• Journal of the Korea Concrete Institute
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• v.19 no.4
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• pp.457-465
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• 2007

In this paper, polymer-modified repair materials using polymer dispersions with six repair methods are prepared with various polymer-cement ratios, and tested for compressive and flexural strengths through each curing condition such as dry cure, water cure, and freezing and thawing cyclic action. And, the adhesive interface between the polymer-modified mortar and mortar substrate is observed by a scanning electron microscope. From the test results, the compressive and flexural strengths of cement mortar repaired by polymer-modified mortar are improved with a rise in the polymer-cement ratio regardless of the type of polymer and curing conditions. Such an improvement in the strengths of polymer-modified repair materials to ordinary cement mortar is explained by the high adhesion of polymer-modified mortar. Strength reduction of polymer-modified repair materials after freezing and thawing cyclic actions is recognized, but it is lower than that of unmodified mortar. Especially, cement mortar repaired by polymer-modified mortar with a St/BA emulsion has good strength properties compared with those of SBR latex and PA emulsion. Accordingly, it is judged that polymer-modified mortars with a St/BA emulsion are possible to use as repair materials to ordinary cement mortar and concrete.

• Journal of the Korean Geotechnical Society
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• v.19 no.5
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• pp.69-78
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• 2003

In order to investigate the dynamic behavior of weathered granite soils before and after freezing-thawing, cyclic triaxial tests were conducted for the specimens not only with the variation of silt contents within 20% but with plasticity index within 20%. As the results, the dynamic shear modulus of weathered granite soils decreased with increasing silt contents. However, the change in damping ratio was negligible. The influence of freezing-thawing on shear modulus and damping ratio was minimal for the granite soils with variation of silt contents. For the case of the weathered soils with variation of plasticity index, the shear modulus increased with plasticity index within 20%, while the modulus decreased remarkably after freezing-thawing.

• Journal of The Geomorphological Association of Korea
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• v.18 no.3
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• pp.21-36
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• 2011

Rock Weathering is a basic of geomorphological evolution as a preparation of materials. Of those, frost shattering has traditionally been considered as the operative process causing rock breakdown in cold regions as well as temperate zone. Each Granite(fresh rock, semi-weathered), Gneiss, Limestone, Dolomite was prepared slab specimens in ten, repeated freeze-thaw cycles of 180 under the -25℃~+30℃, and the changes was observed in physical properties and weathering aspect. Rock shattering was more active in waterlogging conditions rather than atmospheric and soil conditions. Limestone and Dolomite that high porosity are most severely crushed. Gneiss, regardless surface of the crack, joint, fissure and has a lowest rock strength(SHV), was even though no physical changes and their weathering product do not generate, has a very high resistance to weathering.

• Journal of the Korean GEO-environmental Society
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• v.17 no.5
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• pp.37-46
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• 2016

In order to determine the variability of environmental characteristics of lightweight air-foamed soil using marine clay according to freezing-thawing and soaking conditions, unconfined compressive strength of the lightweight air-foamed soil samples made by changing the amount of cement under curing conditions of outdoor low temperature, underground or indoor wetting were observed. Compressive strength was not increased under freezing-thawing (temperature range of $-9.1^{\circ}C{\sim}17.2^{\circ}C$) regardless of the amount of cement but the more cement using, it was increased rapidly by underground curing conditions within 30 cm beneath ground level. Therefore, it is necessary to install insulation layer cutting off exterior cold air after construction of lightweight air-foamed soil in condition of freezing-thawing. Bulk density was increased too small under the long-time soaking condition, it tended to decrease rapidly when samples were dried up and had below 6% of water contents. But variability of compressive strength and bulk density was very small for preventing drying and keeping its wet state. The lightweight air-foamed soil that installed beneath ground water level or covered by soil can be evaluated as a long-term reliable construction material.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.587-593
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• 2019

This study were subjected to accelerated weathering test under freeze-thaw and pressure conditions to observe initiation and propagation of cracks using CLSM. Applied stress was set at 50 MPa, 55 MPa, 70 MPa for 3 samples each by using compressor and freeze-thaw experiment was conducted while samples maintained that condition. In freeze-thaw experiments, a temperature range was set to -20~40℃ which was 1 cycle for 6 hours. The freeze-thaw cycle was composed of time which reached to set temperature for 1 hour and holding time for 2 hours. On the basis of this cycle, surface of samples was observed by CLSM after each 20 freeze-thaw cycle. From this research, according to increase freeze-thaw cycle, there were 7, 10, 19 each cracks and High pressured sample's accumulate length was longer than low pressured sample's. High pressured sample's crack velocities were also faster than low pressured sample's which were calculated by accumulate length and freeze-thaw cycle.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.53-58
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• 2017

FRP Hybrid Bar, composed of an embedded steel and the coated composites with epoxy and glass fiber, is an effective construction material with tension-hardening performance and lightweight. The epoxy exposed to UV(Ultra Violet Rays) and FT(Freezing and Thawing) action easily shows a surface deterioration, which can cause degradation of bonding strength between inside-steel and outside-concrete. In the present work, surface inspection for 3 different samples of normal steel, FRP Hybrid Bar before UV, and FRP Hybrid Bar after UV test was performed, then concrete samples with 3 reinforcement types were prepared for accelerated FT test. Through visual inspection on 3 typed reinforcement, no significant deterioration like chalking was evaluated. The results from FT test to 120 and 180 cycles showed FRP Hybrid Bar exposed to UV test has higher bonding strength than normal steel by 106.3% due to enlarged bond area by silica coating. The 3 cases showed a similar bond strength tendency with increasing FT cycles, however a relatively big deviations of bond strength were evaluated in FRP Hybrid Bar after UV test due to loss of silica coating.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1097-1100
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• 2008

The purpose of this study to investigate the bond strength of recycled coarse aggregate concrete deteriorated by freezing and thawing. Concrete specimens with recycled coarse aggregate representing lower limit of the quality standard (water absorption : 3.0%, specific gravity : $2.5g.cm^3$) were manufactured and tested. The replacement ratio (0, 30, 60 and 100%) of recycled coarse aggregate and freezing-thawing cycles were considered in this test. From the test results, it was found that the bond strength of normal strength concrete is not affected by the replacement ratio of recycled coarse aggregate under freezing and thawing conditions. Also, the bond strength of the natural and recycled coarse aggregate concrete using AE admixtures was not decreased by frost action.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.13-21
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• 2011

In seasonal frozen areas with climatic features, which have a temperature difference in the winter and thawing season, changes of mechanical properties of the soil in the zone could be seen between the freezing and thawing surface. In particular, in soil with many fine particles, a softening of the roadbed usually occurs from frost and thawing actions. The lower bearing capacity is a rapidly progressive the softening of roadbed, and occurred a mud-pumping by repeated loading. In this study, the three kind of sandy soil with contents of fine particles were conducted by directly shear box test with the number of cyclic in freeze-thawing and the water content of soil. Subsequently, the relationship between the shear strength and freeze-thaw cycling time was obtained. The shear strength was decreased with the increase of the freeze-thaw cycling time. A shear stress deterioration of the soil with power function modal is proposal.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1499-1508
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• 2013

Freeze-thaw tests were performed on gneiss samples collected from Terra Nova Bay, Antarctica in order to examine the engineering properties of rocks with slightly weathered (SW) and moderately weathered (MW). The tests were conducted under temperature ranging from $20{\pm}2^{\circ}C$ to $-20{\pm}2^{\circ}C$. A cycle of test consisted of 5 hours of freezing followed by another 5 hours of thawing under full saturation. In this paper, total 200 cycles of freeze-thaw test were performed with measurements of porosity, absorption, ultrasonic velocity, and shore hardness per each 20 cycle and that of uniaxial compressive strength (UCS) per each 50 cycle. The UCS of the SW rocks approximately decreased 0.07 MPa per a single cycle, while that of MW rocks decreased around 0.2 MPa per a single cycle. During the 200 cycles of SW rocks, the absorption increased from 0.23% to 0.39%, the P-wave velocity decreased from 4,054 m/s to 3,227 m/s and S-wave velocity decreased from 2,519 m/s to 2,079 m/s. Similarly, those of MW rocks changed from 0.65% to 1.6%, 3,207 m/s to 2,133 m/s and 2,028 m/s to 1,357 m/s. In conclusion, it was inferred that the properties of SW rocks experienced approximately 200-300 cycles of freeze-thaw process become close to those of MW rocks.

• Journal of the Korea Institute of Building Construction
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• v.16 no.6
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• pp.595-601
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• 2016

The insulation performance of the insulation currently used in building structures is reflected only during design based on initial performance and the reduction in heat insulation performance due to the degradation of long-term durability is not reflected. This study reviewed the degradation of heat insulation performance due to the durability degradation of insulating materials through the accelerated durability test. The study findings showed that the foamed polystyrene insulation bead method did not show performance degradation due to aging in the standard environmental condition and laboratory accelerated test condition but the performance is degraded in the freeze-thaw test condition. On the other hand, in the case of the extrusion method, the degradation of the heat insulation performance was less in the freeze-thaw test condition, but the rapid performance degradation was caused by the release of the internal gas at the beginning of aging. In addition, the hard polyurethane foam insulation showed better initial insulation performance than other insulation materials, but the performance was found to be degraded somewhat under laboratory accelerated test conditions and freeze-thaw test conditions.