• Magazine of the Korea Concrete Institute
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• v.7 no.6
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• pp.224-232
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• 1995

Recently, in other.view of underwater concrete construction, special admixture agent of concrete has been developed for antiwashout of concrete under water with easy carrying out method in some foreign nations. They had successful cases in experiment and construction and it trend to use in many cases with many scales. However, in domestic, there was rare record in carrying out. In this paper, reference for successful results of experiment and construction about antiwashout underwater concrete, as variable add of special admixture agent and other agents. We have carried out property tests of fresh and hardened concrete, certified the properties and made the antiwashout underwater concrete have enough strength to endure with ea.sy construction. And we have decided the optimal mix proportion for antiwashout underwater concrete under standard state.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.345-346
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• 2010

The overall quality of underwater concrete will ultimately be affected by factors such as performance of antiwashout admixture and mix proportions of concrete. Of these, performance of antiwashout admixture may significantly influence quality of underwater concrete. Thus, objectives of this experimental research are to evaluate the performance such as slump flow, setting time, compressive strength, and water segregation of the concrete containing antiwashout admixture. It was observed from the test results that concrete containing antiwashout admixture was found to improve quality of concrete such as fluidity, compressive strength, and antiwashout compared to plain concrete.

• Magazine of the Korea Concrete Institute
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• v.8 no.5
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• pp.179-187
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• 1996

Many underwater concrete structures have been constructed recently in proportion to the increase of ocean developments. The research for the underwater concrete construction was mainly focused in view of placing method. Recently, special admixture agents of concrete were developed for antiwashout concrete under water in some foreign nations. They had successful results in experiments and site constructions. However. there are seldom experimental results or placements in domestic contry. In this paper. We had carried out property tests of fresh and hardened concrete with refer to successful results in experiments and site construction and investigated the physical variation of the antiwashout underwater concrete considering the interaction between antiwashout admixture and other ones. We have decided the optimal mix proportion fb;r antiwashout underwater concrete under standerd sea state.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3704-3712
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• 2012

Recently, antiwashout underwater concrete has been increasingly used for marine foundations of long span bridges. However, to shorten the construction period of antiwashout underwater concrete used in marine foundations, high fluidity antiwashout underwater concrete should be manufactured largely improving fluidity than the previous one. Thus, the objective of this experimental research is to suggest optimum mix proportions of high fluidity antiwashout underwater concrete. For this purpose, concrete specimens containing ground granulated blast furnace slag were manufactured according to the dosage of antiwashout admixture for unit binder contents of 550 and 600kg/$m^3$, respectively. And then, their quality performances such as slump flow, setting time, underwater segregation resistance, and ratio of compressive strength were evaluated according to the related specification of Korea Concrete Institute. It was observed from the test results that the minimum dosage of antiwashout admixture was necessary to satisfy the related specification.

• Journal of the Korean Ceramic Society
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• v.39 no.10
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• pp.963-969
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• 2002

In this studies, methly celluloes was used as antiwashout admixture and when considering the physical properties and economical efficiencies of Underwater Concrete as the results of making an experiencing slump flow, flow loss, setting time, suspension and pH also compressive strength and underwater/an air compressive strength ratio according to the adding amount changes 5, 7, 9, 11 kg/$m^3$ to Underwater Concrete of melamine superplasticizer, the using amount of melamine superplasticizer in Underwater Concrete approximately represents 9 kg/$m^3$.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.267-274
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• 2005

Preparation of cellulose type underwater non-segregation admixture was attempted and the hardening characteristics of underwater concrete according to the addition of this admixture was investigated in order to make underwater concrete with the compressive strength ratio of 0.8 to that of concrete manufactured in common atmosphere. The proposed underwater non-segregation admixture consisted of methyl cellulose of 0.4% by weight, silicon type antifoaming agent of 20% by weight, and sodium aluminate of 0.1% by weight to the amount of cement as setting accelerant, respectively. As the proposed non-segregation admixture was increased, the amount of suspended solid decreased, air content in concrete was increased but the flow loses by elapsed time did not change. The proper amount added of the proposed non-segregation adimixture was 0.8 wt% to the amount of cement. The compressive strength of the test sample underwater concrete manufactured by the addition of the proposed admixture was $325Kg/cm^3$, and the ratio of compressive strength of this sample concrete to that of a concrete manufactured in air was 0.94.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.6
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• pp.74-82
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• 1996

In this study, the characteristics of antiwashout underwater concrete according to the using types of admixture were experimentally investigated. Especially, the comparison on the performance of seven types(CO-A, B, C, D, E, F, G) of the manufactured admixtures was carried out in the same mixing condition and proportions. Based on the results of experiments, the conclusions were summarized as follows : (1) The slump flow on most of specimens except by CO-F type were progressed very well. (2) In most of products, the measured values of suspensions, pH's and air contents were lower than their reference values. However, CO-B, CO-F and CO-G types exceeded the reference ones in suspension and pH. (3) The time lags between initial and final setting were about three hours in most of tests, however, the maximum difference of total setting time was ten hours in comparing with the admixture types. The unit weights were mostly lower than $2300kg/m^3$ and the compressive strengths cured by salt water were about 80% of the ones by fresh water. (4) Finally, in spite of some problems, most of the manufactured admixtures may be performed well their functions in antiwashout under-water concrete if the using quantities are properly controlled by the site experiments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.57-62
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• 2020

Among the sewage pipes installed in Korea, the length of concrete pipes exceeding 20 years is 66,334 km (42.5%). Deteriorated concrete sewer pipes need to be repaired due to the leakage of internal sewage, which causes problems such as sink holes by expanding the cavity around the pipeline. In this study, we tried to apply anti-washout underwater mortar with ultra rapid hardening cement and segregation reducing agent to sewage pipe repair. As a result of the setting time test, the final set time was delayed by up to 172% by incorporating segregation reducing agent. In the test for measuring the degree of mortar segregation in water, it was measured at pH 12 or less under all mixing conditions. In addition, the suspension amount was measured to be 50 mg / l or less to satisfy the KCI-AD102 standard by incorporating a segregation reducing agent. In terms of the average value of mortar compressive strength, by incorporating segregation reducing agent, the strength of the specimens produced in air was more than 80% of that of the specimens produced in water. Conversely, the bond strengths of the specimens produced in water were measured to be higher than those of the specimens produced in air. Water resistance was evaluated by measuring water absorption and water permeability. Water absorption and water permeability were reduced by 42.6% and 36.6%, respectively, by mixing segregation reducing agent.

• Magazine of the Korea Concrete Institute
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• v.11 no.2
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• pp.231-239
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• 1999

When the concrete is cast at the sea, there are lots of restrictions in the working process being different from in land, and the concrete is suffered from the physical and chemical action in terms of marine environment. The compressive strength was measured after antiwash out underwater concrete mixed with fly ash had been cast and cured in order to produce the endurable high performance concrete, and then its characteristic was discussed by comparing one cured in air with in fresh water, and the effect of fly ash usage under the properly controled sea water temperature of $15{\pm}3^{\circ}C$ was also covered. The present work showed that the proper usage of fly ash was obtained at the condition of around 10% of substituted binder weight under the structure required the early age strength, and at the condition of over 40% if considering its durability and economy.

• Explosives and Blasting
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• v.38 no.4
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• pp.46-52
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• 2020

Although anti-washout grouts are used extensively in underwater targets, major constraints continue to be associated with their use. These include poor bonding strength, poor pumpability, and loss of high strength in everyday engineering applications. In this study, based on the literature pertaining to self-compacted, non-dispersive, anti-washout grouts, a review of research trends in anti-washout grouts for underwater construction and sealing of karst cavities was carried out in order to determine the problems faced in this field. Grouts used under water suffer a loss of strength and bonding strength in comparison to grouts cast in air. Researchers are designing high-viscosity grouts to overcome the inrush of water and seal karst cavities; however, in doing so, they have inadvertently caused serious problems pertaining to the pumpability of these grouts and concretes in deep target locations. Thus, the majority of the anti-washout grouts and concretes that have been developed are not applicable to deep target environments, instead being suitable for only near-surface targets.