• Structural Engineering and Mechanics
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• 제2권4호
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• pp.403-412
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• 1994

The durability of concrete is related to the permeation characteristics of its near surface. An attempt was made to use the permeation characteristics namely, absorptivity, permeability and diffusivity, to predict the freeze/thaw resistance of concrete. Test results indicate that in general, there was a trend that freeze/thaw resistance of concrete was enhanced with improved absorptivity and diffusivity whilst the freeze/thaw resistance of normal concrete was found to have the best relationship with its intrinsic permeability. The latter method is therefore proposed to be adopted to predict freeze/thaw resistance of normal concrete. Since Figg air test is an inexpensive and simple test method that measures indirectly the intrinsic permeability of concrete, it is further proposed that it could be used as a quality control tool to assess, non-destructively, the freeze/thaw durability potential of in-situ concrete.

• Computers and Concrete
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• 제21권2호
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• pp.209-217
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• 2018

The dynamic compressive behavior of concrete after freezing and thawing tests are investigated by using the split Hopkinson pressure bar (SHPB) technique. The stress-strain curves of concrete under dynamic loading are measured and analyzed. The setting numbers of freeze-thaw cycles are 0, 25, 50, and 75 cycles. Test results show that the dynamic strength decreases and peak strain increases with the increasing of freeze-thaw cycles. Based on the Weibull distribution model, statistical damage constitutive model for dynamic stress-strain response of concrete after freeze-thaw cycles was proposed. At last, the fragmentation test of concrete subjected to dynamic loading and freeze-thaw cycles is carried out using sieving statistics. The distributions of the fragment sizes are analyzed based on fractal theory. The fractal dimensions of concrete increase with the increasing of both freeze-thaw cycle and strain rate. The relations among the fractal dimension, strain rates and freeze-thawing cycles are developed.

• Ocean Systems Engineering
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• 제2권2호
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• pp.159-171
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• 2012

Reinforced concrete structures in cold coastal regions are subjected to coupled effects of service load, freeze-thaw cycles and seawater corrosion. This would significantly degrade the performance and therefore shorten the service life of these structures. In the current paper, the mechanical properties of concrete material and the structural behaviour of eccentrically loaded reinforced concrete columns under multiple actions of seawater corrosion, freeze-thaw cycles and persistent load have been studied experimentally. Results show that when exposed to alternating actions of seawater corrosion and freeze-thaw cycles, the compressive strength of concrete decreases with the increased number of freeze-thaw cycles. For reinforced concrete column, if it is only subjected to seawater corrosion and freeze-thaw cycles, the load resistance capacity is found to be reduced by 11.5%. If a more practical service condition of reinforced concrete structures in cold coastal regions is simulated, i.e., the environmental factors are coupled with persistent loading, a rapid drop of 15% - 26.9% in the ultimate capacity of the eccentrically loaded reinforced concrete column is identified. Moreover, it is observed that the increase of eccentric load serves to accelerate the deterioration of column structural behavior.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.725-730
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• 2002

The durability of concrete involves resistance to freeze-thaw action, corrosion, permeation, carbonation, chemical attack and so on. Generally, properties of concrete have been well understood under the separate action of these deterioration mechanisms. However, in practice, the degradation of concrete usually is the result of combined action of physical and chemical attack and can be accelerated by the combined action of several deterioration mechanisms. In the present study, to evaluate the combined deterioration by freeze-thaw action and seawater attack, ground granulated blast-furnace slag or silica fume concrete with water or seawater as mixing water was exposed to 210 cycles of freeze-thaw action. Tests were conducted to determined the relative dynamic modulus of elasticity and compressive strength. Furthermore, The XRD, SEM and EDS analysis were performed on the deteriorated part of concrete due to freeze-thaw action and seawater attack.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.589-592
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• 2006

The durability of concrete involves resistance to freeze-thaw action, corrosion, permeation, carbonation, chemical attack and so on. Generally, properties of concrete have been well understood under the separate action of these deterioration mechanisms. However, in practice, the degradation of concrete usually is the result of combined action of physical and chemical attack and can be accelerated by the combined action of several deterioration mechanisms. In the present study, to evaluate the combined deterioration by freeze-thaw action and seawater attack, ground granulated blast-furnace slag or silica fume concrete with water or seawater as mixing water was exposed to 300 cycles of freeze-thaw action. Tests were conducted to determined the relative dynamic modulus of elasticity and compressive strength. Furthermore, The MIP analysis were performed on the deteriorated part of concrete due to freeze-thaw action and seawater attack.

• Advances in concrete construction
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• 제17권1호
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• pp.45-52
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• 2024

In this study, the fresh properties of paraffin-mixed concrete, compressive strength, resistance to frost damage, and resistance to composite deterioration under freeze-thaw and salt environment were investigated. The compressive strength of paraffin-mixed concrete was almost the same as that of unmixed concrete, and no decrease in strength was observed, unlike the concrete with entrained air in consideration of freeze-thaw resistance. Concerning the freeze-thaw resistance of paraffin-mixed concrete, the relative dynamic modulus of elasticity (RDME) did not decrease even without entrained air. In addition, no decrease in the RDME was observed in the combined deterioration with salt damage, and it was confirmed that the mass reduction was suppressed compared to the concrete without paraffin. The freeze-thaw resistance of concrete when paraffin is mixed may be improved due to the reduction in the amount of frozen water and the mixed paraffin particles exist in the concrete as pore fillers with a size of 200 ㎛ or less, which act as substitutes for air voids. This resulted in reduction of the apparent air void spacing and thereby relieving the pore pressure.

• Structural Engineering and Mechanics
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• 제86권5호
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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.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.957-960
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• 2006

In order to predict the accumulated damages by cyclic freeze-thaw, a regression analysis by the Response Surface Method (RSM) is used. RSM has merits when the other probabilistic simulation techniques can not guarantee the convergence of probability of occurrence or when the others can not differentiate the derivative terms of limit state functions, which are composed of random design variables in the model of complex system or the system having higher reliability. For composing limit state function, the important parameters for cyclic freeze-thaw-deterioration of concrete structures, such as water to cement ratio, entrained air pores, and the number of cycles of freezing and thawing, are used as input parameters of RSM. The predicted results of relative dynamic modulus and residual strains after 300 cycles of freeze-thaw for specimens show very good agreements with the experimental results. The RSM result can be used to predict the probability of occurrence for designer specified critical values. Therefore, it is possible to evaluate the life cycle management of concrete structures considering the accumulated damages by the cyclic freeze-thaw by the use of proposed prediction method.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.643-648
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• 2002

A research for recycling the demolished-concrete as concrete aggregate has been concerned in all over the world. There, however, are some problems that qualities of recycled aggregates are not only largely different, but also mechanical properties of recycled aggregate concrete decrease a little in comparison with that of natural aggregate concrete. In this study, the resistance of freezing and thawing of concrete using source-concrete recycled aggregate(SRN) and demolished-concrete recycled aggregate(DRA) was investigated. Futhermore a research for improvement of freeze and thaw durability of recycled aggregate concrete was performed. Relative dynamic modulus of elasticity of SRN and DRA recycled aggregate concrete was dropped 60% before 150 of freezing and thawing cycle, and was much lower than that of control concrete. Relative dynamic modulus of elasticity of recycled aggregate concrete was increased to decrease water-cement ratio, but the freeze and thaw durability of recycled aggregate concrete was not enough improved. Futhermore, when metakaolin and silica fume were repalced, the freeze and thaw durability of recycled aggregate concrete containg metakaolin was more improved than that of silica fume.

• 콘크리트학회논문집
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• 제17권5호
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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.