Pub Date : 2025-02-11DOI: 10.1016/j.cemconres.2025.107823
Yuguang Mao , Zhenguo Shi , Xiang Hu , Amani Khaskhoussi , Caijun Shi
The overall effect of wet carbonation recycled concrete fines (RCF) on the chloride binding capacity of cement paste was quantitatively decoupled into the effect of paste pH reduction, and the contribution of each component (uncarbonated phase, CaCO3, silica gel) in the wet carbonated RCF. Results indicate that incorporating wet carbonated RCF decreases both the chemical and physical chloride binding capacity of the cement paste. The extent of the decrease in the former is significantly lower than that of the latter. The main factors determining the extent of the decrease in chloride binding capacity are the reduction of paste pH and the effect of silica gel. These two effects become significant with increasing carbonation degree of RCF, mainly with increasing carbonation time. Increasing the CO₂ flow rate during RCF wet carbonation effectively mitigates the negative impact on chloride binding capacity due to the increased aluminum content in the produced silica gel.
{"title":"Chloride binding of cement paste containing wet carbonated recycled concrete fines","authors":"Yuguang Mao , Zhenguo Shi , Xiang Hu , Amani Khaskhoussi , Caijun Shi","doi":"10.1016/j.cemconres.2025.107823","DOIUrl":"10.1016/j.cemconres.2025.107823","url":null,"abstract":"<div><div>The overall effect of wet carbonation recycled concrete fines (RCF) on the chloride binding capacity of cement paste was quantitatively decoupled into the effect of paste pH reduction, and the contribution of each component (uncarbonated phase, CaCO<sub>3</sub>, silica gel) in the wet carbonated RCF. Results indicate that incorporating wet carbonated RCF decreases both the chemical and physical chloride binding capacity of the cement paste. The extent of the decrease in the former is significantly lower than that of the latter. The main factors determining the extent of the decrease in chloride binding capacity are the reduction of paste pH and the effect of silica gel. These two effects become significant with increasing carbonation degree of RCF, mainly with increasing carbonation time. Increasing the CO₂ flow rate during RCF wet carbonation effectively mitigates the negative impact on chloride binding capacity due to the increased aluminum content in the produced silica gel.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107823"},"PeriodicalIF":10.9,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378352","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 : 2025-02-11DOI: 10.1016/j.cemconres.2025.107825
Xudong Zhao , Jian-Xin Lu , Weichen Tian , Martin Cyr , Arezki Tagnit-Hamou , Chi Sun Poon
Concrete suffers significant performance degradation when exposed to high temperatures. This study explored the beneficial role of waste glass powder (WGP) in mitigating thermal damage and ultra-high performance concrete (UHPC) after elevated temperature exposure. The mechanism was elucidated through the chemical and microstructure changes, the composition of hydrates after exposure to elevated temperatures, and the subsequent re-curing. The presence of WGP significantly enhanced the residual mechanical properties of UHPC due to more wollastonite generation. The WGP also facilitated the recovery of mechanical properties and surface morphology during the post-fire self-healing process. The microstructural results confirmed that the WGP promoted the formation of the wollastonite phase in the thermal-damaged UHPC by reacting with the dehydrated products. Thermodynamic simulations indicated that the incorporation of WGP in UHPC resulted in an increase of liquid phase and its early appearance at high temperatures led to the transformation of γ-C2S into more stable wollastonite phases. Meanwhile, the activation of unreacted WGP by limewater further generated secondary hydration products to reduce matrix porosity. These hydrates mainly consisted of C-(N)-S-H gels with a low calcium-to-silicon ratio (Ca/Si) and high sodium-to-silicon ratio (Na/Si) ratio, which could effectively fill the micropores and microcracks in UHPC. As a result, the densified microstructure induced by these regenerated C-(N)-S-H gels largely contributed to the recovery of the thermally damaged UHPC. The outcome of this study provides a decarbonization solution to address damages of UHPC exposed to fire conditions.
{"title":"Self-healing performance of thermally damaged ultra-high performance concrete: Rehydration and recovery mechanism","authors":"Xudong Zhao , Jian-Xin Lu , Weichen Tian , Martin Cyr , Arezki Tagnit-Hamou , Chi Sun Poon","doi":"10.1016/j.cemconres.2025.107825","DOIUrl":"10.1016/j.cemconres.2025.107825","url":null,"abstract":"<div><div>Concrete suffers significant performance degradation when exposed to high temperatures. This study explored the beneficial role of waste glass powder (WGP) in mitigating thermal damage and ultra-high performance concrete (UHPC) after elevated temperature exposure. The mechanism was elucidated through the chemical and microstructure changes, the composition of hydrates after exposure to elevated temperatures, and the subsequent re-curing. The presence of WGP significantly enhanced the residual mechanical properties of UHPC due to more wollastonite generation. The WGP also facilitated the recovery of mechanical properties and surface morphology during the post-fire self-healing process. The microstructural results confirmed that the WGP promoted the formation of the wollastonite phase in the thermal-damaged UHPC by reacting with the dehydrated products. Thermodynamic simulations indicated that the incorporation of WGP in UHPC resulted in an increase of liquid phase and its early appearance at high temperatures led to the transformation of γ-C<sub>2</sub>S into more stable wollastonite phases. Meanwhile, the activation of unreacted WGP by limewater further generated secondary hydration products to reduce matrix porosity. These hydrates mainly consisted of C-(N)-S-H gels with a low calcium-to-silicon ratio (Ca/Si) and high sodium-to-silicon ratio (Na/Si) ratio, which could effectively fill the micropores and microcracks in UHPC. As a result, the densified microstructure induced by these regenerated C-(N)-S-H gels largely contributed to the recovery of the thermally damaged UHPC. The outcome of this study provides a decarbonization solution to address damages of UHPC exposed to fire conditions.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107825"},"PeriodicalIF":10.9,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378354","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 : 2025-02-11DOI: 10.1016/j.cemconres.2025.107824
Kazuma Fukui, Saya Kobayashi, Satoru Takada
Aerated concrete exhibits anomalous water transport, similar to mortar and concrete. Several factors, including water sensitivity, air entrapment, and gravity, are considered to be the causes; however, they are currently not quantitatively understood. This study aimed to clarify the mechanisms underlying the anomalous absorption of aerated concrete through liquid absorption experiments and numerical simulations of liquid and air transfer. The experiments showed that, unlike mortar and concrete, aerated concrete exhibited decreasing absorption rates during the initial stage of absorption, even when organic liquids were absorbed. A comparison between the calculations of simultaneous air and liquid transfers and those of single-phase water transfer in a material revealed that increases in water content in the high-water-content region were significantly reduced by air-pressure buildup. Therefore, the water absorption of aerated concrete, which is characterized by coarse aerated pores, is sensitive to air entrapment in addition to the water sensitivity of the cement component.
{"title":"Air entrapment and reaction with absorbed liquids on the absorption of aerated concrete","authors":"Kazuma Fukui, Saya Kobayashi, Satoru Takada","doi":"10.1016/j.cemconres.2025.107824","DOIUrl":"10.1016/j.cemconres.2025.107824","url":null,"abstract":"<div><div>Aerated concrete exhibits anomalous water transport, similar to mortar and concrete. Several factors, including water sensitivity, air entrapment, and gravity, are considered to be the causes; however, they are currently not quantitatively understood. This study aimed to clarify the mechanisms underlying the anomalous absorption of aerated concrete through liquid absorption experiments and numerical simulations of liquid and air transfer. The experiments showed that, unlike mortar and concrete, aerated concrete exhibited decreasing absorption rates during the initial stage of absorption, even when organic liquids were absorbed. A comparison between the calculations of simultaneous air and liquid transfers and those of single-phase water transfer in a material revealed that increases in water content in the high-water-content region were significantly reduced by air-pressure buildup. Therefore, the water absorption of aerated concrete, which is characterized by coarse aerated pores, is sensitive to air entrapment in addition to the water sensitivity of the cement component.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107824"},"PeriodicalIF":10.9,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143387800","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}
To reduce cement's carbon footprint, there is growing interest in commercial adoption of sustainable SCMs such as calcined clays. However, the existing ASTM standard (R3 test, C1897) to test the reactivity of such clays takes up to 7 days and cannot be used for real-time quality control in an industrial setting. We address this issue by introducing a 5-min Ultra-Rapid Reactivity (UR2) test. By dissolving 47 clay specimens in 4 M NaOH solutions at 90 °C, we report that a dissolution index of 1.54Al + Si correlates strongly to the 7-day R3 heat (R2 = 0.92, RMSE = 94.1 J/g). This dissolution index also correlates to the 28-day compressive strength for 14 clay mixtures (R2 = 0.94, RMSE = 1.7 MPa). This UR2 test relies on colorimetry and can be conducted via off-the-shelf, low-cost cameras. Overall, our new UR2 test opens a pathway for real-time, low-cost quality control of calcined clays.
{"title":"UR2: Ultra-rapid reactivity test for real-time, low-cost quality control of calcined clays","authors":"Yujia Min, Hossein Kabir, Chirayu Kothari, M. Farjad Iqbal, Nishant Garg","doi":"10.1016/j.cemconres.2025.107806","DOIUrl":"10.1016/j.cemconres.2025.107806","url":null,"abstract":"<div><div>To reduce cement's carbon footprint, there is growing interest in commercial adoption of sustainable SCMs such as calcined clays. However, the existing ASTM standard (R<sup>3</sup> test, C1897) to test the reactivity of such clays takes up to 7 days and cannot be used for real-time quality control in an industrial setting. We address this issue by introducing a 5-min Ultra-Rapid Reactivity (UR<sup>2</sup>) test. By dissolving 47 clay specimens in 4 M NaOH solutions at 90 °C, we report that a dissolution index of 1.54Al + Si correlates strongly to the 7-day R<sup>3</sup> heat (R<sup>2</sup> = 0.92, RMSE = 94.1 J/g). This dissolution index also correlates to the 28-day compressive strength for 14 clay mixtures (R<sup>2</sup> = 0.94, RMSE = 1.7 MPa). This UR<sup>2</sup> test relies on colorimetry and can be conducted via off-the-shelf, low-cost cameras. Overall, our new UR<sup>2</sup> test opens a pathway for real-time, low-cost quality control of calcined clays.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107806"},"PeriodicalIF":10.9,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378353","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}
Pub Date : 2025-02-10DOI: 10.1016/j.cemconres.2025.107811
Tianfeng Zhou , Haotian Duan , Beibei Li , Yuxia Pang , Hongming Lou , Dongjie Yang , Xueqing Qiu
The challenge of compatibility between polycarboxylate superplasticizer (PCE) and β-naphthalene sulfonate superplasticizer (BNS) remains an enduring puzzle, requiring a comprehensive understanding of their interaction mechanism. In our study, the macroscopic properties, microscopic interfacial adsorption, and intermolecular forces are investigated in detail to elucidate the interaction between PCE and BNS. The results show that the dispersing ability of PCE and BNS decreases under different blending sequences. The increased adsorption of the blended superplasticizers indicates that PCE and BNS undergo synergistic adsorption on the surface of cement particles rather than competitive adsorption. Atomic force microscopy reveals a shift in the intermolecular forces of the blended superplasticizers from repulsion to attraction, including CH-π interactions and hydrophobic interactions. BNS adsorption on the PCE side chain results in the bending and collapse of the latter, which prevents PCE from providing steric hindrance. Moreover, PCE side chains wrap around BNS molecules, reducing the absolute value of zeta potential of cement particles' surfaces. The study, conducted through both experimental and theoretical methods, provides evidence that attractive forces between PCE and BNS have a disruptive influence on the original molecular structure.
{"title":"The interaction mechanism of polycarboxylate and β-naphthalene sulfonate superplasticizers: Synergistic adsorption rather than competitive adsorption","authors":"Tianfeng Zhou , Haotian Duan , Beibei Li , Yuxia Pang , Hongming Lou , Dongjie Yang , Xueqing Qiu","doi":"10.1016/j.cemconres.2025.107811","DOIUrl":"10.1016/j.cemconres.2025.107811","url":null,"abstract":"<div><div>The challenge of compatibility between polycarboxylate superplasticizer (PCE) and β-naphthalene sulfonate superplasticizer (BNS) remains an enduring puzzle, requiring a comprehensive understanding of their interaction mechanism. In our study, the macroscopic properties, microscopic interfacial adsorption, and intermolecular forces are investigated in detail to elucidate the interaction between PCE and BNS. The results show that the dispersing ability of PCE and BNS decreases under different blending sequences. The increased adsorption of the blended superplasticizers indicates that PCE and BNS undergo synergistic adsorption on the surface of cement particles rather than competitive adsorption. Atomic force microscopy reveals a shift in the intermolecular forces of the blended superplasticizers from repulsion to attraction, including CH-π interactions and hydrophobic interactions. BNS adsorption on the PCE side chain results in the bending and collapse of the latter, which prevents PCE from providing steric hindrance. Moreover, PCE side chains wrap around BNS molecules, reducing the absolute value of zeta potential of cement particles' surfaces. The study, conducted through both experimental and theoretical methods, provides evidence that attractive forces between PCE and BNS have a disruptive influence on the original molecular structure.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107811"},"PeriodicalIF":10.9,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143375811","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 : 2025-02-10DOI: 10.1016/j.cemconres.2025.107827
Minjie Jia , Xiangyi Chen , Zhichao Xu , Juncheng Wen , Yingzi Yang , Kunyang Yu , Yushi Liu
Regulating the resistivity of ultra-high-performance concrete (UHPC) infrastructure is crucial for endowing UHPC with intelligence and multifunctionality. In this study, we proposed a new approach to enhance the electrical conductivity of UHPC via high-temperature electric induction. When the temperature of electric-cured UHPC was heated to 90–130 °C, the resistivity dropped sharply. After electric curing, the resistivity of UHPC was significantly reduced from 8.7 MΩ·cm to 537.18 Ω·cm compared to that of steam-cured UHPC. It was confirmed that the tunneling effect and dielectric breakdown were the main reasons for the sudden resistivity drop during electric curing. Moreover, electrochemical impedance spectroscopy (EIS) and model experiments revealed the oriented deposition of new conductive products within the UHPC matrix. This approach also strengthened UHPC in 3 h comparable to 3-day steam curing of 90 °C. This work opened up a novel path in constructing effective conductive networks of cement-based materials.
{"title":"A new approach for constructing UHPC conductive pathways: Oriented deposition of conductive hydration products","authors":"Minjie Jia , Xiangyi Chen , Zhichao Xu , Juncheng Wen , Yingzi Yang , Kunyang Yu , Yushi Liu","doi":"10.1016/j.cemconres.2025.107827","DOIUrl":"10.1016/j.cemconres.2025.107827","url":null,"abstract":"<div><div>Regulating the resistivity of ultra-high-performance concrete (UHPC) infrastructure is crucial for endowing UHPC with intelligence and multifunctionality. In this study, we proposed a new approach to enhance the electrical conductivity of UHPC via high-temperature electric induction. When the temperature of electric-cured UHPC was heated to 90–130 °C, the resistivity dropped sharply. After electric curing, the resistivity of UHPC was significantly reduced from 8.7 MΩ·cm to 537.18 Ω·cm compared to that of steam-cured UHPC. It was confirmed that the tunneling effect and dielectric breakdown were the main reasons for the sudden resistivity drop during electric curing. Moreover, electrochemical impedance spectroscopy (EIS) and model experiments revealed the oriented deposition of new conductive products within the UHPC matrix. This approach also strengthened UHPC in 3 h comparable to 3-day steam curing of 90 °C. This work opened up a novel path in constructing effective conductive networks of cement-based materials.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107827"},"PeriodicalIF":10.9,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143375812","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 : 2025-02-08DOI: 10.1016/j.cemconres.2025.107789
Mohmad M. Thakur , N. Axel Henningsson , Jonas Engqvist , Pierre-Olivier Autran , Jonathan P. Wright , Ryan C. Hurley
Concrete features significant microstructural heterogeneity which affects its mechanical behavior. Strain localization in the matrix phase of concrete has received significant attention due to its relation to microcracking and our ability to quantify it with X-ray computed tomography (XRCT). In contrast, stresses in sand and aggregates remain largely unmeasured but remain critical for micromechanics-based theories of failure. Here, we use a combination of in-situ XRCT, 3D X-ray diffraction (3DXRD), and scanning 3DXRD to directly measure strain and stress within sand grains in two samples of mortar containing different sand volume fractions. Our results reveal that, in contrast to inclusion theories from continuum micromechanics, aggregates feature a broad distribution of average stresses and significant gradients in their internal stress fields. Our work furnishes the first known dataset with these quantitative stress measurements and motivates improvements in micromechanics models for concrete which can capture stress heterogeneity.
{"title":"Grain-scale stress heterogeneity in concrete from in-situ X-ray measurements","authors":"Mohmad M. Thakur , N. Axel Henningsson , Jonas Engqvist , Pierre-Olivier Autran , Jonathan P. Wright , Ryan C. Hurley","doi":"10.1016/j.cemconres.2025.107789","DOIUrl":"10.1016/j.cemconres.2025.107789","url":null,"abstract":"<div><div>Concrete features significant microstructural heterogeneity which affects its mechanical behavior. Strain localization in the matrix phase of concrete has received significant attention due to its relation to microcracking and our ability to quantify it with X-ray computed tomography (XRCT). In contrast, stresses in sand and aggregates remain largely unmeasured but remain critical for micromechanics-based theories of failure. Here, we use a combination of <em>in-situ</em> XRCT, 3D X-ray diffraction (3DXRD), and scanning 3DXRD to directly measure strain and stress within sand grains in two samples of mortar containing different sand volume fractions. Our results reveal that, in contrast to inclusion theories from continuum micromechanics, aggregates feature a broad distribution of average stresses and significant gradients in their internal stress fields. Our work furnishes the first known dataset with these quantitative stress measurements and motivates improvements in micromechanics models for concrete which can capture stress heterogeneity.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107789"},"PeriodicalIF":10.9,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349455","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}
The combined effects of water pressure and water penetration on the mechanical behavior of concrete under hydraulic loading were investigated. When concrete is subjected to water pressure, a saturated zone forms near the surface and gradually progresses toward the interior over time, resulting in a non-homogeneous hybrid state with a saturated envelope and humid core (hybrid saturated state) during the initial stages of hydraulic loading. However, the mechanical behavior of concrete with a hybrid saturated state has hardly been investigated. This study performed the experiments on concretes with water pressures (~50 MPa). The results show that concrete with a hybrid saturated state exhibits higher peak mechanical stress than unconfined concrete. In contrast, the peak mechanical stress of fully saturated concrete remains comparable to that of unconfined concrete. This indicates that water penetration strongly influences the triaxial strength of concrete under water pressure, especially in the initial stages of hydraulic loading.
{"title":"Mechanical behavior of concrete under high water pressure: Water penetration as a critical factor for mechanical properties","authors":"Atichon Kunawisarut , Yuichiro Kawabata , Mitsuyasu Iwanami","doi":"10.1016/j.cemconres.2025.107820","DOIUrl":"10.1016/j.cemconres.2025.107820","url":null,"abstract":"<div><div>The combined effects of water pressure and water penetration on the mechanical behavior of concrete under hydraulic loading were investigated. When concrete is subjected to water pressure, a saturated zone forms near the surface and gradually progresses toward the interior over time, resulting in a non-homogeneous hybrid state with a saturated envelope and humid core (hybrid saturated state) during the initial stages of hydraulic loading. However, the mechanical behavior of concrete with a hybrid saturated state has hardly been investigated. This study performed the experiments on concretes with water pressures (~50 MPa). The results show that concrete with a hybrid saturated state exhibits higher peak mechanical stress than unconfined concrete. In contrast, the peak mechanical stress of fully saturated concrete remains comparable to that of unconfined concrete. This indicates that water penetration strongly influences the triaxial strength of concrete under water pressure, especially in the initial stages of hydraulic loading.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107820"},"PeriodicalIF":10.9,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350543","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 : 2025-02-06DOI: 10.1016/j.cemconres.2025.107818
Yanrong Zhang , Xuesong Zhang , Zichen Lu , Kai Wu , Xiaopei Cai
Hydrophobic-modified silica fume (HSF) with superior dispersion was synthesized by coating silane onto SF surface. Its influence on cement hydration, microstructure and properties of cement pastes was investigated. Results indicated that the silane on SF surface visibly depressed pozzolanic reaction at early ages. HSF retarded cement hydration by adsorbing on cement surface and more importantly, by interacting with Ca2+ in aqueous phase. For the first time, the accumulation of calcium around HSF was observed, leading to the growth of needle-like C–S–H perpendicular to HSF surface and eventually evolved into loose honeycomb-like gels. These loose gels promoted pozzolanic reaction and cement hydration at late ages. TEM and XRD results revealed that silane incorporated itself into C–S–H and altered structural order. Furthermore, adding HSF increased capillary pore size but refined the inter-hydrate pores at late ages. HSF visibly decreased the compressive strength compared with SF; however, the difference diminished at late ages.
{"title":"New insight into the effects of silane-modified silica fume on the performance of cement pastes","authors":"Yanrong Zhang , Xuesong Zhang , Zichen Lu , Kai Wu , Xiaopei Cai","doi":"10.1016/j.cemconres.2025.107818","DOIUrl":"10.1016/j.cemconres.2025.107818","url":null,"abstract":"<div><div>Hydrophobic-modified silica fume (HSF) with superior dispersion was synthesized by coating silane onto SF surface. Its influence on cement hydration, microstructure and properties of cement pastes was investigated. Results indicated that the silane on SF surface visibly depressed pozzolanic reaction at early ages. HSF retarded cement hydration by adsorbing on cement surface and more importantly, by interacting with Ca<sup>2+</sup> in aqueous phase. For the first time, the accumulation of calcium around HSF was observed, leading to the growth of needle-like C–S–H perpendicular to HSF surface and eventually evolved into loose honeycomb-like gels. These loose gels promoted pozzolanic reaction and cement hydration at late ages. TEM and XRD results revealed that silane incorporated itself into C–S–H and altered structural order. Furthermore, adding HSF increased capillary pore size but refined the inter-hydrate pores at late ages. HSF visibly decreased the compressive strength compared with SF; however, the difference diminished at late ages.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107818"},"PeriodicalIF":10.9,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143191860","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 : 2025-02-04DOI: 10.1016/j.cemconres.2025.107819
Yuefeng Ma , Ming Jin , Fei Wang , Diederik Jacques , Xuyan Shen , Jian Zhang , Chang Gao , Haoyu Zeng , Jingwen Liu , Jiaping Liu
Transformation of C-S-H is crucial in the deterioration of concrete at high temperatures. This study investigates the composition, structure, and morphology of C-S-H from 30 °C to 1000 °C using in-situ heating XRD, TGA/TG-IR, in-situ heating XPS, and in-situ heating TEM combined with image recognition. The results reveal that during heating, C-S-H undergoes weakly and strongly bound water loss, dehydroxylation, and transformation into CaSiO3. During heating, the Si-O-Si bonds within C-S-H silicate chains remain highly stable. The primary change observed is the conversion of Si-OH groups into Si-O-Ca/Na following dehydroxylation. TEM morphology exhibits shrinkage and densification similar to ceramic sintering, with the overall process divided into five stages. The first three stages are dominated by dehydration and dehydroxylation, while the final two stages are governed by phase changes and liquid-phase sintering. The dehydration of C-S-H in the first stage has the greatest impact on shrinkage, while the fourth stage transforms the C-S-H morphology from foil-like to drop-like, having the largest effect on densification. Although the Ca/Si ratio of C-S-H remains constant during the heating, the crystallinity decreases. This study offers new insights into the mechanisms driving the transformation of C-S-H under heating.
{"title":"Heating-induced transformations in calcium silicate hydrate (C-S-H): In-situ investigations of composition, structure, and morphology","authors":"Yuefeng Ma , Ming Jin , Fei Wang , Diederik Jacques , Xuyan Shen , Jian Zhang , Chang Gao , Haoyu Zeng , Jingwen Liu , Jiaping Liu","doi":"10.1016/j.cemconres.2025.107819","DOIUrl":"10.1016/j.cemconres.2025.107819","url":null,"abstract":"<div><div>Transformation of C-S-H is crucial in the deterioration of concrete at high temperatures. This study investigates the composition, structure, and morphology of C-S-H from 30 °C to 1000 °C using in-situ heating XRD, TGA/TG-IR, in-situ heating XPS, and in-situ heating TEM combined with image recognition. The results reveal that during heating, C-S-H undergoes weakly and strongly bound water loss, dehydroxylation, and transformation into CaSiO<sub>3</sub>. During heating, the Si-O-Si bonds within C-S-H silicate chains remain highly stable. The primary change observed is the conversion of Si-OH groups into Si-O-Ca/Na following dehydroxylation. TEM morphology exhibits shrinkage and densification similar to ceramic sintering, with the overall process divided into five stages. The first three stages are dominated by dehydration and dehydroxylation, while the final two stages are governed by phase changes and liquid-phase sintering. The dehydration of C-S-H in the first stage has the greatest impact on shrinkage, while the fourth stage transforms the C-S-H morphology from foil-like to drop-like, having the largest effect on densification. Although the Ca/Si ratio of C-S-H remains constant during the heating, the crystallinity decreases. This study offers new insights into the mechanisms driving the transformation of C-S-H under heating.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"190 ","pages":"Article 107819"},"PeriodicalIF":10.9,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143083781","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}
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