Evaluation and Improvement of Performance of Concrete Containing Coal Bottom Ash and Reclaimed Asphalt Pavement Aggregate as 100% Aggregate Replacement
석탄저회 및 재생 아스팔트 골재를 이용한 100% 골재 치환 콘크리트의 성능평가 및 개선
- 주제(키워드) 도움말 Concrete , Waste recycling , Coal Bottom Ash , Reclaimed Asphalt Pavement Aggregate , Roller compacted concrete , Sustainable construction
- 발행기관 강릉원주대학교 일반대학원
- 지도교수 도움말 이승우
- 발행년도 2024
- 학위수여년월 2024. 8
- 학위명 석사
- 학과 및 전공 도움말 일반대학원 토목공학과
- 세부분야 해당없음
- 실제URI http://www.dcollection.net/handler/kangnung/000000011790
- UCI I804:42001-000000011790
- 본문언어 영어
초록/요약 도움말
지속 가능한 건설을 위해서는 천연 골재 생산과 폐기물 처리로 인해 발생하는 환경적인 영향에 대응할 필요가 있다. 이에 따라 신뢰성, 경제성, 친환경성 및 풍부하게 사용 가능한 조건을 충족하는 대체 골재의 탐색이 요구된다. 글로벌하게 이용 가능하고, 경제적이며 천연 골재와 유사한 특성을 가진 Coal Bottom Ash (CBA) 및 Reclaimed Asphalt Pavement Aggregate (RAPA)은 주로 매립지에 처분되고 있다. 따라서 본 연구에서는 콘크리트 포장에서 잔 골재와 굵은 골재를 각각 완전히 대체하기 위해 CBA 와 RAPA 의 사용 가능성을 탐구하였다. CBA-RAPA 콘크리트 시편을 제작하여 시험을 실시한 결과 건조 수축과 기포 간격 계수 모두 만족스러운 성능을 나타냈다. 콘크리트의 강도 시험 결과에서 휨 인장 강도는 기준치 이상을 달성하였으나, 압축 및 쪼갬 인장 강도는 예측된 것보다 낮은 것으로 나타났다. 28 일 휨 인장 강도를 기준으로는 권장 설계 기준을 충족하지만, 콘크리트 팽창 현상과 같은 압축 파괴의 경우 낮은 압축 강도에 의해 문제가 발생한다. 또한 재령 3 일 이후에 측정된 CBA-RAPA 콘크리트의 압축강도 및 인장강도는 천연골재콘크리트(NAC)에 비해 낮은 증가율이 확인되었다. CBA-RAPA 콘크리트와 NAC 의 강도 및 강도 발달의 차이점은 RAPA 의 특성인 약한 골재의 응집력과 오래된 아스팔트 코팅으로 인해 발생하는 과도한 interfacial transition zone(ITZ)를 통해 설명할 수 있다. ITZ 는 Backscattered Electron 및 Scanning Electron Microcopy 분석을 통해 확인되었으며, RAPA 콘크리트의 경우, 골재의 다공성과 NAC 에 비해 큰 ITZ 로 인해 수화반응이 감소하여 강도가 저하된다. 이에 따라 롤러 다짐 콘크리트에서 사용되는 다짐 방법과, 배합 전 RAPA 를 콘크리트 믹서를 통해 마모시키는 두 가지 방법을 사용하여 낮은 강도 거동을 향상 시켰다. 다짐 방법은 골재의 맞물림을 향상시키며, RAPA 의 마모 방법은 골재가 응집되어 있는 것을 파괴하고 아스팔트 코팅을 부분적으로 제거하여 RAPA 의 단점을 최소화 하였다. 이러한 처리는 압축 강도와 휨 및 쪼갬 인장 강도를 향상시켰으며, 이는 RAPA 마모와 다짐 방법의 결합에 의한 효과로 판단된다. 실험 결과 CBA-RAPA 콘크리트는 NAC 와 유사한 강도 거동을 나타냈으며, 적절한 처리를 통해 CBA 및 RAPA 를 활용하는 것이 가능할 것으로 판단된다. 이는 탄소 배출량을 줄이고 폐기물 관리를 개선하며, 천연 자원을 보존하는 것이 지속 가능한 건설에 기여할 수 있음을 의미한다.
more초록/요약 도움말
Efforts toward sustainable construction practices necessitate addressing the environmental impact associated with the production of natural aggregates and the disposal of waste in landfills. Thus, several highway authorities have been compelled to explore alternative sources of aggregates that are reliable, economical, eco-friendly, and abundantly available. Despite their global availability, cost-effectiveness, and properties comparable to natural aggregates, Coal Bottom Ash (CBA) and Reclaimed Asphalt Pavement Aggregate (RAPA) mostly end up in landfills. Therefore, this study explores the potential of utilizing CBA and RAPA as complete replacements for fine and coarse aggregates, respectively, in concrete pavements. Specimens were produced, and laboratory tests were conducted, revealing satisfactory performance in drying shrinkage and air void parameters. Despite achieving satisfactory flexural strength, the concrete exhibited lower compressive and splitting tensile strengths than predicted. Furthermore, the strength behavior of CBA-RAPA concrete was observed to deviate from that of natural aggregate concrete (NAC), primarily due to the low rate of increase in compressive and tensile strengths observed after 3 days. While meeting the recommended design criteria based on 28-day flexural strength, the low compressive strength may pose challenges in cases of compressive stress failures, such as the concrete blow-up phenomenon. The lower strength and deviation in strength development behavior from NAC were attributed to weak agglomerated aggregates in RAPA, the large and porous interfacial transition zone (ITZ), and the lower concentration of hydration products at this zone, due to the old asphalt coating surrounding RAPA, as confirmed by Backscattered Electron and Scanning Electron Microscopy analyses of the ITZ. To enhance the strength behavior, two methods were employed: compaction using roller-compacted concrete fabrication method, and RAPA abrasion, carried out by rolling RAPA in a concrete mixer before mixing. Compaction improved aggregate interlock, while RAPA abrasion decreased agglomerated aggregates and partially removed the asphalt coating, thereby reducing its adverse effects. These treatments resulted in improvements in compressive, flexural, and splitting tensile strengths, with the combined effect of both treatments being the most significant. Results indicated that CBA-RAPA concrete exhibited behavior more similar to NAC after the treatments. This research suggests that, with appropriate treatments, the utilization of CBA and RAPA in concrete is feasible in the future, potentially contributing to sustainable construction practices by reducing carbon footprints, improving waste management, and conserving natural resources.
more목차 도움말
TABLE OF CONTENT
국문 요약 ..................................................................................................................... i
ABSTRACT ............................................................................................................. iii TABLE OF CONTENT ............................................................................................ v LIST OF TABLES ................................................................................................. viii LIST OF FIGURES ................................................................................................... x LIST OF ACRONYMS AND SYMBOLS ............................................................ xii CHAPTER 1: INTRODUCTION ............................................................................ 1
1.1 Background of the Study ............................................................................. 1
1.2 Purpose of Study ......................................................................................... 4
1.3 Scope ........................................................................................................... 5
1.4 Dissertation Outline .................................................................................... 5
CHAPTER 2: SELECTION OF RECYCLED AGGREGATES .......................... 7
2.1 Considered Recycled Aggregates................................................................ 7
2.2 Factors Considered ...................................................................................... 8
2.3 Selection Survey.......................................................................................... 8
2.4 Analysis and Selection .............................................................................. 10
CHAPTER 3: LITERATURE REVIEW .............................................................. 16
3.1 Life Cycle Assessment (LCA) .................................................................. 16
3.2 Properties and Uses of CBA ..................................................................... 18
3.2.1 Physical Properties of CBA ............................................................... 18
3.2.2 Chemical Properties of CBA ............................................................. 20
3.3 CBA as Fine Aggregate Replacement in Concrete ................................... 22
3.4 Properties and Uses of RAPA ................................................................... 24
3.4.1 Physical Properties of RAPA ............................................................ 24
3.4.2 Chemical Properties of RAPA ........................................................... 26
3.5 RAPA as Coarse Aggregate Replacement in Concrete ............................. 26
CHAPTER 4: PROPERTIES OF 100% CBA-RAPA CONCRETE .................. 30
4.1 Introduction ............................................................................................... 30
4.2 Life Cycle Assessment .............................................................................. 31
4.2.1 Goal and scope definition .................................................................. 31
4.2.2 Life Cycle Inventory (LCI) ................................................................ 33
4.2.3 Life Cycle Impact Assessment (LCIA) ............................................. 33
4.2.4 Interpretation of results ...................................................................... 35
4.3 Materials Collection and Evaluation ......................................................... 37
4.4 Mix Proportioning ..................................................................................... 40
4.5 Methodologies ........................................................................................... 40
4.5.1 Fresh Concrete Properties .................................................................. 40
4.5.2 Compressive Strength ........................................................................ 41
4.5.3 Flexural Strength ............................................................................... 42
4.5.4 Splitting Tensile Strength .................................................................. 43
4.5.5 Backscattered Electron and Scanning Electron Microscopy ............. 44
4.5.6 Drying Shrinkage ............................................................................... 45
4.5.7 Microscopic Determination of Air Void Parameters ......................... 46
4.6 Results and Discussions ............................................................................ 46
4.6.1 Compressive Strength ........................................................................ 46
4.6.2 Flexural Strength ............................................................................... 51
4.6.3 Splitting Tensile Strength .................................................................. 53
4.6.4 Backscattered Electron and Scanning Electron Microscopy ............. 55
4.6.5 Comparison of strength behavior to natural aggregate concrete ....... 56
4.6.6 Drying Shrinkage ............................................................................... 62
4.6.7 Microscopic Determination of Air Void Parameters ......................... 63
CHAPTER 5: IMPROVEMENT OF STRENGTH BEHAVIOR OF CBARAPA CONCRETE ................................................................................ 65
5.1 Strategy to improve strength behavior ...................................................... 65
5.1.1 RAPA Abrasion ................................................................................. 67
5.1.2 Roller Compacted Concrete (RCC) ................................................... 67
5.2 Test Setup .................................................................................................. 68
5.2.1 RAPA Abrasion Setup ....................................................................... 68
5.2.2 Vebe consistency test......................................................................... 72
5.2.3 Mix proportioning ............................................................................. 73
5.2.4 Strength Test Methodologies ............................................................. 77
5.3 Effect of RAPA Abrasion on Strength Behavior ...................................... 77
5.4 Effect of Compaction on Strength Behavior ............................................. 80
5.5 Combined Effect of RAPA Abrasion and Compaction ............................. 83
5.6 General Comparison of Strength Results .................................................. 85
CHAPTER 6: SUMMARY AND CONCLUSION ............................................... 90
6.1 Summary ................................................................................................... 90
6.2 Conclusions ............................................................................................... 90
6.3 Recommendations for Future Studies ....................................................... 92
REFERENCES ........................................................................................................ 94
APPENDIX A ........................................................................................................ 103
APPENDIX B ......................................................................................................... 108
APPENDIX C ........................................................................................................ 112
