탄산화 공정과 계면활성제의 상호작용에 따른 시멘트 페이스트의 탄산화 효율 및 역학적 특성 분석 = Analysis of the Carbonation Efficiency and Mechanical Properties of Cement Paste as Influenced by the Interaction Between the Carbonation Processes and Surfactants

다국어 초록 (Multilingual Abstract)

Analysis of the Carbonation Efficiency and Mechanical Properties of Cement Paste as Influenced by the Interaction Between the Carbonation Processes and Surfactants Jeonguk Mun Advisor : Prof. Heeyoung Lee, Ph.D. Department of Civil Engineering Graduate School of Chosun University Mineral carbonation of cementitious materials has been studied as a carbon capture, utilization, and storage strategy. Surfactants can modify gas–liquid–solid interfaces and improve CO2 transport or chemical capture. However, the coupled effects of surfactants and carbonation processes on cement paste remain unclear. This study investigated the effects of carbonation mixing, carbonation curing, and surfactant incorporation on the carbonation efficiency, microstructure, and mechanical properties of cement paste. A total of 192 specimens were prepared, with 12 specimens for each experimental condition. Tween 20 and TEPA were used as nonionic and amine-based surfactants, respectively. Carbonation mixing and carbonation curing were applied as the main carbonation variables. The experimental program included flow tests, isothermal calorimetry, FT-IR, compressive strength tests, thermogravimetric analysis, X-ray diffraction, mercury intrusion porosimetry, and FE-SEM/EDS. A baseline-corrected carbonation efficiency index was proposed for TGA-based carbonation assessment to reduce the effects of background mass loss and overlapping thermal decomposition. Tween 20 enhanced flowability, whereas TEPA reduced flowability, particularly under carbonation mixing. Carbonation mixing accelerated early hydration through the formation of fine CaCO3 particles, which served as nucleation sites and contributed to strength development. Con-CMNC exhibited the highest compressive strength, reaching 38.33 MPa at 7 days and 48.95 MPa at 28 days. In contrast, TEPA-containing specimens exhibited approximately 30–36% lower strength than the corresponding control specimens. Carbonation curing increased carbonation products but decreased compressive strength because of increased porosity, harmful pore development, and decalcification of hydration products. MIP results indicated that surfactant incorporation increased the porosity of cement paste. TP-NMNC had a porosity of 23.44%, approximately 36.1% higher than Con-NMNC. TP-NMCC had a porosity of 29.34%, approximately 20.7% higher than Con-NMCC. TGA, FT-IR, XRD, and FE-SEM/EDS confirmed that carbonation processes promoted CaCO3 formation and reduced the relative contribution of CH. The baseline-corrected TGA index increased from 1.158 for Con-NMNC to 2.461 for Con-CMNC and 3.742 for Con-CMCC, corresponding to increases of approximately 112.5% and 223.1%, respectively. TP-CMCC exhibited the highest index of 4.193, which was approximately 262.1% higher than Con-NMNC and 12.1% higher than Con-CMCC. This result suggests that TEPA enhanced CO2-related reactions through amine–CO2 interactions. However, the improved carbonation efficiency of TEPA-containing specimens was accompanied by reduced mechanical performance because of increased porosity and delayed hydration. Correlation and ANOVA results demonstrated that the carbonation process type had a stronger influence on pore structure and compressive strength than the surfactant type. TOPSIS-based evaluation identified TW-CMCC as the most balanced condition in terms of carbonation efficiency and compressive strength. Overall, surfactant effects were governed by the interaction between surfactant type and carbonation process. TEPA was more favorable for enhancing carbonation efficiency, whereas Tween 20 was more suitable for balancing carbonation performance and mechanical properties. Therefore, surfactant-assisted carbonation should be designed by jointly considering CO2 uptake, hydration behavior, pore-structure stability, and compressive strength. These results highlight the need to optimize surfactant-assisted carbonation by balancing chemical CO2 uptake with microstructural stability. The proposed assessment approach can support the selection of suitable surfactant– carbonation process combinations for low-carbon cement-based materials.

목차 (Table of Contents)

• 제 1 장 서 론 1
• 1.1 연구 배경 및 필요성 1
• 1.2 선행 연구 3
• 1.3 연구 목적 7
• 제 2 장 시멘트 페이스트의 탄산화 메커니즘 8
• 2.1 탄산화 배합 기술 9
• 2.2 탄산화 양생 기술 10
• 2.3 계면활성제 혼입 탄산화 기술 11
• 제 3 장 실험 방법 12
• 3.1 시험체 제작 12
• 3.1.1 실험 재료 준비 12
• 3.1.2 실험 매개변수 설정 14
• 3.1.3 실험 시험체 제작 16
• 3.2 시멘트 페이스트의 초기 수화 특성 18
• 3.2.1 흐름 시험(Flow test) 18
• 3.2.2 수화열(Hydration heat) 18
• 3.2.3 푸리에 변환 분광법(FT-IR) 18
• 3.3 시멘트 페이스트의 압축강도 19
• 3.4 내부구조 분석 20
• 3.4.1 열 중량 분석(TGA) 21
• 3.4.2 X선 회절 분석(XRD) 21
• 3.4.3 수은 압입 기공 분석(MIP) 21
• 3.4.4 전계방출형 주사전자현미경 분석(FE-SEM and EDS) 21
• 제 4 장 실험 결과 22
• 4.1 시멘트 페이스트의 초기 수화 특성 실험 결과 22
• 4.1.1 계면활성제 및 탄산화 배합에 따른 유동성 변화 22
• 4.1.2 계면활성제 및 탄산화 배합에 따른 초기 수화열 측정 24
• 4.1.3 초기 수화·탄산화 생성물의 FT-IR 분석 결과 27
• 4.2 탄산화 공정 및 계면활성제 혼입에 따른 압축강도 변화 29
• 4.3 내부구조 분석 결과 31
• 4.3.1 TGA 기반 탄산화 거동 및 탄산화 효율 정량적 분석 31
• 4.3.2 XRD 기반 시멘트 페이스트의 결정상 변화 42
• 4.3.3 MIP 기반 시멘트 페이스트의 공극 구조 분석 45
• 4.3.4 FE-SEM/EDS 기반 미세구조 및 원소 분포 특성 48
• 4.4 실험 결과 상관관계 분석 및 일원 분산분석 59
• 4.4.1 피어슨 및 스피어먼 상관관계 분석 59
• 4.4.2 일원 분산분석(One-way ANOVA) 62
• 4.5 탄산화 효율–압축강도 균형 성능 평가 65
• 제 5 장 결 론 68
• 참 고 문 헌 70