Pub Date : 2025-02-18DOI: 10.1016/j.cemconres.2025.107837
Xuerun Li , Karen L. Scrivener
X-ray powder diffraction (XRD) was used to characterize and quantify nano-crystalline C-S-H in hydrated tricalcium silicate (C3S), Portland cement, and siliceous fly ash blended cement using Rietveld analysis with partial or no known crystal structure (PONKCS) coupled with thermalgravimetric analysis (TGA). Calibration of the C-S-H profile was carried out by minimizing bound water content detected by TGA and XRD using least square minimization. Validation of the results was achieved by independent methods such as TGA and mass balance calculation. The PONKCS analysis provided acceptable accuracy of the C-S-H content. H2O content in C-S-H was derived based on the C-S-H content and bound water. Comparison of the extracted profile showed that the C-S-H crystallinity increased with an increase in Ca/Si atomic ratio. The full phase assemblage of the hydrated samples was obtained. Challenges in applying PONKCS method in C-S-H determination were discussed.
{"title":"Quantification of nano-crystalline C-S-H in hydrated tricalcium silicate, Portland cement and fly ash cement using PONKCS method","authors":"Xuerun Li , Karen L. Scrivener","doi":"10.1016/j.cemconres.2025.107837","DOIUrl":"10.1016/j.cemconres.2025.107837","url":null,"abstract":"<div><div>X-ray powder diffraction (XRD) was used to characterize and quantify nano-crystalline C-S-H in hydrated tricalcium silicate (C<sub>3</sub>S), Portland cement, and siliceous fly ash blended cement using Rietveld analysis with partial or no known crystal structure (PONKCS) coupled with thermalgravimetric analysis (TGA). Calibration of the C-S-H profile was carried out by minimizing bound water content detected by TGA and XRD using least square minimization. Validation of the results was achieved by independent methods such as TGA and mass balance calculation. The PONKCS analysis provided acceptable accuracy of the C-S-H content. H<sub>2</sub>O content in C-S-H was derived based on the C-S-H content and bound water. Comparison of the extracted profile showed that the C-S-H crystallinity increased with an increase in Ca/Si atomic ratio. The full phase assemblage of the hydrated samples was obtained. Challenges in applying PONKCS method in C-S-H determination were discussed.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107837"},"PeriodicalIF":10.9,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429385","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 : 2025-02-16DOI: 10.1016/j.cemconres.2025.107809
Rodrigo Díaz Flores, Christian Hellmich, Bernhard Pichler
With the aim to identify the mechanisms governing nonlinear basic creep of concrete under uniaxial compression, a micromechanics model is presented. Extending the affinity concept for nonlinear creep, it describes that every microcrack incrementally increases the damage of concrete, leading to a step-wise increase of its compliance. Experimental data are taken from the literature. Strain and acoustic emission measurements from a multi-stage creep test are used to develop the model. This includes identification of microcrack evolution laws for both short-term load application and sustained loading. Strain measurements from four single-stage creep tests are used for model validation. It is concluded that nonlinear creep of concrete is governed by two mechanisms: (i) stress-induced stick–slip transition of viscous interfaces at the nanostructure of cement paste, which is phenomenologically accounted for by the affinity concept, and (ii) microcracking-induced damage, which is of major importance once the stress exceeds some 70% of the strength.
{"title":"Nonlinear creep of concrete: Stress-activated stick–slip transition of viscous interfaces and microcracking-induced damage","authors":"Rodrigo Díaz Flores, Christian Hellmich, Bernhard Pichler","doi":"10.1016/j.cemconres.2025.107809","DOIUrl":"10.1016/j.cemconres.2025.107809","url":null,"abstract":"<div><div>With the aim to identify the mechanisms governing nonlinear basic creep of concrete under uniaxial compression, a micromechanics model is presented. Extending the affinity concept for nonlinear creep, it describes that every microcrack incrementally increases the damage of concrete, leading to a step-wise increase of its compliance. Experimental data are taken from the literature. Strain and acoustic emission measurements from a multi-stage creep test are used to develop the model. This includes identification of microcrack evolution laws for both short-term load application and sustained loading. Strain measurements from four single-stage creep tests are used for model validation. It is concluded that nonlinear creep of concrete is governed by two mechanisms: (i) stress-induced stick–slip transition of viscous interfaces at the nanostructure of cement paste, which is phenomenologically accounted for by the affinity concept, and (ii) microcracking-induced damage, which is of major importance once the stress exceeds some 70% of the strength.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107809"},"PeriodicalIF":10.9,"publicationDate":"2025-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417499","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 : 2025-02-14DOI: 10.1016/j.cemconres.2025.107821
Liming Huang , Erik Bialik , Arezou Babaahmadi
The diffusion of chloride critically affects the durability of reinforced concrete in exposure environments. Hydrocalumite-like (AFm) phases can bind chlorides to form Friedel's salts, retarding chloride ingress. However, the stability and structural parameters of Friedel's salts with mixed-anion interlayers are not fully understood. First principles computation was performed to provide the energy-minimum crystal structures for Friedel's salt and AFm phases with various substitutions and water contents. It shows that the mixing of Cl− and OH− significantly changes the lattice parameters. However, the mixing of 1/2CO32− and Cl− anion presents little effect on structural parameter. It is energetically favourable and hardly measurable by XRD but decreases chloride binding capacity. The interlayer hydroxide ions show considerable flexibility in terms of occupied sites, which may be a key factor for the stability of AFm phases. The modelling results align with the the structural changes of Friedel's salts reported in previous experiments.
{"title":"Atomistic modelling of crystal structures of Friedel's salts Ca2Al(OH)6(Cl,CO3,OH)·mH2O: Its relation to chloride binding","authors":"Liming Huang , Erik Bialik , Arezou Babaahmadi","doi":"10.1016/j.cemconres.2025.107821","DOIUrl":"10.1016/j.cemconres.2025.107821","url":null,"abstract":"<div><div>The diffusion of chloride critically affects the durability of reinforced concrete in exposure environments. Hydrocalumite-like (AFm) phases can bind chlorides to form Friedel's salts, retarding chloride ingress. However, the stability and structural parameters of Friedel's salts with mixed-anion interlayers are not fully understood. First principles computation was performed to provide the energy-minimum crystal structures for Friedel's salt and AFm phases with various substitutions and water contents. It shows that the mixing of Cl<sup>−</sup> and OH<sup>−</sup> significantly changes the lattice parameters. However, the mixing of 1/2CO<sub>3</sub><sup>2−</sup> and Cl<sup>−</sup> anion presents little effect on structural parameter. It is energetically favourable and hardly measurable by XRD but decreases chloride binding capacity. The interlayer hydroxide ions show considerable flexibility in terms of occupied sites, which may be a key factor for the stability of AFm phases. The modelling results align with the the structural changes of Friedel's salts reported in previous experiments.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107821"},"PeriodicalIF":10.9,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143417504","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 : 2025-02-13DOI: 10.1016/j.cemconres.2025.107828
Minghui Jiang , Xiao Liu , Shiyu Li , Yurui Xu , Simai Wang , Lei Lu , Xinxin Li , Xinru Sun , Chunlei Xia , Ziming Wang , Suping Cui
The internal water migration within calcium silicate hydrate (C-S-H) in dry environments is considered to be the primary factor affecting the volume stability of cementitious materials. In this research, the in-situ polymerization product of plant polyphenol tannic acid (TA) was applied to modify C-S-H based on an organic-inorganic composite modification method. The chemical structure, microstructure, composition, dimensional changes and water migration characteristics of modified C-S-H were analyzed. Experimental results showed that TA improved the polymerization degree of siloxane chains in the C-S-H nanostructure, with a maximum improvement of 80.70%, and increased the interlayer spacing in the C-S-H structure, confirming the modification of C-S-H at the nanoscale, exhibited by 29Si Nuclear Magnetic Resonance (NMR), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). This modification by TA optimized the C-S-H nanostructure and microscopic pores, and increased the interlayer and gel pore water content, especially gel pore water increased by 56.53% compared to that of the unmodified C-S-H, revealed by nitrogen adsorption and 1H LF-NMR. In the dry environment, the blocking and cladding effects of TA on C-S-H effectively inhibited the gel water loss and reduced the drying shrinkage, especially at low TA concentration. This research aims to improve the volume stability of C-S-H by in-situ polymerization product of plant polyphenol, which provides new insights into improving the volume stability of cementitious materials.
{"title":"New insights into the improvement of volume stability: Plant polyphenol modified calcium silicate hydrate (C-S-H)","authors":"Minghui Jiang , Xiao Liu , Shiyu Li , Yurui Xu , Simai Wang , Lei Lu , Xinxin Li , Xinru Sun , Chunlei Xia , Ziming Wang , Suping Cui","doi":"10.1016/j.cemconres.2025.107828","DOIUrl":"10.1016/j.cemconres.2025.107828","url":null,"abstract":"<div><div>The internal water migration within calcium silicate hydrate (C-S-H) in dry environments is considered to be the primary factor affecting the volume stability of cementitious materials. In this research, the in-situ polymerization product of plant polyphenol tannic acid (TA) was applied to modify C-S-H based on an organic-inorganic composite modification method. The chemical structure, microstructure, composition, dimensional changes and water migration characteristics of modified C-S-H were analyzed. Experimental results showed that TA improved the polymerization degree of siloxane chains in the C-S-H nanostructure, with a maximum improvement of 80.70%, and increased the interlayer spacing in the C-S-H structure, confirming the modification of C-S-H at the nanoscale, exhibited by <sup>29</sup>Si Nuclear Magnetic Resonance (NMR), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM). This modification by TA optimized the C-S-H nanostructure and microscopic pores, and increased the interlayer and gel pore water content, especially gel pore water increased by 56.53% compared to that of the unmodified C-S-H, revealed by nitrogen adsorption and <sup>1</sup>H LF-NMR. In the dry environment, the blocking and cladding effects of TA on C-S-H effectively inhibited the gel water loss and reduced the drying shrinkage, especially at low TA concentration. This research aims to improve the volume stability of C-S-H by in-situ polymerization product of plant polyphenol, which provides new insights into improving the volume stability of cementitious materials.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107828"},"PeriodicalIF":10.9,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395194","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}
Limestone powder (LS) with large particle sizes is widely used, but its effect on water migration behavior remains unclear. This study investigates the influence of LS and viscosity-enhancing admixtures (VEAs) on the water migration behavior and water distribution in fresh cement paste using 1H low-field nuclear magnetic resonance (LF-NMR). Results indicate that LS increases the size of water migration channels, accelerates the water migration rate, and raises the bleeding ratio, while VEAs substantially mitigate the effects of LS. Compared to polyacrylamide, cellulose ether significantly slows down the water migration rate before 40 min, thereby reducing the bleeding ratio. Additionally, relaxation times were found to decrease during bleeding and can reflect the sedimentation process. It is confirmed that the pore structure of fresh paste exhibits fractal characteristics, with the fractal dimension closely correlating with water migration rates. The underlying mechanisms and their implications on material behavior are thoroughly analyzed and discussed.
{"title":"1H LF-NMR study on water migration behavior of fresh cement paste with limestone powder","authors":"Jing Qiao , Chunsheng Zhou , Jingjing Feng , Miao Miao , Yanliang Ji , Linan Gu","doi":"10.1016/j.cemconres.2025.107802","DOIUrl":"10.1016/j.cemconres.2025.107802","url":null,"abstract":"<div><div>Limestone powder (LS) with large particle sizes is widely used, but its effect on water migration behavior remains unclear. This study investigates the influence of LS and viscosity-enhancing admixtures (VEAs) on the water migration behavior and water distribution in fresh cement paste using <sup>1</sup>H low-field nuclear magnetic resonance (LF-NMR). Results indicate that LS increases the size of water migration channels, accelerates the water migration rate, and raises the bleeding ratio, while VEAs substantially mitigate the effects of LS. Compared to polyacrylamide, cellulose ether significantly slows down the water migration rate before 40 min, thereby reducing the bleeding ratio. Additionally, relaxation times were found to decrease during bleeding and can reflect the sedimentation process. It is confirmed that the pore structure of fresh paste exhibits fractal characteristics, with the fractal dimension closely correlating with water migration rates. The underlying mechanisms and their implications on material behavior are thoroughly analyzed and discussed.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107802"},"PeriodicalIF":10.9,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395196","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 : 2025-02-13DOI: 10.1016/j.cemconres.2025.107829
Thien Q. Tran , Rachel Cook , Olajide Ipindola , Ebenezer O. Fanijo , Aron Newman , Paul E. Stutzman , Alexander S. Brand
As carbon dioxide (CO2) sequestration technology begins to emerge in the construction and building materials sectors, industry stakeholders require quantifiable assurance mineralized CO2 content of emerging carbonated products. This study adapts a Digestion-Titration Method (DTM) for the determination of mineralized CO2 content in cementitious materials based on tests that were originally developed in the early 1900s. The experimental conditions were optimized with a systematic design of experiments (DOE) approach. The method utilizes hydrochloric acid to digest carbonate minerals (i.e., CaCO3, MgCO3) under vacuum conditions. The liberated CO2 from acid digestion is captured by a barium hydroxide solution to precipitate barium carbonate. Titration is used to quantify the remaining barium hydroxide, yielding a back-estimation of the total CO2 content. Mixtures of fixed compositions, portland cement, and a carbonated cementitious commercial product were employed to validate the proposed DTM method. DTM results were compared to thermogravimetric analysis (TGA) of the same samples. The outcomes of this work demonstrate that DTM can provide results consistent with TGA for samples containing a singular carbonate phase and yield more consistent quantification of mineralized CO2 for samples containing multiple phases.
{"title":"Measuring mineralized carbon in carbonate minerals and cementitious materials by an acid digestion-titration method","authors":"Thien Q. Tran , Rachel Cook , Olajide Ipindola , Ebenezer O. Fanijo , Aron Newman , Paul E. Stutzman , Alexander S. Brand","doi":"10.1016/j.cemconres.2025.107829","DOIUrl":"10.1016/j.cemconres.2025.107829","url":null,"abstract":"<div><div>As carbon dioxide (CO<sub>2</sub>) sequestration technology begins to emerge in the construction and building materials sectors, industry stakeholders require quantifiable assurance mineralized CO<sub>2</sub> content of emerging carbonated products. This study adapts a Digestion-Titration Method (DTM) for the determination of mineralized CO<sub>2</sub> content in cementitious materials based on tests that were originally developed in the early 1900s. The experimental conditions were optimized with a systematic design of experiments (DOE) approach. The method utilizes hydrochloric acid to digest carbonate minerals (<em>i.e.</em>, CaCO<sub>3</sub>, MgCO<sub>3</sub>) under vacuum conditions. The liberated CO<sub>2</sub> from acid digestion is captured by a barium hydroxide solution to precipitate barium carbonate. Titration is used to quantify the remaining barium hydroxide, yielding a back-estimation of the total CO<sub>2</sub> content. Mixtures of fixed compositions, portland cement, and a carbonated cementitious commercial product were employed to validate the proposed DTM method. DTM results were compared to thermogravimetric analysis (TGA) of the same samples. The outcomes of this work demonstrate that DTM can provide results consistent with TGA for samples containing a singular carbonate phase and yield more consistent quantification of mineralized CO<sub>2</sub> for samples containing multiple phases.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107829"},"PeriodicalIF":10.9,"publicationDate":"2025-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143395195","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.2025.107826
Jiawei Wang , Xiaohong Zhu , Jun Wang , Yang Chen , Yuanpeng Liu , Zhangli Hu , Jiaping Liu , Roya Maboudian , Paulo J.M. Monteiro
In cementitious materials, continuous hydration of mineral phases and creep always coexist, making it difficult to decouple the effect of hydration on creep measurements, which are invariably time-dependent. This study compares a real hydration (aging) system with an equivalent hydration (non-aging) system. In the non-aging system, the unhydrated phase was replaced with inert quartz at specific ages (1, 7, 28, and 91 days) to uncover the mechanism of clinker and supplementary cementitious materials (SCMs) hydration on creep. The results show that the hydration process of SCMs and morphology of calcium-aluminate-silicate-hydrates (C-A-S-H) dominate the creep magnitude and kinetics. The ongoing pozzolanic reaction of fly ash (FA) significantly increases creep, whereas the formation of foil-like C-A-S-H in slag (SL) blends inhibits its creep, except for the significant early-age creep due to the steep reaction of SL at the corresponding period. The high calcium concentration in cement pore solution delays the further hydration of the clinker, thereby slightly inhibiting the development of creep. The hydration-triggered dissolution of SCM and clinker contributes to creep development, whereas the load-induced dissolution of C-A-S-H may account for aging creep.
{"title":"Does the hydration process of supplementary cementitious materials affect the aging creep of blended cement paste?","authors":"Jiawei Wang , Xiaohong Zhu , Jun Wang , Yang Chen , Yuanpeng Liu , Zhangli Hu , Jiaping Liu , Roya Maboudian , Paulo J.M. Monteiro","doi":"10.1016/j.cemconres.2025.107826","DOIUrl":"10.1016/j.cemconres.2025.107826","url":null,"abstract":"<div><div>In cementitious materials, continuous hydration of mineral phases and creep always coexist, making it difficult to decouple the effect of hydration on creep measurements, which are invariably time-dependent. This study compares a real hydration (aging) system with an equivalent hydration (non-aging) system. In the non-aging system, the unhydrated phase was replaced with inert quartz at specific ages (1, 7, 28, and 91 days) to uncover the mechanism of clinker and supplementary cementitious materials (SCMs) hydration on creep. The results show that the hydration process of SCMs and morphology of calcium-aluminate-silicate-hydrates (C-A-S-H) dominate the creep magnitude and kinetics. The ongoing pozzolanic reaction of fly ash (FA) significantly increases creep, whereas the formation of foil-like C-A-S-H in slag (SL) blends inhibits its creep, except for the significant early-age creep due to the steep reaction of SL at the corresponding period. The high calcium concentration in cement pore solution delays the further hydration of the clinker, thereby slightly inhibiting the development of creep. The hydration-triggered dissolution of SCM and clinker contributes to creep development, whereas the load-induced dissolution of C-A-S-H may account for aging creep.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107826"},"PeriodicalIF":10.9,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378329","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.2025.107822
Brayan Alberto Arenas-Blanco , Anderson Arboleda-Lamus , Mack Cleveland , Perla B. Balbuena , Jeffrey W. Bullard
Calcium sulfate has one of three hydration states, CaSO4∙ x H2O where x equals 0 (anhydrite), 0.5 (bassanite), or 2 (gypsum). Despite numerous investigations of their dissolution in aqueous environments, relatively little is known about the mechanisms at the atomic scale. Here, we shed light on these mechanisms through molecular dynamics simulations of selected surfaces of all three hydrated forms. Umbrella Sampling is used to determine the Potential of Mean Force and to calculate dissolution energy barriers from atomically smooth surfaces with or without one neighboring vacancy and from anhydrite kink sites. The force profiles for Ca2+ and SO42− reveal intermediate steps prior to complete solvation and indicates that the energy barriers are impacted by the mineral's hydrated state, the detaching ion, and any neighboring surface vacancy. Water adsorption on anhydrite and bassanite is influenced by the type of vacancy present, with the SO42− vacancies promoting surface hydration.
{"title":"Dissolution mechanisms of gypsum, bassanite, and anhydrite: A molecular dynamics simulation approach","authors":"Brayan Alberto Arenas-Blanco , Anderson Arboleda-Lamus , Mack Cleveland , Perla B. Balbuena , Jeffrey W. Bullard","doi":"10.1016/j.cemconres.2025.107822","DOIUrl":"10.1016/j.cemconres.2025.107822","url":null,"abstract":"<div><div>Calcium sulfate has one of three hydration states, CaSO<sub>4</sub>∙ <em>x</em> H<sub>2</sub>O where <em>x</em> equals 0 (anhydrite), 0.5 (bassanite), or 2 (gypsum). Despite numerous investigations of their dissolution in aqueous environments, relatively little is known about the mechanisms at the atomic scale. Here, we shed light on these mechanisms through molecular dynamics simulations of selected surfaces of all three hydrated forms. Umbrella Sampling is used to determine the Potential of Mean Force and to calculate dissolution energy barriers from atomically smooth surfaces with or without one neighboring vacancy and from anhydrite kink sites. The force profiles for Ca<sup>2+</sup> and SO<sub>4</sub><sup>2−</sup> reveal intermediate steps prior to complete solvation and indicates that the energy barriers are impacted by the mineral's hydrated state, the detaching ion, and any neighboring surface vacancy. Water adsorption on anhydrite and bassanite is influenced by the type of vacancy present, with the SO<sub>4</sub><sup>2−</sup> vacancies promoting surface hydration.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"191 ","pages":"Article 107822"},"PeriodicalIF":10.9,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143378351","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.2025.107823
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.
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