• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.5
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• pp.106-114
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• 2006

This paper investigates the fundamental properties and shrinkage characteristics of low shrinkage high performance concrete(LSHPC), using mock-up specimens. According to the test results, the most suitable mix proportions of LSHPC need a higher dosage of SP agent and AE agent, in order to obtain the target of slump flow and air content. This is due to reduce fluidity and air content respectively. It also presented earlier setting time than control concrete by 6 hours and exhibited compressive strength of 60MPa at age 28 days. Autogenous shrinkage of LSHPC was the half of the value of control concrete. Drying shrinkage of center section of LSHPC showed similar tendency with autogenous shrinkage, because of no internal moisture movement, while surface section had larger drying shrinkage. The specimen with embedded reinforcing bar had smaller deformation owing to confinement of reinforcing bar.

• Journal of the Korea Institute of Building Construction
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• v.14 no.3
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• pp.223-229
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• 2014

In this study, the fire resistance of high strength concrete with organic fibers and polymer powder (PW) was investigated. Two types of the specimens of ${\phi}100{\times}200mm$ and $300{\times}300{\times}600mm$ sizes were prepared. As a result of the test, it was found that the fiber-to-PW mixing ratio of 1:1 achieved the highest fluidity. Further, it was found that the mixing ratios of PP 0.05% + PW 0.05%, PNY 0.05% + PW 0.05% was sufficient to protect the high strength concrete from spalling. For the mock-up specimens of $300{\times}300{\times}600mm$ size, if the required amounts of fibers were added in the concrete. the concrete spalling was resisted. Likewise, in the case of the polymix (PM) together with PW, all the tested specimens were satisfactory for fire resistance performance.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.609-612
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• 2008

Ultra Super Early Strength Cement is a material that satisfies these requirements. early hydration heat however, is significant over regular concrete, thus discretion is advised for thermal cracks in accordance with heat generation when constructing a large-scale structures. In addition, the negative point that it is difficult to achieve required strength in a short period of time following rubbing process while retaining workability, the cement is being used conditionally for engineering material and Ultra Super Early Strength Cement for maintenance material for construction doesn't exist. Magnesia Phosphate Cement, which is currently under studies in overseas uses no extra admixture and has strong points of Ultra Super Early Strength as well as favorable construction-ability and adhesive stability to the prototype concrete. These factors stem recognition that it could be used as maintenance material for construction of diverse applicability. In order to provide necessary data to increase practicality of the magnesia phosphate cement for Ultra Super Early Strength Mortar, the study carried out simulate experiment on member of framework to review field applicability.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.161-168
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• 2008

The freeze-thaw deterioration and chloride attack, which are the typical degradation factors for durability of marine concrete, are significantly affected by pore structures in terms of penetration and diffusion. These pore structures of concrete are closely related to the types and amount of AE agent, used to guarantee the resistance of freeze-thaw deterioration, and the elapsed time before concrete pouring. This paper evaluates the durability of concrete based on the results of tests on cylinder specimens and core specimens from mock-up members with different air content of 4~6% and 8~10%, respectively. According to the test results, the air content of hardened concrete is 2.5~5.2% at 7 days and 2.4~5.1% at 28 days. These air contents are about half of the initial values just after the concrete mixing. Judging from the amount of scale after the freeze-thaw test completed, air content of 8~10% is slightly more beneficial against the deterioration of concrete than air content of 4~6%. Meanwhile, the core specimens from mock-up members exhibit somewhat unfavorable freeze-thaw deterioration and chloride migration characteristic compared with the cylinder specimens tested in the laboratory under the same mixing condition, as to show 106% in freeze-thaw test and 160% in chloride diffusion coefficient test, respectively.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.6 s.58
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• pp.88-96
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• 2009

In this Study, FR-ECC(Fire Resistance Engineered Cementitious Composites) in which at same time it can improve the endurance and fire-resistance efficiency of a Structure was developed, and the experimental study such as thermal characteristic, Fire-resistance efficiency, and etc was performed for using FR-ECC as the repair materials for building and civil Structure. Moreover, it was evaluated about the field applicability of FR-ECC. As a result, FR-ECC is superior to the existence fire resistance repair mortar in strength and durability property. Also, FR-ECC was exposed to have the characteristic of being excellent than existence fire resistance mortar in the field applicability.