• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.1
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• pp.173-179
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• 2003

Currently, in the mix design of high strength concrete, cement content depend on the target slump which is fixed with tests. However this cause high content cement use because it is based on the mix design of normal strength concrete. Also, comparatively high content cement might decrease the durability of the concrete. Therefore, in this study, we investigated proper cement content satisfying durability, workability, compressive strength, and reviewed use of admixtures, proper sand-aggregate ratio to the cement content. The results indicate that cement content ranging $370{\sim}550kg/m^3$ did not affect the compressive strength. The field workers should consider durability, workability as well as compressive strength for determining the optimal cement content in the mix design of the high strength concrete.

• 한국도로학회:학술대회논문집
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• 2008.10a
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• pp.193-197
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• 2008

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.249-256
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• 2008

The durability of marine concrete structure is severely degraded by corrosion due to penetration and diffusion of chloride. So, many researches have been performed to improve the durability in marine concrete structure. In this study, the concrete members mixed with the mineral admixtures(SF and BFS), the epoxy-coated steel, and corrosion inhibitors are prepared, and four-point bending test of specimens are performed to investigate the flexural behaviors and the applicability for marine concrete structure. From the test results, the mineral admixtures and inhibitors are useful for safety against the initial cracking and the bending resistance in specimens. When the durable material is used in specimen, the tensile stress of reinforcing rod was less variable in same bending span length, and the durable member showed a stable behavior. And it is evaluated that the crack spacing is not larger in specimen used the durable material.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.185-186
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• 2010

For Mega foundation, concrete must have high strength and high flowability. Especially in marine environment, concrete durability becomes a significant property. In this study, high durable concrete, under marine environment, was developed. And to estimate its performance, the world's biggest Mock Up test, $4m{\times}4m{\times}4m$ size, was performed.

• International Journal of Highway Engineering
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• v.11 no.3
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• pp.41-49
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• 2009

Cement concrete pavement has become more common in Korean highway systems. However, as its service period increases, there are some technical problems occurs and no clear solution is available primarily due to the lack of active researches. This research, hence, aims to develop a new mix proportion that may provide better strength and durability with extended service life. Based on a variety of literature reviews, the experimental variables were determined as unit cement content, S/a ratio and W/C ratio. From the experimental works, it is recommended to increase the unit cement content up to 375kg/$m^3$, 400kg/$m^3$ and 425kg/$m^3$. The target slump and air content were set 40mm and 5%, respectively. The maximum size of coarse aggregate was decided to be 25mm because of the easiness of supply in the field. The reduction of W/C ratio was necessarily required and decreased to 0.4 which was proven not to cause any mixing problem with the increased unit cement contents along with polycarbon-based high range water reducing agent. In addition, it was known that the S/a ratio could be reduced to 0.34. The lowered S/a might be possible because of the increased cement paste and hence increased cohesiveness and workability.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2A
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• pp.171-179
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• 2009

The porosity in porous media like concrete can be considered as a durability index since it may be a routine for the intrusion of harmful ions and room for the keeping moisture. Recently, modeling and analysis techniques for deterioration are provided based on the pore structure with the significance of durability and the relationship between porosity and durability characteristics is an important issue. In this paper, a series of mortar samples with five water to cement ratios are prepared and tests for durability performance are carried out including porosity measurement. The durability test covers those for compressive strength, air permeability, chloride diffusion coefficient, absorption, and moisture diffusion coefficient. They are compared with water to cement ratios and porosity. From the normalized data, when porosity increases to 1.45 times, air permeability, chloride diffusion coefficient, absorption, and moisture diffusion coefficient decrease to 2.3 times, 2.1 times, 5.5 times and 3.7 times, respectively, while compressive strength decreases to 0.6 times. It was evaluated that these are linearly changed with porosity showing high corelation factors. Additionally, intended durability performances are established from the test results and literature studies and a porosity for durable concrete is proposed based on them.

• Cement Symposium
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• s.33
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• pp.109-114
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• 2006

• 한국도로학회:학술대회논문집
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• 2006.03a
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• pp.137-144
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• 2006

• Magazine of the Korea Concrete Institute
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• v.24 no.2
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• pp.37-42
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• 2012

• Computational Structural Engineering
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• v.23 no.5
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• pp.23-33
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• 2010