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Effect of Nano-SiO2 and MgO on the properties of non-dispersible underwater concrete

Title
Effect of Nano-SiO2 and MgO on the properties of non-dispersible underwater concrete
Other Titles
나노실리카와 산화마그네슘이 수중 불분리 콘크리트의 특성에 미치는 영향
Author
전인규
Alternative Author(s)
전인규
Advisor(s)
유재석
Issue Date
2021. 2
Publisher
한양대학교
Degree
Master
Abstract
The underwater concrete (UWC) was widely used in construction site. However, even though using anti-washout admixtures (AWAs) and viscosity-modifying admixtures (VMAs), UWC has a problems in actual construction site, such as segregation, water pollution due to cement washout, and low workability. In addition, UWC in marine environment induce significant degradation of durability due to free chloride ion in the seawater. The researchers studied several supplementary (SCM) cementitious materials to increase the flowability and durability of UWC. In this study, Nano-SiO2 was used as an additive material, and MgO was used as a replacement of cement binder. The fresh properties of UWC mixes was assessed in terms of slump flow and anti-washout measurement. It verified that the Nano-SiO2 and MgO has slightly negative effect to workability, but both Nano-SiO2 and MgO has a positive effect to increase the anti-washout resistance through reducing the pH value and turbidity results. It is also revealed that mechanical properties are increased with addition of Nano-SiO2 and decreased with MgO replacement. The hydration, microstructure and durability performance was investigated in terms of isothermal calorimetry, mercury intrusion porosimetry, thermogravimetric analysis, x-ray diffraction analysis, scanning electron microscopy, carbonation, and chloride penetration test. The results indicated that Nano-SiO2 can enhance the hydration degree and pozzolanic activity to produce extra C-S-H gel to densify the microstructure of UWC concrete mixes, while MgO has slightly decrease the hydration reaction and produce Mg combined hydrotalcite phase in hydration process. Both Nano-SiO2 and MgO has positive effect to increase the durability performance through reduce the porosity, but incorporating MgO revealed higher effectiveness on chloride resistance compared to Nano-SiO2 addition.
URI
https://repository.hanyang.ac.kr/handle/20.500.11754/159827http://hanyang.dcollection.net/common/orgView/200000485491
Appears in Collections:
GRADUATE SCHOOL[S](대학원) > CIVIL AND ENVIRONMENTAL ENGINEERING(건설환경공학과) > Theses (Master)
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