• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.13.2-17
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• 2003

When fresh concrete is exposed to low temperature, the concrete may suffer frost damage due to freezing at early ages and strength development may be delayed. One of the solution methods to resolve these problems is to lower freezing temperature of concrete by the use of chemical admixture called Accelerators for Freeze Protection. In this study, it was the results of appling cold weather concrete using Accelerator for Freeze Protection in the Daewoo Trump world field. Before the application of the cold weather concrete using accelerator for freeze protection, we executed the some test in the laboratory and mock-up test in the field. We examined the manifestation of compressive strength complying with the amount of Accelerators for Freeze Protection and curing conditions, and then made a selection of most suitable amount of Accelerators for Freeze Protection.

• Asian-Australasian Journal of Animal Sciences
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• v.17 no.9
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• pp.1291-1295
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• 2004

Histology and transmission electron microscopy studies were carried out on buffalo muscles that were subjected to repeated freeze-thaw cycles at -10 and $-18^{\circ}C$. In the first freeze thaw cycle ($-10^{\circ}C$) structures of muscle showed slight change and closely resembled to those of normal muscle. There were frequent gaps in the half way across the fibres and some cracks in individual fibre were also noticed in second freeze thaw cycle. In the muscle frozen at $-18^{\circ}C$, more pronounced shrinkage with extensive damage of fibres with tearing was observed. The interfibrillar gaps were wider, shrinkage and tearing of the fibres were more distinct after second freeze-thaw cycle. After the second cycle, the interior portion showed large scale degradation of the ultrastructure. Our studies of buffalo muscle showed that under the proper condition, little structural damage takes place in the meat histology and ultrastructure under repeated freeze-thaw conditions. This study adds continued weight to the evidence that limited freeze-thaw cycles will not deteriorate the quality of meat.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.4
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• pp.269-275
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• 2000

It is well recognized that damage resulting from freeze-thaw cycles is a serious problem causing deterioration and degradation of concrete. In general, freeze-thaw cycles change the microstructure of the concrete ultimately leading to internal stresses and cracking. In this study, a new method for one-sided stress wave velocity measurement has been applied to evaluate freeze-thaw damage in concrete by monitoring the velocity change of longitudinal and surface waves. The freeze-thaw damage was induced in a $400{\times}350{\times}100mm$ concrete specimen in accordance with ASTM C666 using s commercial testing apparatus. A cycle consisted of a variation of the temperature from -14 to 4 degrees Celsius. A cycle takes 4-5 hours with approximately equal times devoted to freezing-thawing. Measurement of longitudinal and surface wave velocities based on one-sided stress wave velocity measurement technique was made every 5 freeze-thaw cycle. The variation of longitudinal and surface wave velocities due to increasing freeze-thaw damage is demonstrated and compared to determine which one is more effective to monitor freeze-thaw cyclic damage progress. The variation in longitudinal wave velocity measured by one-sided technique is also compared with that measured by the conventional through transmission technique.

• Structural Engineering and Mechanics
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• v.86 no.5
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• pp.663-671
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• 2023

Freeze-thaw cycles induce strength loss at the frozen soil-concrete interface and deterioration of bonding, which causes construction engineering problems. To clarify the deterioration characteristics of the interface under the freeze-thaw cycle, a frozen soil-concrete sample was used as the research object, an interface scanning electron microscope test under the freeze-thaw cycle was carried out to identify the micro index information, and an interface shear test was carried out to explore the loss law of interface shear strength under the freeze-thaw cycle. The results showed that the integrity of the interface was destroyed, and the pore number and pore size of the interface increased significantly with the number of freeze-thaw cycles. The connection form gradually deteriorates from surface-to-surface contact to point-to-surface contact and point-to-point contact, and the interfacial shear strength decreases the most at 0-3 freeze-thaw cycles, with small decreases from to 3-8 cycles. After 12 freeze-thaw cycles, the interfacial shear strength tends to be stable, and shear the failure occurs internally in the soil.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.6
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• pp.395-399
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• 2000

Five different freeze-dried recombinant bioluminescent bacteria were used for the detection of cellular stresses caused by endocrine disrupting chemicals. These strains were DPD2794 (recA::luxCDABE), which is sensitive to DNA damage, DPD2540 (fabA::luxCDABE), sensitive to cellular membrane damage, DPD2511 (katG::luxCDABE), sensitive to oxidative damage, and TV1061 (grpE::luxCDABE), sensitive to protein damage. GC2, which emits bioluminescence constitutively, was also used in this study. The toxicity of several chemicals was measured using GC2. Damage caused by known endocrine disrupting chemicals, such as nonyl phenol, bisphenol A, and styrene, was detected and classified according to toxicity mode, while others, such as phathalate and DDT, were not detected with the bacteria. These results suggest that endocrine disrupting chemicals are toxic in bacteria, and do not act via an estrogenic effect, and that toxicity monitoring and classification of some endocrine disrupting chemicals may be possible in the field using these freeze-dried recombinant bioluminescent bacteria.

• Geomechanics and Engineering
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• v.14 no.4
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• pp.307-314
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• 2018

Strength of loess that experienced cyclic freeze and thaw is of great significance for evaluating stability of slopes and foundations in loess regions. This paper takes the frequently encountered loess in the Northwestern China as the study object and carried out three kinds of laboratory tests including freeze-thaw test, direct shear test and SEM test to investigate the strength behaviors of loess after cyclic freeze and thaw, and the correlation with meso-level changes in soil structure. Results show that for loess specimens at four dry densities, the cohesion decreases with freeze-thaw cycles until a residual value is reached and thus an exponential equation is proposed. Besides, little change in the angle of internal friction was observed as freeze-thaw proceeds. This may depend on the varying of soil structure, based on which a clue can be found from the surface morphology and mesoscopic scanning of loess specimens. Clearly we observed significant changes in surface morphology of loess and it tends to aggravate at higher water contents or more cycles of freeze and thaw. Moreover, freeze-thaw cycling leads to obvious changes in the meso-structure of loess including lowering the particle aggregates and increasing both the proportion of fine particles and porosity area ratio. A damage variable dependent on the ratio of porosity area is introduced based on the continuum damage mechanics and its correlation with cohesion is discussed.

• Journal of the Korean GEO-environmental Society
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• v.14 no.3
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• pp.35-40
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• 2013

In most cases, Geotechnical Structures installed in freezing areas require extra countermeasures for reducing freeze damage. However, in terms of domestic tunnels, studies and case reports for geotechnical structures such as tunnels and retaining walls are not fluently carried out, causing lack of research about ways to decrease freeze damage. For these causes, domestic design criteria about structures does not specifically institutionalization for geotechnical structures. This research have done on-site investigation about tunnels, cut slopes and retaining walls. Also, this research includes the process of analyzing the histories of maintenance for class 1 and class 2 structures that happened in the past 40 years, studying characteristics of structure's maintenance and reinforcement in different areas with different climate. As the result, it was analyzed that domestic geotechnical structures showed need for longer maintenance and reinforcement that are located in Gangwon mountain area, Gangwon north region and Gyeonggi north region where the temperature is relatively low. This research can be concluded in need for revision of design criteria for structures located in freeze damage area.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.857-868
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• 2005

This paper deals with the accumulated damage in concrete structures due to the cyclic freeze-thaw as an environmental load. The cyclic ice body nucleation and growth processes in porous systems are affected by the thermo-physical and mass transport properties, and gradients of temperature and chemical potentials. Furthermore, the diffusivity of deicing chemicals shows significantly higher value under cyclic freeze-thaw conditions. Consequently, the disintegration of concrete structures is aggravated at marine environments, higher altitudes, and northern areas. However, the properties of cyclic freeze-thaw with crack growth and diffusion of chloride ion effects are hard to be identified in tests, and there has been no analytic model for the combined degradations. The main objective is to determine the driving force and evaluate the reduced strength and stiffness by freeze-thaw. For the development of computational model of those coupled deterioration, micro-pore structure characterization, pore pressure based on the thermodynamic equilibrium, time and temperature dependent super-cooling with or without deicing salts, nonlinear-fracture constitutive relation for the evaluation of internal damage, and the effect of entrained air pores (EA) has been modeled numerically. As a result, the amount of ice volume with temperature dependent surface tensions, freezing pressure and resulting deformations, and cycle and temperature dependent pore volume has been calculated and compared with available test results. The developed computational program can be combined with DuCOM, which can calculate the early aged strength, heat of hydration, micro-pore volume, shrinkage, transportation of free water in concrete. Therefore, the developed model can be applied to evaluate those various practical degradation cases as well.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.399-407
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• 2010

The flexural behaviors of two types of beam members exposed to freeze-thaw cycles were evaluated. This study aims to examine the effect of freeze-thaw cycles on the behavior characteristics of reinforced concrete (RC) beams. For the purpose, a part of the beam specimens were damaged until yielding of tension reinforcement was reached, before they were exposed to 150 and 300 cycles of freeze-thaw. Cyclic tests, as well as monotonic tests, were conducted to evaluate the stiffness degradation characteristics when same cycle is repeated. The material tests showed that relative dynamic modulus of concrete exposed to 300 cycles of freeze-thaw moderately decreased to 86.8% of normal concrete, indicating that concrete used in this study has good durability against freeze and thaw damage. The results of monotonic tests showed reduction of flexural strength, ductility and stiffness of the beam specimens exposed to freeze-thaw cycles compared with those of the control speciments. In particular, BDF13 specimens, which had been subjected to artificial cracking damage, did not showed enough flexural strength to satisfy nominal moment required by current concrete structure design code. In the monotonic tests results, BF75 specimens exposed to freeze-thaw cycles showed 10% or more cyclic stiffness degradation. Therefore, it was thought that deformation of concrete in compression have to be considered in design process of members under cyclic load, such as seismic device.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.29-38
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• 2014

PURPOSES : The purpose of this study is to evaluate moisture susceptibility of a dense graded and an open graded asphalt mixtures by the method of AASHTO T-283. METHODS : To simulate moisture damage of asphalt pavements with continuously rainfall during summer rainy season, the dense graded and the open graded asphalt mixtures were immersed in water for 15 days and were measured the weight and the change of strength. Also, the mixtures were performed five freeze-thaw cycles to simulate moisture damage of the mixtures by freeze-thaw during winter and were measured the change of strength. The degradation characteristics model was used to analyze the relationship between strength and moisture damage. RESULTS : According to the results, the dense graded and the open graded asphalt mixtures were shown in the similar trends of the strength changes by immersion time and freeze-thaw cycle. However, the moisture damage reduction of open graded asphalt mixture was more sensitive in early phase than that of dense graded asphalt mixture.