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7. Hydration Characteristics of Slag-Ca(OH)2-Al2O3 Binder in a 60 °C Curing Environment with Brine as Mixing Water.

Author

Kang, Choonghyun, Kim, Taewan, Park, Yong-Myung, and Seo, Ki-Young

Subjects
REVERSE osmosis in saline water conversion, SALT, SEAWATER composition, REVERSE osmosis, SLAG cement, SALINE water conversion
Abstract

Recently, research results on PC-based or alkali-activated slag cement (AASC) using seawater as mixing water have been reported. Unlike seawater, reverse osmosis brine (brine) is waste discharged into the ocean from seawater desalination plants. There is a need to develop new and effective methods of disposing or utilizing brine to reduce marine pollution, protect marine ecosystems, and increase marine plant construction. However, research on cement or concrete using brine as a mixing water is very limited. Brine has almost the same composition as seawater, and the ion concentration is 2–4 times higher. Therefore, it is believed that new methods of using brine can be investigated and developed based on existing research and experimental results on seawater. The effects of brine and aluminum oxide (AO) on activated slag with calcium hydroxide (CH) were investigated for hydration and mechanical properties. 5% and 10% of CH were used, and samples using fresh water (FC) were prepared at the same time for comparison with brine. The slag sample without CH has a low initial (1 and 3d) strength of about 10 MPa for both FC and brine, but increases rapidly from 7d. Incorporation of CH was effective in improving the mechanical performance of FC and brine samples. In addition, the brine sample exhibited higher strength than the FC sample because it formed fewer C3AH6 phases that cause volume instability than the FC sample and affected the hydration promotion of slag particles. And more calcite phases were observed in the brine samples than in the FC samples. Through this study, the possibility of using brine as a building material was confirmed. In addition, the effect of chloride ion adsorption of slag mixed with AO and CH on the physical properties and mechanical performance of the hydration reaction was confirmed. [ABSTRACT FROM AUTHOR]

Published
2024
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26. Recovery of Protective Performance of Cracked Ultra High Performance-Strain Hardening Cementitious Composites (UHP-SHCC) Due to Autogenous Healing

Author

Minoru Kunieda, Kang Choonghyun, Naoshi Ueda, and Hikaru Nakamura

Subjects
Cracking, Materials science, Silica fume, Air permeability specific surface, Ultimate tensile strength, Pozzolanic reaction, Hardening (metallurgy), General Materials Science, Building and Construction, Permeation, Strain hardening exponent, Composite material
Abstract

A new strain hardening cementitious composite with a dense matrix, Ultra High Performance-Strain Hardening Cementitious Composites (UHP-SHCC), has been developed. This material combines excellent protective performance with a significantly higher tensile strength and strain hardening at tensile strength. Further, the material has controlled fine cracks (less than 30 microns). A low water to binder ratio with silica fume that causes a pozzolanic reaction is used in UHP-SHCC. These characteristic may give advantages for autogenous healing after the cracking. This paper presents autogenous healing behavior of cracked UHP-SHCC, and discusses about recovery of protective performance through air and water permeability test results. It was confirmed that UHP-SHCC has potentially autogenous healing properties. The air permeability coefficient and water permeation were dramatically decreased by increasing of re-curing period. Re-curing in water was more effective than re-curing in air for recovery. The effect of induced damage level on recovery of the used indices was not significant, because crack width was controlled and was almost the same among all the cracks. The repeatability of autogenous healing (twice in this study) was confirmed.

Published
2012

27. AUTOGENOUS HEALING PROPERTIES OF CONCRETE UNDER FLEXURAL LOADING

Author

KANG, Choonghyun, KUNIEDA, Minoru, UEDA, Naoshi, and NAKAMURA, Hikaru

Subjects
cement based material, autogenous healing, crack, initial loading age, bending test
Abstract

Autogenous healing of concrete structure was studied as a part of measures for reduction of the total life cycle cost. This study presents the measurement for autogenous healing ability by using the stiffness through three-point bending test. It shows the relation between autogenous healing ability and the initial loading age for three kinds of concrete, such as normal concrete, fly ash concrete and fly ash concrete with fiber. Furthermore, the size effect of specimens on autogenous healing is examined.

Published
2011

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