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Park, Solmoi,Yoon, H.N.,Seo, Joonho,Lee, H.K.,Jang, Jeong Gook Elsevier 2020 Journal of hazardous materials Vol.387 No.-
<P><B>Abstract</B></P> <P>The structural evolution of a binder gel in alkali-activated cements exposed to accelerated leaching conditions is investigated for the first time. Samples incorporating fly ash and/or slag were synthesized and were exposed to electrically accelerated leaching by applying a current density of 5 A/m<SUP>2</SUP>. The leaching behavior of the samples greatly depended on the binder gel formed in the samples. The N-A-S-H type gel abundant in fly ash-rich samples showed some extent of dissolution upon accelerated leaching, while slag-rich samples underwent hydration of the anhydrous slag after leaching. The obtained results are discussed in view of the degradation of the binder gel induced by accelerated leaching, and their potential performance under repository conditions where groundwater-induced leaching is the main durability concern.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electrically accelerated leaching tests for alkali-activated materials are conducted for the first time. </LI> <LI> Fly ash samples show significant dissolution of binder gel upon leaching, unlike other samples. </LI> <LI> A low hydraulic property of fly ash prevents further hydration from occurring in contact with water. </LI> <LI> C-A-S-H type gel remains more stable in comparison with N-A-S-H type gel. </LI> <LI> Charge-balancing cations in alkali-activated materials have an important implication for the phase stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Thermodynamic Modeling of Long-Term Phase Development of Slag Cement in Seawater
Park, Solmoi(박솔뫼),Suh, Yongcheol(서용철),Nam, Kwang Hee(남광희),Won, Younsang(원윤상) 대한토목학회 2021 대한토목학회논문집 Vol.41 No.4
고로슬래그는 콘크리트의 염소이온침투 저항성능 개선 목적으로 가장 널리 활용되는 혼화재이나, 해수에 노출된 고로슬래그 혼입 콘크리트의 장기거동 및 상변이에 대한 보고는 부족한 실정이다. 본 연구에서는 열역학 모델링을 통해 해수에 노출된 슬래그 시멘트의 장기 상변이를 모사하였다. 모델링 결과 슬래그 혼입은 해수에 노출되었을 때 상변이가 쉽게 일어나지 않는 안정적인 상을 생성시킬 것으로 예측되었다. 해수에 노출되었을 때 ettringite 생성으로 인해 포틀랜드 시멘트 및 슬래그 시멘트에서 모두 팽창이 일어날 것으로 예측되었으나, 슬래그 시멘트에서는 brucite가 덜 생기는 것을 확인하였다. 공극률은 슬래그 혼입 시멘트의 경우 더 높았으나, 염소 흡착능이 높은 알루미네이트 수화물이 슬래그 시멘트에서 더 활발히 생성되는 것을 확인하였다. 따라서 슬래그 혼입을 통해 해양 환경에서 사용되는 콘크리트의 내구성능을 크게 증진시킬 수 있는 것으로 나타났다. Known to improve resistance to chloride ingress, blast furnace slag is a widely used supplementary cementitious material. However, a detailed characterization of cements blended with slag exposed to seawater remains unavailable. This study employs thermodynamic modeling as a toolkit for assessing the long-term phase evolution of slag cement in seawater. The modeling result shows that slag incorporation leads to the formation of phases that are less prone to structural alteration in seawater. Formation of more ettringite is expected to induce expansion in both plain and blended cements, while brucite is unstable in the blended systems. Despite this, the porosity is expected to increase in the blended cements, and aluminate hydrates with a higher chloride binding capacity are more abundant in the blended cements. The results suggest that the use of slag in concrete improves the durability performance of concrete in marine environments.
열역학 모델링을 활용한 SCM의 반응도 예측에 관한 연구
다니엘타리쿠 ( Daniel Tariku ),박솔뫼 ( Solmoi Park ) 한국구조물진단유지관리공학회 2023 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.27 No.1
The materials investigated in this study are cement blended with fly ash and slag. For measurement of reactivity, the procedure in this study involves measuring the bound water content of hydrated blended samples using TGA and determining at which specific amount of SCM we can get bound water content from thermodynamic modelling that is similar to measurements from TGA. This technique is relatively simple and straightforward than the conventional methods available to estimate reactivity of SCMs and its predictions are shown to be fairly close to reactivity measurements from selective dissolution.
Effect of CaSO<sub>4</sub> on hydration and phase conversion of calcium aluminate cement
Son, H.M.,Park, Solmoi,Kim, H.Y.,Seo, J.H.,Lee, H.K. Elsevier 2019 Construction and Building Materials Vol.224 No.-
<P><B>Abstract</B></P> <P>Conversion from metastable phase to stable phase in calcium aluminate cement (CAC) causes volumetric instability, resulting in loss of compressive strength. This study investigated the effect of CaSO<SUB>4</SUB> on the phase conversion of calcium aluminate cement. The specimens with different dosage of CaSO<SUB>4</SUB> were exposed to 60 °C to trigger the phase conversion of CAC after curing at 20 °C for 7 days. Analysis with X-ray diffraction, thermogravimetry, mercury intrusion porosimetry, and scanning electron microscopy were conducted. The incorporation of CaSO<SUB>4</SUB> inhibited the formation of unstable CAH<SUB>10</SUB> by direct precipitation of ettringite. As a result, the reduction of strength of CAC specimens due to the increased pore volume by conversion was inhibited by ettringite and monosulfate formation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CaSO<SUB>4</SUB> had influenced on hydration and conversion of calcium aluminate cement (CAC). </LI> <LI> The reduction of strength of CAC specimens was inhibited. </LI> <LI> The incorporating of CaSO<SUB>4</SUB> inhibited the formation of unstable CAH<SUB>10</SUB> by direct precipitation of ettringite. </LI> </UL> </P>
NaOH-활성 플라이애시/슬래그의 반응생성물에 기여하는 플라이애시의 역할
카마사니치란지비레디 ( Kamasani Chiranjeevi Reddy ),박솔뫼 ( Park Solmoi ) 한국구조물진단유지관리공학회 2021 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.25 No.2
The role of fly ash in fly ash/slag blends activated with 1, 3, and 6M NaOH solution is investigated. The compressive strength decreased with an increase of fly ash content in the binder material. C-(A)-S-H is identified as the prominent reaction product. The dissolved Si from fly ash modified C-(A)-S-H structure by incorporating silica into C-(A)-S-H. The silica incorporation increased with an increase in activator molarity and resulted in enhanced strength.