check the influence of the geometry of the specimens on free shrinkage. And then the relationship between free shrinkage and restrained shrinkage was investigated.