• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.44-49
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• 2019

The purpose of this study is to analyze the fundamental characteristics of concrete with the change of reject ash(Reject ash=Rj) in the mixed aggregate where single grain aggregate of different grain size and aggregate of opposite grain size are mixed together, to analyze the possibility of a mixed aggregate system that premixes at an aggregate manufacturing plant and delivers it as one aggregate. As a result of the experimental study, it was found that the grain size regulation is satisfied if the mixed aggregate(CSb+SS) is substituted for about 5% of Rj. In the case of the fluidity slump, slump flow and air volume, it was found that they decrease as the substitution ratio of Rj increases, while the compressive strength increases as the substitution ratio of Rj increases. Therefore, it is analyzed that it would contribute greatly to an improvement of quality such as improvement of compressive strength if adequate fluidity and air quantity are secured by the water reducing agent and AE agent while premixing the Rj, which is disposed of by landfill, with about 5% of the mixed aggregate.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.765-768
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• 2008

The prevent methods of Alkali-Silica Reaction (ASR) are studying after the failure cases by ASR were reported in Korea. When ASR failure is causing to the step of maintenance, the available repair methods were rarely studied in the World. In this study, premixed fly ash cement was applied to prevent ASR in the concrete pavement. The ratio of fly ash and cement is 20 percent and 80 percent by weight of total cementious material. The construction performance of premixed fly ash cementious concrete pavement was studied that the application is verify to performance collected data during the constructing in the field. The freeze-thaw test was studied to verify durability of the premixed fly ash cementious material made specimen in the laboratory. The results show that construction performance and durability are well condition in this test section and freeze-thaw test.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.247-252
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• 2017

The aim of this research is the feasibility analysis of the reject ash premixed cement mortar with combined aggregate. Namely, for the combined aggregate with two different qualities of aggregates, a fundamental properties of cement mortar was evaluated depending on various replacing ratios of reject ash(Ri). According to the experimental results, the combined aggregate consisted with low-quality aggregate and sea sand did not change the flow value depending on the reject ash while the combined aggregates consisted with low quality aggregate and sea sand; and consisted exploded debris sand and sea sand the increasing reject ash increased the air content with increased replacing ratio of reject ash. In the case of compressive strength, as the replacing ratio of reject ash was increased, the compressive strength was increased. It is considered that when 5% of reject ash replacing ratio made similar quality of cement mortar with favorable quality aggregate, hence, it can be suggested that 5% replacement of reject ash for desirable fluidity and compressive strength of concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.261-262
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• 2009

The prevent methods of Alkali-Silica Reaction (ASR) are studying after the failure cases by ASR were reported in Korea. In this study, the freeze-thaw test and scaling test for premixed fly ash cement were performed. The ratio of fly ash and cement is 20 percent and 80 percent by weight of total cementious material. The results show that the dynamic modulus after 300 cycles the freeze-thaw test for most of specimen except the specimen have less 3% air was more than 90 % and the loss of weigh the specimen after 50 cycles scaling test was less than 1kg/$m^3$.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.365-368
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• 2008

This research is related to 240MPa ultra-high strength concrete(UHSC) with extremely loss W/B ratio. For this development, High flow cement is mainly used which has a short reaction rate due to the high blaine and high early strength, which can make greater fluidity in case of very low W/C ratio. It made the best mixture using the mineral admixtures silica fume, slag powder and special admixture. For dispersibility and homogeneity of cement binder, cement of premix type is produced using omni-mixer. Moreover, it ensures the fluidity of ultra-high strength concrete(UHSC). For having a good fire performance, we made an experiment special coarse aggregate. As a result, we got 180MPa in case of water curing, 200MPa in case of steam curing and uniform UHSC of 240MPa in case of a special curing method.