Pub Date : 2024-11-21DOI: 10.1016/j.cemconres.2024.107733
Daniel Lahmann, Sylvia Keßler
Autogenous self-healing can close cracks in water-retaining concrete structures. However, its inconsistent efficiency in building practice indicates that the underlying processes are not fully understood. Therefore, this study characterizes reactive transport through cracked concrete and models it using PHREEQC to develop a comprehensive understanding of chemical processes promoting autogenous self-healing. Driven by the dissolution of portlandite, the main cause of healing is the precipitation of CaCO3, which contributes to a crack closure of up to 113 μm. This process is supported by the formation of M-S-H and C-S-H. As self-healing progresses, the rates of dissolution and precipitation processes that promote healing decrease exponentially. At initial flow rates >2 L h−1, CaCO3 precipitation is favored towards the crack outlet. At lower initial flow rates, the formation of CaCO3 shifts towards the crack inlet. These findings underscore the need to reconsider the reliance on effective healing in practical applications.
{"title":"Reactive transport modelling of autogenous self-healing in cracked concrete","authors":"Daniel Lahmann, Sylvia Keßler","doi":"10.1016/j.cemconres.2024.107733","DOIUrl":"https://doi.org/10.1016/j.cemconres.2024.107733","url":null,"abstract":"Autogenous self-healing can close cracks in water-retaining concrete structures. However, its inconsistent efficiency in building practice indicates that the underlying processes are not fully understood. Therefore, this study characterizes reactive transport through cracked concrete and models it using PHREEQC to develop a comprehensive understanding of chemical processes promoting autogenous self-healing. Driven by the dissolution of portlandite, the main cause of healing is the precipitation of CaCO<ce:inf loc=\"post\">3</ce:inf>, which contributes to a crack closure of up to 113 μm. This process is supported by the formation of M-S-H and C-S-H. As self-healing progresses, the rates of dissolution and precipitation processes that promote healing decrease exponentially. At initial flow rates >2 L h<ce:sup loc=\"post\">−1</ce:sup>, CaCO<ce:inf loc=\"post\">3</ce:inf> precipitation is favored towards the crack outlet. At lower initial flow rates, the formation of CaCO<ce:inf loc=\"post\">3</ce:inf> shifts towards the crack inlet. These findings underscore the need to reconsider the reliance on effective healing in practical applications.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"14 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2024-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-20DOI: 10.1016/j.cemconres.2024.107710
Yanliang Ji, Ursula Pott, Alexander Mezhov, Christiane Rößler, Dietmar Stephan
Static yield stress is crucial for concrete, especially for 3D printed concrete, as it determines whether the bottom layer can support the load of the subsequent layers or withstand any potential impulses. A better understanding of the evolution of the static yield stress and its changing mechanism is therefore needed. Under the assumption that hydrate formation follows fractal patterns, this work proposes a model for simulating static yield stress that links the hydration process and bridging possibility. To validate the model, parameters were first obtained from the BNG (Boundary Nucleation Growth) equation fitted with calorimetry data, and the relation of associated hydration rates to sound speed variation rate was analyzed. Results showed that the proposed model predicts well the static yield stress obtained with a penetration test, under varying water-cement ratios and accelerator conditions. The fitted parameter β was found to correlate with size and morphology of the hydration products, suggesting that the model can not only simulate the static yield stress, but also capture the structural build-up information. Furthermore, the decrease in fractal-related β implies that more compact hydrates are formed during hydration.
静态屈服应力对混凝土，尤其是 3D 打印混凝土至关重要，因为它决定了底层能否支撑后续层的负荷或承受任何潜在的冲击。因此，需要更好地了解静屈服应力的演变及其变化机制。根据水合物形成遵循分形模式的假设，本研究提出了一个模拟静屈服应力的模型，该模型将水化过程和架桥可能性联系在一起。为验证该模型，首先根据量热数据拟合 BNG（边界成核增长）方程获得参数，并分析相关水化率与声速变化率的关系。结果表明，在不同的水灰比和促进剂条件下，所提出的模型能很好地预测通过渗透试验获得的静屈服应力。拟合参数 β 与水化产物的尺寸和形态相关，表明该模型不仅能模拟静屈服应力，还能捕捉到结构堆积信息。此外，与分形相关的 β 的减小意味着在水化过程中形成了更紧密的水合物。
{"title":"Modelling and experimental study on static yield stress evolution and structural build-up of cement paste in early stage of cement hydration","authors":"Yanliang Ji, Ursula Pott, Alexander Mezhov, Christiane Rößler, Dietmar Stephan","doi":"10.1016/j.cemconres.2024.107710","DOIUrl":"https://doi.org/10.1016/j.cemconres.2024.107710","url":null,"abstract":"Static yield stress is crucial for concrete, especially for 3D printed concrete, as it determines whether the bottom layer can support the load of the subsequent layers or withstand any potential impulses. A better understanding of the evolution of the static yield stress and its changing mechanism is therefore needed. Under the assumption that hydrate formation follows fractal patterns, this work proposes a model for simulating static yield stress that links the hydration process and bridging possibility. To validate the model, parameters were first obtained from the BNG (Boundary Nucleation Growth) equation fitted with calorimetry data, and the relation of associated hydration rates to sound speed variation rate was analyzed. Results showed that the proposed model predicts well the static yield stress obtained with a penetration test, under varying water-cement ratios and accelerator conditions. The fitted parameter β was found to correlate with size and morphology of the hydration products, suggesting that the model can not only simulate the static yield stress, but also capture the structural build-up information. Furthermore, the decrease in fractal-related β implies that more compact hydrates are formed during hydration.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"18 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-20DOI: 10.1016/j.cemconres.2024.107675
Xuan Gao, Qing-feng Liu, Yuxin Cai, Liang-yu Tong, Zesen Peng, Qing Xiang Xiong, Geert De Schutter
The interfacial transition zone (ITZ), located between aggregate and cement paste, has the features of high porosity, low unhydrated cement content, and enrichment of calcium hydroxide crystals (CH) and is often regarded as the weak link in cement-based materials. The present study is devoted to investigating the influence of multiple mechanisms or factors on ITZ formation, including the wall effect, ion transport, and aggregate features. A new modelling system is proposed to assess the interactions between these mechanisms or factors. The time-spatial distribution of hydration products and pores is studied by considering the reaction-diffusion-crystallization process of a non-uniformly distributed cement. Based on the developed model, the effects of individual mechanisms and their interactions on ITZ formation were clarified. The results indicated that the wall effect would determine the spatial distribution of cement and most hydration products due to the repulsion of aggregates on cement particles. The ion transport would influence the time evolution and redistribution of hydration products, which couples with the role of the wall effect. It was also found that aggregate features, including spacing and surface roughness, can affect the distribution of cement and the heterogeneity of cement-based materials, which works synergistically with the wall effect.
{"title":"A new model for investigating the formation of interfacial transition zone in cement-based materials","authors":"Xuan Gao, Qing-feng Liu, Yuxin Cai, Liang-yu Tong, Zesen Peng, Qing Xiang Xiong, Geert De Schutter","doi":"10.1016/j.cemconres.2024.107675","DOIUrl":"https://doi.org/10.1016/j.cemconres.2024.107675","url":null,"abstract":"The interfacial transition zone (ITZ), located between aggregate and cement paste, has the features of high porosity, low unhydrated cement content, and enrichment of calcium hydroxide crystals (CH) and is often regarded as the weak link in cement-based materials. The present study is devoted to investigating the influence of multiple mechanisms or factors on ITZ formation, including the wall effect, ion transport, and aggregate features. A new modelling system is proposed to assess the interactions between these mechanisms or factors. The time-spatial distribution of hydration products and pores is studied by considering the reaction-diffusion-crystallization process of a non-uniformly distributed cement. Based on the developed model, the effects of individual mechanisms and their interactions on ITZ formation were clarified. The results indicated that the wall effect would determine the spatial distribution of cement and most hydration products due to the repulsion of aggregates on cement particles. The ion transport would influence the time evolution and redistribution of hydration products, which couples with the role of the wall effect. It was also found that aggregate features, including spacing and surface roughness, can affect the distribution of cement and the heterogeneity of cement-based materials, which works synergistically with the wall effect.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"62 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142678321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-20DOI: 10.1016/j.cemconres.2024.107729
Binmeng Chen, Xu Fang, Yuyang Zhao, Zongjin Li
In recycling and reusing construction waste, carbonation of recycled concrete fine (RCF) has been successfully applied to produce value-added products, such as silica nanoparticles, via the breaking of calcium silicate hydrate (C-S-H) structure and condensation of silicate chains. However, the intricacies of carbonation of RCF with varying calcium to silicon (C/S) ratios and their implications on the size of generated silica nanoparticles remain unknown. In this work, we developed an optimized carbonation method at high water to solid ratio to fabricate silica nanoparticles from C-S-H with different C/S ratios. The particle size of silica nanoparticles was found to gradually decrease with the increased C/S ratio of C-S-H. Since as C/S ratio increased, silicate in Q3 state shifted to Q1 state and the silicate chain became shorter, shifting from long-range, disordered to short-range, ordered. As the disordered self-seeding growth of long silicate chains derived from C-S-H continued, the Si-O-Si network of silica nanoparticles became chaotic, leaving more unreacted Si-OH on its surface. On the contrary, the short silicate chains displayed higher possibility of condensation, making nanoparticles with a smaller diameter.
{"title":"Ca/Si-dependent size of silica nanoparticles derived from C-S-H at high water to solid ratio","authors":"Binmeng Chen, Xu Fang, Yuyang Zhao, Zongjin Li","doi":"10.1016/j.cemconres.2024.107729","DOIUrl":"https://doi.org/10.1016/j.cemconres.2024.107729","url":null,"abstract":"In recycling and reusing construction waste, carbonation of recycled concrete fine (RCF) has been successfully applied to produce value-added products, such as silica nanoparticles, via the breaking of calcium silicate hydrate (C-S-H) structure and condensation of silicate chains. However, the intricacies of carbonation of RCF with varying calcium to silicon (C/S) ratios and their implications on the size of generated silica nanoparticles remain unknown. In this work, we developed an optimized carbonation method at high water to solid ratio to fabricate silica nanoparticles from C-S-H with different C/S ratios. The particle size of silica nanoparticles was found to gradually decrease with the increased C/S ratio of C-S-H. Since as C/S ratio increased, silicate in Q<ce:sup loc=\"post\">3</ce:sup> state shifted to Q<ce:sup loc=\"post\">1</ce:sup> state and the silicate chain became shorter, shifting from long-range, disordered to short-range, ordered. As the disordered self-seeding growth of long silicate chains derived from C-S-H continued, the Si-O-Si network of silica nanoparticles became chaotic, leaving more unreacted Si-OH on its surface. On the contrary, the short silicate chains displayed higher possibility of condensation, making nanoparticles with a smaller diameter.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"16 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142679139","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-18DOI: 10.1016/j.cemconres.2024.107727
Lifu Yang, Zhenguo Shi, Kai Li, Xiang Hu, Caijun Shi
This study presents a homogenization approach to understand and simulate the heterogeneous expansion of irregularly shaped aggregate induced by alkali-silica reaction (ASR). The analysis employs a cubic representative volume element (RVE) containing a single reactive aggregate with an arbitrary shape embedded in a mortar matrix. At the aggregate level, ASR expansion is characterized by applying a homogeneous volumetric strain inside the internal structure of the reactive aggregate based on a first-order reaction kinetics. On the RVE scale, ASR expansion is formulated as a series of diffusion processes involving the formation of ASR products and their resulting expansion. By discretizing the RVE, a homogenization approach was proposed to link the homogeneous expansion rate at the aggregate level with the heterogeneous expansion strain at the RVE level. The model captures the heterogeneity of ASR expansion produced by reactive aggregate with arbitrary geometries by assigning anisotropic expansion capacity in different directions as a function of aggregate volume and size. The model was calibrated and validated using experimental data from literature. Results demonstrate that ASR expansion increases with aggregate size in the expansion direction for a given aggregate volume, and also with overall aggregate volume for a constant aggregate size in expansion direction. In addition, the simulations show that ASR-induced cracks in the mortar matrix initially form around the surface of reactive aggregate, particularly along the major axis (the direction of the maximum aggregate length) and around sharp corners of the irregularly shaped aggregate.
本研究提出了一种均质化方法，用于理解和模拟碱硅反应（ASR）诱发的不规则形状骨料的异质膨胀。分析采用了一个立方代表体积元素（RVE），其中包含一个嵌入砂浆基质中的任意形状的单个反应骨料。在骨料层面，根据一阶反应动力学，通过在反应骨料内部结构中施加均匀体积应变来描述 ASR 膨胀。在 RVE 尺度上，ASR 膨胀被表述为一系列涉及 ASR 产物形成及其膨胀的扩散过程。通过对 RVE 进行离散化，提出了一种均质化方法，将集料层面的均质膨胀率与 RVE 层面的异质膨胀应变联系起来。该模型通过将不同方向的各向异性膨胀能力作为骨料体积和尺寸的函数，捕捉了任意几何形状的反应骨料产生的 ASR 膨胀的异质性。利用文献中的实验数据对该模型进行了校准和验证。结果表明，在给定骨料体积的情况下，ASR 的膨胀率随骨料体积在膨胀方向上的增大而增大；在骨料体积不变的情况下，ASR 的膨胀率也随骨料体积在膨胀方向上的增大而增大。此外，模拟结果表明，砂浆基体中由 ASR 引起的裂缝最初形成于活性骨料表面周围，特别是沿主轴（最大骨料长度方向）和不规则形状骨料的尖角周围。
{"title":"Expansion of irregularly shaped aggregate induced by alkali-silica reaction: Insights from numerical modeling","authors":"Lifu Yang, Zhenguo Shi, Kai Li, Xiang Hu, Caijun Shi","doi":"10.1016/j.cemconres.2024.107727","DOIUrl":"https://doi.org/10.1016/j.cemconres.2024.107727","url":null,"abstract":"This study presents a homogenization approach to understand and simulate the heterogeneous expansion of irregularly shaped aggregate induced by alkali-silica reaction (ASR). The analysis employs a cubic representative volume element (RVE) containing a single reactive aggregate with an arbitrary shape embedded in a mortar matrix. At the aggregate level, ASR expansion is characterized by applying a homogeneous volumetric strain inside the internal structure of the reactive aggregate based on a first-order reaction kinetics. On the RVE scale, ASR expansion is formulated as a series of diffusion processes involving the formation of ASR products and their resulting expansion. By discretizing the RVE, a homogenization approach was proposed to link the homogeneous expansion rate at the aggregate level with the heterogeneous expansion strain at the RVE level. The model captures the heterogeneity of ASR expansion produced by reactive aggregate with arbitrary geometries by assigning anisotropic expansion capacity in different directions as a function of aggregate volume and size. The model was calibrated and validated using experimental data from literature. Results demonstrate that ASR expansion increases with aggregate size in the expansion direction for a given aggregate volume, and also with overall aggregate volume for a constant aggregate size in expansion direction. In addition, the simulations show that ASR-induced cracks in the mortar matrix initially form around the surface of reactive aggregate, particularly along the major axis (the direction of the maximum aggregate length) and around sharp corners of the irregularly shaped aggregate.","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"10 1","pages":""},"PeriodicalIF":11.4,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142670832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-16DOI: 10.1016/j.cemconres.2024.107726
Xin Zhao , Lin Wang , Qinfei Li , Heng Chen , Shuangrong Liu , Pengkun Hou , Jiayuan Ye , Yan Pei , Xu Wu , Jianfeng Yuan , Haozhong Gao , Bo Yang
Establishing a realistic three-dimensional (3D) microstructure is a crucial step for studying microstructure development of hardened cement pastes. However, acquiring 3D microstructural images for cement often involves high costs and quality compromises. This paper proposes a generative adversarial networks-based method for generating 3D microstructures from a single two-dimensional (2D) image, capable of producing high-quality and realistic 3D images at low cost. In the method, a framework (CEM3DMG) is designed to synthesize 3D images by learning microstructural information from a 2D cross-sectional image. Experimental results show that CEM3DMG can generate realistic 3D images of large size. Visual observation confirms that the generated 3D images exhibit similar microstructural features to the 2D images, including similar pore distribution and particle morphology. Furthermore, quantitative analysis reveals that reconstructed 3D microstructures closely match the real 2D microstructure in terms of gray level histogram, phase proportions, and pore size distribution.
{"title":"3D microstructural generation from 2D images of cement paste using generative adversarial networks","authors":"Xin Zhao , Lin Wang , Qinfei Li , Heng Chen , Shuangrong Liu , Pengkun Hou , Jiayuan Ye , Yan Pei , Xu Wu , Jianfeng Yuan , Haozhong Gao , Bo Yang","doi":"10.1016/j.cemconres.2024.107726","DOIUrl":"10.1016/j.cemconres.2024.107726","url":null,"abstract":"<div><div>Establishing a realistic three-dimensional (3D) microstructure is a crucial step for studying microstructure development of hardened cement pastes. However, acquiring 3D microstructural images for cement often involves high costs and quality compromises. This paper proposes a generative adversarial networks-based method for generating 3D microstructures from a single two-dimensional (2D) image, capable of producing high-quality and realistic 3D images at low cost. In the method, a framework (CEM3DMG) is designed to synthesize 3D images by learning microstructural information from a 2D cross-sectional image. Experimental results show that CEM3DMG can generate realistic 3D images of large size. Visual observation confirms that the generated 3D images exhibit similar microstructural features to the 2D images, including similar pore distribution and particle morphology. Furthermore, quantitative analysis reveals that reconstructed 3D microstructures closely match the real 2D microstructure in terms of gray level histogram, phase proportions, and pore size distribution.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107726"},"PeriodicalIF":10.9,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142642665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study assessed 40 industrial clinkers from 16 cement plants, determining their physical, chemical, and mineralogical properties and the corresponding cements' strength development and hydration kinetics. Pearson's statistical analysis identified key factors influencing clinker and cement properties. Clinker composition ranged within 56.5–73.9% C₃S, 4.1–24.5% C₂S, 0.8–8.4% C₃A, and 7.4–13.9% C₄AF. The sulfate-alkali ratio significantly impacted C₃A content and polymorphism. Alite crystal size was directly influenced by the CaO content and the sulfate-alkali ratio and inversely by the MgO, K₂O, and F− contents. Clinker grindability was directly affected by the C₃S crystal size and the sulfate-alkali ratio while inversely impacted by the MgO and K₂O contents. Key parameters for early cement hydration included fineness and K₂O content (positive) and C₃S crystal size (negative); larger C3S crystal size negatively affected cement early strength, while MnO2 and K2O presence improved 1-day strength. For 28-day strength, increasing cement fineness and K2O content were detrimental.
{"title":"Unveiling the key factors for clinker reactivity and cement performance: A physic-chemical and performance investigation of 40 industrial clinkers","authors":"J.S. Andrade Neto , I.C. Carvalho , P.J.M. Monteiro , P.R. de Matos , A.P. Kirchheim","doi":"10.1016/j.cemconres.2024.107717","DOIUrl":"10.1016/j.cemconres.2024.107717","url":null,"abstract":"<div><div>This study assessed 40 industrial clinkers from 16 cement plants, determining their physical, chemical, and mineralogical properties and the corresponding cements' strength development and hydration kinetics. Pearson's statistical analysis identified key factors influencing clinker and cement properties. Clinker composition ranged within 56.5–73.9% C₃S, 4.1–24.5% C₂S, 0.8–8.4% C₃A, and 7.4–13.9% C₄AF. The sulfate-alkali ratio significantly impacted C₃A content and polymorphism. Alite crystal size was directly influenced by the CaO content and the sulfate-alkali ratio and inversely by the MgO, K₂O, and F<sup>−</sup> contents. Clinker grindability was directly affected by the C₃S crystal size and the sulfate-alkali ratio while inversely impacted by the MgO and K₂O contents. Key parameters for early cement hydration included fineness and K₂O content (positive) and C₃S crystal size (negative); larger C<sub>3</sub>S crystal size negatively affected cement early strength, while MnO<sub>2</sub> and K<sub>2</sub>O presence improved 1-day strength. For 28-day strength, increasing cement fineness and K<sub>2</sub>O content were detrimental.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107717"},"PeriodicalIF":10.9,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142637244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-11DOI: 10.1016/j.cemconres.2024.107716
Zengliang Yue , Zixian Su , Partha P. Paul , Alastair T.M. Marsh , Alice Macente , Marco Di Michiel , John L. Provis , Philip J. Withers , Susan A. Bernal
The effects of CO2 exposure on sodium sulfate-activated blast furnace slag cement paste have been characterised by X-ray (attenuation) computed tomography revealing changes in micron-scale pore structure, and X-ray diffraction computed tomography (XRD-CT) elucidating changes in the spatial distribution of crystalline and semi-crystalline phases. Accelerated carbonation reduced ettringite volumes and induced formation of hydrotalcite, demonstrating the critical role of Mg-Al-SO4-layered double hydroxide phases in the CO2 uptake of these cements. These changes yield a refinement of small pores and increase the overall porosity, reaching values comparable to those of blended Portland cements. Formation factor values were determined considering the pore solution electrical resistivity, calculated from thermodynamic modelling, and the porosity. A correlation between simulated tortuosity and porosity is proposed to estimate the diffusion tortuosity and formation factor of sodium sulfate-activated slag pastes. This approach represents a significant step forward for assessing carbonation resistance and CO2 uptake capacity of cementitious pastes.
通过 X 射线（衰减）计算机断层扫描（XRD-CT）和 X 射线衍射计算机断层扫描（XRD-CT）分析了二氧化碳暴露对硫酸钠活化高炉矿渣水泥浆的影响，前者揭示了微米级孔隙结构的变化，后者阐明了结晶和半结晶相空间分布的变化。加速碳化减少了埃特林岩的体积，并诱导形成了水滑石，证明了 Mg-Al-SO4 层状双氢氧化物相在这些水泥的二氧化碳吸收过程中起着关键作用。这些变化细化了小孔并增加了整体孔隙率，达到了与混合波特兰水泥相当的数值。根据热力学模型计算出的孔隙溶液电阻率和孔隙率确定了形成因子值。提出了模拟迂回度和孔隙率之间的相关性，以估算硫酸钠活化矿渣浆的扩散迂回度和形成系数。这种方法在评估水泥浆的碳化阻力和二氧化碳吸收能力方面迈出了重要一步。
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Pub Date : 2024-11-09DOI: 10.1016/j.cemconres.2024.107715
Nana Wen , Ziyou Yu , Vincent Hallet , Arne Peys , Dimitrios Sakellariou , Yiannis Pontikes
Alkali-activated Fe-rich non-ferrous metallurgical slags (AA-NFMS) emerge as a novel, sustainable cementitious binder, but durability performance is one of the crucial parameters to assess their success. This paper investigates the degradation mechanisms of AA-NFMS in 4 wt% acetic acid (AcH) solutions, commonly found in agricultural industries. The results indicated that upon AcH exposure, the amorphous structure of AA-NFMS is changed. This process is accompanied by the release of crucial elements, including Ca, Fe, and a smaller amount of Al and Si, resulting in the formation of a more polymerized network. Fe could precipitate near the formed cracks. EPMA and micro-CT revealed the important role of crack formation and the initial permeability of AA-NFMS on the degradation process. Additionally, strength change does not correlate with mass change but is closely related to the permeability. Notably, AA-NFMS with 10 wt% CaO demonstrates the highest strength after AcH exposure.
碱活化富铁有色冶金渣（AA-NFMS）是一种新型、可持续的水泥基粘结剂，但耐久性能是评估其成功与否的关键参数之一。本文研究了 AA-NFMS 在 4 wt% 的醋酸（AcH）溶液中的降解机制，醋酸常见于农业工业。结果表明，接触 AcH 后，AA-NFMS 的无定形结构发生了变化。这一过程伴随着关键元素的释放，包括钙、铁以及少量的铝和硅，从而形成了更加聚合的网络。铁可能会在形成的裂缝附近析出。EPMA 和显微 CT 显示了裂纹形成和 AA-NFMS 初始渗透性对降解过程的重要作用。此外，强度变化与质量变化无关，但与渗透性密切相关。值得注意的是，含有 10 wt% CaO 的 AA-NFMS 在暴露于 AcH 后强度最高。
{"title":"Degradation of alkali-activated Fe-rich slag in acetic acid","authors":"Nana Wen , Ziyou Yu , Vincent Hallet , Arne Peys , Dimitrios Sakellariou , Yiannis Pontikes","doi":"10.1016/j.cemconres.2024.107715","DOIUrl":"10.1016/j.cemconres.2024.107715","url":null,"abstract":"<div><div>Alkali-activated Fe-rich non-ferrous metallurgical slags (AA-NFMS) emerge as a novel, sustainable cementitious binder, but durability performance is one of the crucial parameters to assess their success. This paper investigates the degradation mechanisms of AA-NFMS in 4 wt% acetic acid (AcH) solutions, commonly found in agricultural industries. The results indicated that upon AcH exposure, the amorphous structure of AA-NFMS is changed. This process is accompanied by the release of crucial elements, including Ca, Fe, and a smaller amount of Al and Si, resulting in the formation of a more polymerized network. Fe could precipitate near the formed cracks. EPMA and micro-CT revealed the important role of crack formation and the initial permeability of AA-NFMS on the degradation process. Additionally, strength change does not correlate with mass change but is closely related to the permeability. Notably, AA-NFMS with 10 wt% CaO demonstrates the highest strength after AcH exposure.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107715"},"PeriodicalIF":10.9,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142596502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-08DOI: 10.1016/j.cemconres.2024.107704
Maximilian Löher , Neven Ukrainczyk , Andreas Bogner , Astrid Hirsch , Frank Dehn , Eduardus Koenders
A reactive transport model was employed to investigate the influence of multiple hydrate phases during acetic acid attack on Portland cement paste. The simulation accounted for the dissolution of primary cement hydrates like Ettringite, Portlandite and C-S-H, along with the formation of silica gel products impacting diffusivity. The simulations primarily utilized independent material parameters, though the effective specific surface area of C-S-H phases required adjustment, indicating that only a small fraction is active in bulk paste compared to experimental values obtained from powders. Experiments involved exposing hardened cement paste samples to acetic acid (pH = 3) for durations ranging from 35 to 84 days. The model predicted changes in mineral assemblages, porosity, and pore solution chemistry versus degradation depth and time. Comparison of calculated Ca and Si-contents with experimentally obtained values from XRF analysis demonstrated good agreement of within 6% error, highlighting the importance of considering multiple minerals.
{"title":"Reactive transport modeling of acetic acid-induced degradation in portland cement paste","authors":"Maximilian Löher , Neven Ukrainczyk , Andreas Bogner , Astrid Hirsch , Frank Dehn , Eduardus Koenders","doi":"10.1016/j.cemconres.2024.107704","DOIUrl":"10.1016/j.cemconres.2024.107704","url":null,"abstract":"<div><div>A reactive transport model was employed to investigate the influence of multiple hydrate phases during acetic acid attack on Portland cement paste. The simulation accounted for the dissolution of primary cement hydrates like Ettringite, Portlandite and C-S-H, along with the formation of silica gel products impacting diffusivity. The simulations primarily utilized independent material parameters, though the effective specific surface area of C-S-H phases required adjustment, indicating that only a small fraction is active in bulk paste compared to experimental values obtained from powders. Experiments involved exposing hardened cement paste samples to acetic acid (pH = 3) for durations ranging from 35 to 84 days. The model predicted changes in mineral assemblages, porosity, and pore solution chemistry versus degradation depth and time. Comparison of calculated Ca and Si-contents with experimentally obtained values from <span><math><mi>μ</mi></math></span>XRF analysis demonstrated good agreement of within 6% error, highlighting the importance of considering multiple minerals.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107704"},"PeriodicalIF":10.9,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142596504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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