On self-healing of slag cement and alkali activated slag with CFBC bottom ash
- Issued Date
- 2021
- Abstract
- 순환 유동층 연소(Circular fluidized bed combustion, CFBC) 보일러는 석탄에서 전기를 생산하고 부산물로 CFBC 애시를 발생시킨다. CFBC 바텀애시를 일반 포틀랜드 시멘트 (Ordinary Portland cement, OPC)와 높은 비율로 혼합하면 바람직하지 않은 팽창과 열화가 발생한다. 이 연구는 다양한 폭의 균열 자체 치유를 위해 이러한 팽창성을 활용하는 것을 목표로 한다. CFBC 바텀애시의 다양한 치환률을 갖는 OPC 및 슬래그 시멘트 모르타르 시편을 제작하였다. 균열부의 투수성 및 디지털 현미경 이미지 처리 기술을 사용하여 자기치유의 속도와 정도를 평가했다. 주사 전자 현미경(SEM), 열 중량 분석(TGA) 및 X 선 회절(XRD)분석을 통해 균열부의 충진된 물질, 즉 치유물질의 미세 구조 및 구성에 대한 정보를 얻었다.
실험은 균열을 통해 유량과 균열 폭 사이의 관계, 서로 다른 결합재 시스템의 치유 속도, 서로 다른 균열폭을 가진 서로 다른 결합재에 대한 치유 후 균열부 투수성을 확인하였고, 이 때 서로 다른 방법의 치유 속도 측정 기술을 사용하였다. 실험 결과, CFBC 바텀애시를 서로 다른 기본 결합재에 혼입하면 모르타르의 균열 자기치유 특성이 향상되었음을 알 수 있었다. 또한 이 정도는 치유 전 샘플의 초기 균열 폭, 시편 자기 치유 시 환경 조건(탄산화 여부)에 크게 영향을 받는 다는 것을 확인하였다. |Circular fluidized bed combustion (CFBC) boiler generates electricity from coal and produces CFBC ashes as byproduct. CFBC bottom ash, when blended with ordinary portland cement(OPC) in high proportion, causes undesirable expansion and deterioration. This research aims on utilizing this expansive property for the self healing of cracks with various width. Samples were be prepared from OPC and slag cements with varying degree of replacement of CFBC bottom ash. Rate and degree of self healing were assessed by using permeability and digital microscope image processing techniques. scanning electron microscope (SEM), thermogravimetric analysis (TGA),and X-ray diffraction (XRD) tests were performed to provide further insight towards the microstructure and composition of the healing material.
The experiments were able to describe the relationship between flow through cracks and crack width, the rate of healing of different binders, the ultimate permeability after healing for different binders with different crack width, and compare different types of healing rate measuring techniques.
The results showed that the addition of CFBC ash to the different base binders improved the properties of self healing of the mortar specimen. Additionally, the crack widths of the samples before healing as well as the environmental condition before healing (presence of carbonation) had major implications on healing.
- Alternative Title
- CFBC 바텀애시를 혼입한 슬래그 시멘트 및 알칼리 활성 슬래그의 자기치유
- Alternative Author(s)
- Alemu Abel Shiferaw
- Affiliation
- Chosun University
- Department
- 일반대학원 건축공학과
- Advisor
- 김형기
- Awarded Date
- 2021-02
- Table Of Contents
- ABSTRACT ix
한글요약 xi
1 INTRODUCTION 1
1.1 Background 1
1.2 Research objective 2
1.3 Thesis layout 3
2 LITERATURE REVIEW 5
2.1 Introduction 5
2.2 Self-healing of cementitious materials 5
2.3 Hydration of cementitious binders 9
2.3.1 Hydration of ordinary portland cement 10
2.3.2 Hydration of alkali activated slag 11
2.3.3 Hydration of slag blended cement 12
2.4 Carbonation of cementitious binders 13
2.5 CFBC ash as a supplementary cementitious material 14
3 MEASUREMENT OF SELF HEALING RATE 16
3.1 Introduction. 16
3.2 Materials and mix 16
3.3 Crack generation and crack width control methods 19
3.4 Healing rate measurements 24
3.4.1 Permeability measurements 24
3.4.2 Optical microscopy measurements 27
3.5 Results and discussion 30
3.5.1 Relationship between flow and crack width 30
3.5.2 Crack width measurement-comparison between image processing and manual measurement techniques 32
3.5.3 Healing rate measurement by permeability 33
3.5.4 Healing rate measurement by image processing 38
3.6 Summary 41
4 HEALING MATERIAL CHARACTERIZATION 43
4.1 Introduction 43
4.2 Experimental program 43
4.2.1 Materials, mix design and sample preparation 43
4.2.2 XRF analysis 46
4.2.3 XRD analysis 47
4.2.4 Thermogravimetric analysis 49
4.2.5 Scanning electron microscope with Energy-dispersive X-ray spectroscopy 49
4.3 Results and discussion 50
4.4 Summary 56
5 CONCLUSION 58
5.1 Major findings 58
5.2 Limitations 59
5.3 Further study 60
6 APPENDIX 61
6.1 Appendix1:3D plots of all binders comparing permeability coefficient, crack width and healing duration 61
PUBLICATIONS 65
REFERENCES 66
ACKNOWLEDGEMENTS 79
- Degree
- Master
- Publisher
- Chosun University, Department of Architectural engineering
- Citation
- 알레무 아벨-쉬페로우. (2021). On self-healing of slag cement and alkali activated slag with CFBC bottom ash.
- Type
- Dissertation
- URI
- https://oak.chosun.ac.kr/handle/2020.oak/16846
http://chosun.dcollection.net/common/orgView/200000359230
- Appears in Collections:
- General Graduate School > 3. Theses(Master)
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