• Title/Summary/Keyword: Freezing and thawing test

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Effect of Cyclic Freezing-Thawing on Compressive Strength of Decomposed Granite Soils (동결-융해 반복작용으로 인한 화강풍화토의 압축강도 특성 변화에 관한 연구)

  • Yoo, Chung-Sik;Shin, Boo-Nam
    • Journal of the Korean Geosynthetics Society
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    • v.10 no.1
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    • pp.19-28
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    • 2011
  • This paper presents the results of an investigation into the effect of cyclic freezing-thawing on the compressive strength characteristics of decomposed granite soils. A plane strain compression (PSC) tests were performed on a series of test specimens with different freezing-thawing cycles and fine contents to investigate the change in compressive strength under the process of freezing-thawing cycles. Also performed were scanning electron microscope (SEM) tests to investigate the change in structural rearrangement from a micro-scale point of view. The test results showed that the soil particles tend to conglomerate when subject to cycles of freezing and thawing, and that the soil with less fines exhibited decreased shear strength due to the cyclic freezing-thawing while the soils with a larger fine content showed the opposite trend.

Physicochemical Properties of Cooked Rice as Affected by Cooking Methods and Thawing Conditions (취반 및 해동방법에 따른 쌀밥의 이화학적 특성)

  • Ha, Joo-Young;Lee, Jong-Mee
    • Journal of the Korean Society of Food Culture
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    • v.20 no.2
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    • pp.253-260
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    • 2005
  • This study was conducted to investigate performance of methods for cooking and thawing frozen cooked rice to retard retro-gradation of cooked rice. For this research, That was executed rice's physicochemical and sensory characteristics test through the way of boiling rice or thawing, and found out best way for retro-gradation and taste. This study showed the rice cooked by pressure rice pot has less dehydration during freezing and thawing, and thawed rice by micro wave has less dehydration. Repetition of freezing and thawing resulted increasing of hardness and chewiness, and decreasing of adhesiveness and cohesiveness. The rice cooked by convotherm oven or pressure rice pot has less increased hardness while freezing and thawing. Adhesiveness was superior when rice was cooked by pressure rice pot. The rice thawed by microwave had more hardness than thawed in room temperature.

Fatigue Characteristics of Asphalt Concrete Based on compacted Density (아스팔트 콘크리트의 다짐도에 따른 피로 특성)

  • 김광우;이병덕;박용철
    • Proceedings of the Korea Concrete Institute Conference
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    • 1994.10a
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    • pp.205-210
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    • 1994
  • This study was conducted to evaluate performance of asphalt concretes under various densities, using Marshall specimens before and after freezing-and-thawing treatment. Six different compaction blows per side (20, 30, 40, 50, 60, 70 blows) were applied to specimens to produce different densities. Test results showed that the lower density specimens had the weaker resistance to freezing-and-thawing treatment. The density was an index of retaining fatigue life and displacement after freezing-and-thawing. Therefore, poor compaction in pavement was considered to be a major cause of early distress mechanisms such as rutting, ravelling and cracking, which were resulted in a reduced service life.

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Studies on the Factors Influencing Survival Rates of Frozen Bovine Demi-Embryos (소 동결분할배의 생존선에 영향을 미치는 요인에 관한 연구)

  • 김상근;남윤이;이만휘;현병화
    • Korean Journal of Animal Reproduction
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    • v.21 no.3
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    • pp.287-292
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    • 1997
  • This study was carried out to investigate the effects of concentration and kinds of cryoprotectants, equilibraction time, thawing temperature and time, sucrose concentration on the survival rates of frozen bovine demi-embryos. The bovine demi-embryos following dehydration by cryoprotectants a various concentration of sucrose were freezed by cell freezer and thawed in 3$0^{\circ}C$ water bath. Survival and in vitro developmental rates was defined as development rates on in vitro culture or FDA-test. The results are summarized as follows : 1. The high survival rates of demi-embryos after frozen-thawing in freezing medium was attained 2.0M glycerol. The high survival rates of demi-embryos after frozen-thawing in freezing medium was obtained using single cryoprotectant(25.0~30.0%) than mixed cryoprotectants(16.7~19.0%). 2. The survival rates of demi-embryos after frozen-thawing in freezing medium added 1.5M, 2.0M glycerol+0.25M sucrose(37.5~33.3%) were higher survival rates than those of sucrose concentration of 0.50, 0.75M(12.5~26.7%). 3. The equilibration time on the survival rates of demi-embryos was attained after short period of time(30.0~35.0%) in the freezing medium higher than long period of time(21.1%). 4. The thawing temperature on the survival rates of demi-embryos was attained at 3$0^{\circ}C$ of thawing temperature(26.7~40.0%) higher than $25^{\circ}C$ or 37$^{\circ}C$ of thawing temperature(13.3~20.0%). 5. The thawing time on the survival rates of demi-embryos was attained at 1~5 minutes of thawing time(26.7~33.3%) in the freezing medium higher than 10 minutes of thawing time(13.3~18.8%).

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An Experimental Study on the Resistance of Concrete Included Rice Husk Ash Against Rapid Freezing and Thawing (왕겨재를 혼입한 콘크리트의 동결융해 저항성에 관한 실험적 연구)

  • 이준구;박광수;이응찬;김한중
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 1999.10c
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    • pp.294-300
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    • 1999
  • After researching the physical properties of the concrete included Rice Husk Ash(RHA concrete) and workability of fresh concrete admixed RHA, we have tested durability of RHA-concrete against freeaing and thawing in the winter using rapid freezing and thawing test method(KS F 2456) . There aretwo hypotheses to explain the failure mechanism of a freezing and thawing action. First, the hydraulic pressure in the pores of freezing concrete make an internal stress of concrete structures outbreaking micro crack in the face of concrete, Second, Frost action causing damage to cement paste repeatedly come from soil frost action, freezing water in the capillaries. Initial Relative Dynamic Modulus of Elasticity (DME) was biggest in cae of unit binder weight 600kgf/㎥ and relative dynamic modulus of elasticity increased until 300cycles. In general , initial relative DME was proportional to unit binder weight . Relative DME was decreased in proportion to unit binder weight in the case of 300, 400, 500kgf/㎥ , but relative DME fo the others remained more than 90% until 300 cycles. It was not good effect of intermixed RHA to concrete in case of below unit binder weight 300kgf/㎥ and the resistance of freezing and thawing was not good either.

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The Compressive Strength and Durability Characteristics of Lime-Cement-Soil Mixtures (석회-시멘트 혼합토의 압축강도 및 내구 특성)

  • Oh, Sang-Eun;Yeon, Kyu-Seok;Kim, Ki-Sung;Kim, Yong-Seong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.54 no.1
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    • pp.83-91
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    • 2012
  • In this study, the compressive strength characteristics of lime-cement-soil mixtures, composed of lime, soil, and a small amount of cement, were investigated by performing the unconfined compression tests, the freezing and thawing tests, the wetting and drying tests and the permeability tests. The specimens were made by mixing soils with cement and lime. The cement contents were 0, 6, 8 and 10 %, and the lime contents were 2, 4, 5, 10, 15 and 20 % in weight. Each specimen was cured at constant temperature in a humidity room for 3, 7 and 28 days. The compressive strength characteristics of the lime-cement-soil mixtures were then investigated using the unconfined compression tests, freezing and thawing tests and the wetting and drying tests. Based on the test results, a discussion was made on the applicability of the lime-cement-soil mixtures as a construction material.

Freezing-Thawing Resistance of Fiber Reinforced Polymers in Strengthening RC Members (구조보강용 FRP 복합체의 동결용해 저항성 평가 연구)

  • You, Young-Chan;Choi, Ki-Sun;Kim, Keung-Hwan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.1
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    • pp.182-189
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    • 2010
  • The strengthening performance of FRPs(Fiber Reinforced Polymers) is directly affected by the environmental conditions such as freezing-thawing and moisture because FRPs are usually bonded on the concrete surface. It is, therefore, strongly required to evaluate a durability of bond between FRPs and concrete as well as FRP materials itself. The freezing-thawing resistance of FRPs is evaluated in this study with the variables of freezing-thawing conditions, types of FRP and freezing-thawing cycles. From the test results, it is found that tensile strength and pull-off strength of CFRP are not affected by the freezing-thawing. On the other hands, those of GFRP show a little degradation because of continuous water immersion during thawing process. But, cautions are needed on the bond durability between FRPs and concrete in case of continuous water supplying from adjacent to the concrete.

An Experimental Study on the Performance of RC Beam according to the Rapid Freezing and Thawing Test Method in the Air (기중 급속 동결 융해 시험 방법에 따른 철근콘크리트 보의 성능 실험 연구)

  • Kim, Sang-Woo;Lee, Dong-Ju;Kim, Kyeong-Min;Kim, Jin-Sup
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.4
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    • pp.46-55
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    • 2021
  • Concrete structures can cause various problems as the number of common years increases when exposed to external extreme climate conditions. Among these problems, freezing and thawing occur due to the action of extreme climate factors such as heavy rain and heavy snow, which have become the most problematic in recent years. In this study, we present a rapid freezing and thawing test method of concrete in the air, referring to KS F 2456, as Seoul exhibits very dry weather during the period of freezing and thawing. Concrete test specimens and RC beams were fabricated to perform rapid freezing and thawing of 0, 100, 200, and 300 cycles, and the performance evaluation confirmed the degradation of each subject in material and member units. The design strength of 24 MPa, which performs rapid freezing and thawing in the air up to 300 cycles, decreases by 5.24 MPa (21%), and as rapid freezing and thawing in the air increases the stress burden on reinforced concrete bending members, reducing the energy absorption (dissipation) ability of structures due to earthquakes.

Characteristics of Environment-Friendly Porous Polymer Concrete for Permeable Pavement

  • Kim, Young-Ik;Sung-Chan, Yong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.47 no.7
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    • pp.25-33
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    • 2005
  • This study was performed to develop environment-friendly porous polymer concrete utilizing recycled aggregates [RPPC] for permeable pavement of uniform quality with high permeability and flexural strength as well as excellent freezing and thawing resistance. The void ratios of RPPC are in the range of 15$\sim$$24\%$, showing the tendency that it is reduced to a great extent as the mixing ratio of the binder increases. The compressive and flexural strength of RPPC are in the range of 19$\sim$26 MPa and 6.2$\sim$7.4 MPa, respectively. Also, it shows a tendency to increase as the mixing ratio of the binder and filler increases. The permeability coefficients of RPPC are in the range of $6.3\times$$10_{-1}$$\sim$$1.5\times$$10_{-2}$cm/s. The flexural loads of RPPC are in the range of 18$\sim$32 KN. The weight reduction ratios obtained from the test for freezing and thawing resistance are in the range of 1.1$\sim$$2.4\%$ after 300 cycles of repeated freezing and thawing of the specimen for all mixes. The relative compressive strengths of RPPC after 300 cycles of freezing and thawing against the compressive strength before freezing and thawing test are in the range of 89$\sim$$96\%$.

Evaluation of Stripping and Rutting Properties of CRM Modified Asphalt Mixtures (CRM 개질아스팔트 혼합물의 소성변형 및 박리저항 특성)

  • Doh, Young-S.;Park, Tae-W.;Kim, Hyun-H.;Kim, Kwang-W.
    • International Journal of Highway Engineering
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    • v.9 no.4
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    • pp.149-158
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    • 2007
  • Evaluation of the asphalt mixture modified with crumb rubber modifier(CRM) was performed to estimate possibility of using it as a paying material. OACs(optimum asphalt content) of CRM modified asphalt mixtures by dry process and wet process were determined by Marshall mix design and Wheel tracking test and moisture susceptibility test by freezing and thawing were carried out with CRM modified asphalt mixtures at OACs. The results from these tests, resistance of permanent deformation of CRM modified asphalt mixtures were superior to one of AP-5 while showing very low resistance of moisture sensitivity by freezing and thawing. This means that CRM modified asphalt mixtures are very sensitive to freezing and thawing. However, CRM modified asphalt mixture with anti-stripping material showed high improvement to resistance of moisture susceptibility by freezing and thawing. Therefore, it is recommended that when CRM mixtures were used in domestic, CRM modified asphalt mixtures should be with prevention against freezing and thawing resistance by moisture susceptibility.

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