• Journal of the Korea Concrete Institute
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• v.14 no.5
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• pp.708-717
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• 2002

Durability is a major concern in the design and construction of concrete structures which are located in the sea environments. In particular, the combined action of chlorides, sulfates, and carbonation nay influence greatly the deterioration behavior of concrete structures. The purpose of the present study is to explore the diffusion characteristics of chloride ions in concrete structures under combined deterioration conditions. The present test results indicate that the chloride penetration into concrete structures is more pronounced under combined attacks of chlorides, sulfates and carbonation. The diffusion coefficients and surface chloride contents were found to increase under combined multiple deterioration conditions. The present study provides quantitatively the penetration and diffusion characteristics of chloride ions in concrete structures under various deterioration conditions. The results of present study may be efficiently used for the realistic design of concrete structures under combined deterioration conditions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.623-631
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• 2018

In this study, the degree of deterioration of concrete was investigated in the laboratory under conditions of carbonation and freeze-thaw cycling, which are the major causes of the deterioration of its performance. In this test, the carbonated concrete was subjected to combined freeze-thaw deterioration tests for up to 300 cycles, and its dynamic elastic modulus and compressive strength were measured. The evaluation of the effect of the water-binder ratio on normal concrete subjected to combined carbonization and freezing-thawing showed that its resistibility against such combined deterioration decreased more rapidly in the concrete with a water-binder ratio of 55 % compared with that having a water-binder ratio of 35 %. In the case where the concrete was blended with a mineral admixture consisting of fly ash and blast furnace slag at the same water-binder ratio, it showed an increase of its resistibility against combined deterioration.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.625-628
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• 2008

This study is performed to evaluate the carbonation resistance by measuring carbonation penetration depth and diffusion equivalent air layer thickness for 3 types of repair materials and 2 types of surface protection materials. Diffusion equivalent air layer thickness($S_D$) is thickness of a static air layer that possesses, under the same conditions, the same carbon dioxide permeability as the coating in accordance BS EN 1062-6. There is a significant advantage that continuous test is possible because it does not destroy the specimen. From experiment results, it is concluded that determination of carbon dioxide permeability is effective to evaluate for surface coating materials.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.2
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• pp.165-182
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• 2006

In this study, field test was performed to investigate the strength-improvement effect of shotcrete mixed Micro-silica fume and shotcrete quality was estimated by EFNARC standard. Deterioration test combined the Freezing-thawing and Carbonation was also performed in order to investigate a long-term durability of high-strength shotcrete. As a result of test, the compressive strength of shotcrete using Micro-silica fume was 45.2~55.8MPa and flexible strength was 5.01~6.66MPa, so a promotion ratio of strength was 37~79%, 17~61% respectively. And the strength-improvement effect of strength by silica fume addition ratio of 7.5~10% for cement mass was more superior to the others. Due to relative dynamic modulus, mass decrease rate and carbonation progress of shotcrete mixed Micro-silica fume, it was especially realized that Micro-silica fume reduced deterioration caused by steel fiber and improved a long-term durability of shotcrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.3
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• pp.22-29
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• 2015

In this study, we tested to develop and apply structural insulation performance improvement concrete to field, which had compressive strength in 24 MPa and thermal conductivity twice as much as normal concrete. After experiment about slump and air contents, combination product of Plain and calcined diatomite powder showed reduction of slump and air contents and combination product with micro foam cell admixture, we cannot find result of slump and air contents reduction. Unit weight of combination product with insulation performance improvement materials decreased more than that of Plain. In the test of compressive strength, compressive strength of insulation performance improvement concrete decreased more than that of Plain but was content with 24 MPa. thermal conductivity of insulation performance improvement concrete tended to decrease. Freezing and thawing resistance of insulation performance improvement concrete was similar to that of Plain. In carbonation resistance test, combination product with calcined diatomite powder showed the result which was similar to that of Plain. In carbonation resistance test, combination product with micro foam cell admixture showed a increase compared to that of Plain and length variation of combination product generally increased.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.433-436
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• 2008

Deterioration in the concrete structure are due to carbonation, chloride ion attack and frost attack. Therefore, concrete structure is needed to surface protection for increase durability using silicate impregnants. Thus, this study is concerned with self-cleaning and durability of silicate hydrophilic impregnants of concrete structure using lithium and potassium silicates. From the experimental test results, lithium and potassium silicates have a good properties as a carbonation resistance. Lithium and potassium silicates make good use of hydrophilic impregnants of concrete structures.

• International Journal of Concrete Structures and Materials
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• v.9 no.3
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• pp.283-294
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• 2015

In the present study, a porous concrete with alkali activated slag (AAS) and coal bottom ash was developed and the effect of carbonation on the physical property, microstructural characteristic, and heavy metal leaching behavior of the porous concrete were investigated. Independent variables, such as the type of the alkali activator and binder, the amount of paste, and $CO_2$ concentration, were considered. The experimental test results showed that the measured void ratio and compressive strength of the carbonated porous concrete exceeded minimum level stated in ACI 522 for general porous concrete. A new quantitative TG analysis for evaluating $CO_2$ uptake in AAS was proposed, and the result showed that the $CO_2$ uptake in AAS paste was approximately twice as high as that in OPC paste. The leached concentrations of heavy metals from carbonated porous concrete were below the relevant environmental criteria.

• Advances in concrete construction
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• v.11 no.4
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• pp.307-314
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• 2021

Activated hwangtoh (ACT) is a natural resource abundant in South Korea, approximately 15.0% of soil. It is an efficient mineral admixture that has activated pozzolanic properties through high-temperature heating and rapid cooling. The purpose of this study is to improve a curb mixture that can reduce NOx outside and investigate durability performance. To this end, mortar curb specimens were manufactured by replacing OPC with ACT. The ACT substitution ratios of 0.0, 10.0, and 25.0% were considered, and mechanical and durability tests on the curb specimens were conducted at 28 and 91 days of age. Steam curing was carried out for three days for the production of curbs, which was very effective to strength development at early ages. The reduction in strength at early ages could be compensated through this process, and no significant performance degradation was evaluated in the tests on chloride attack, carbonation, and freezing and thawing. The mortar curb with an ACT of 10.0~25.0% replacement ratio exhibited clear NOx reduction through photocatalytic (TiO2) treatment. This is due to the increase in physical absorption through surface absorption and the photocatalyst-containing TiO2 coating. In this study, the reasonable range of the ACT replacement ratio for NOx reduction was quantitatively evaluated through a comprehensive analysis of each test.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.201-202
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• 2010

In this Study, we manufactured the 70, 100MPa grade high strength concrete with the land sand by batcher plant in the field. In order to verify attainment of design compressive strength and the durability of the manufactured concretes we examined the tests such as compressive strength test, freeze-thaw test, carbonation test, test for concrete's ability to resist chloride ion penetration.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.687-692
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• 2003

In this study, durability of concrete whose surface were treated by nano-composite hybrid polymer type coatings, which can provide a barrier against the ingress of moisture or aggressive ions to concrete, is discussed. For the durability evaluation of the coated concrete, chloride ponding test, accelerating carbonation test, porosity measurement test, and the SEM test are conducted. As the result of this study, it is found that nano-composite hybrid polymer type coated concrete has a much higher resistance to the ingress of chloride ion, carbon dioxide, moisture and aggressive acid than plain concrete has.